Landscape to microhabitat: Uncovering the multiscale complexity of native and exotic forests on Terceira Island (Azores, Portugal)

Sébastien Lhoumeau; Rui B Elias; Dominik Seidel; Rosalina Gabriel; Paulo A V Borges

doi:10.1371/journal.pone.0326304

. 2025 Jun 16;20(6):e0326304. doi: 10.1371/journal.pone.0326304

Landscape to microhabitat: Uncovering the multiscale complexity of native and exotic forests on Terceira Island (Azores, Portugal)

Sébastien Lhoumeau ^1,^*, Rui B Elias ¹, Dominik Seidel ², Rosalina Gabriel ¹, Paulo A V Borges ^1,^3,⁴

Editor: Francesco Boscutti,⁵

PMCID: PMC12169593 PMID: 40522958

Abstract

This study aims to identify the structural and compositional differences between native and exotic woodlands on Terceira Island, Azores. Based on landscape, habitat, and microhabitat analyses, remnants of native forests appeared to be associated with less accessible terrains. A more homogeneous structural complexity is exhibited, derived from the numerous branching patterns of the endemic vascular plant species. In contrast, exotic forests exhibit structural heterogeneity driven by mixed non-indigenous vascular plant species as a result of human actions such as afforestation and latter invasion of exotic tree species, after abandonment of the agricultural use. The ground and canopy layers in exotic forests were more invaded by non-indigenous species, while the understory demonstrated greater resilience by being mostly composed of indigenous species. Our findings highlight the structural and ecological differences between native and exotic woodlands, reflecting the historical transformation of forest cover in the Azores. These insights emphasize the importance of long-term monitoring and structural assessments in informing conservation efforts aimed at preserving native forests and managing invasive species in exotic woodlands.

Introduction

Forests play a critical role in maintaining global biodiversity [1,2], regulating the carbon cycle [3,4], and providing a wide range of ecosystem services [5–7] as a result of their structural complexity [7–10]. Forest structure is defined by several components like spatial organization of the trees and shrubs [11], vertical foliage distributions [12], horizontal canopy distribution [13] and amount of dead wood [14,15]. Tree and forest structure can serve as an indicator of tree vitality [16,17] or forest and ecosystem dynamics, helping to track changes driven by natural processes or human activities [10,18]. The structure of forests around the globe is influenced by a multitude of environmental factors, both local and global, including climate, soil characteristics, and species composition, making them complex ecosystems to study [19].

Among the most vulnerable ecosystems are forests found on oceanic islands, where isolation and unique environmental pressures create singular forest dynamics [20,21]. Island ecosystems are often referred to as “natural laboratories” due to their isolation, which leads to the evolution of unique species, communities and ecological interactions. However, these ecosystems are highly sensitive to disturbances such as habitat degradation, invasive species, and climate change [22]. Understanding the structure of forests in island environments is therefore of high relevance both theoretically (see for example [23]) and for conservation purposes (see for example [24]), as these forests tend to house endemic species that rely on specific ecological conditions [25].

Characterising forest structures in island ecosystems like those of the Azores archipelago is therefore crucial for managing biodiversity and assessing ecosystem health. Despite the availability of some work on the environmental drivers determining the forest structure in the neighbouring archipelago of Canary Islands (e.g., [26,27]), few data is available on Azorean forests (see [4]). The Azores, one of the most remote archipelagos in the North Atlantic Ocean, is made up of nine islands shaped by both natural processes and six centuries of human influence [28–30]. These islands are known for their rich biodiversity, unique ecosystems, and varying vegetation types, which include both native and exotic woodlands [28,31].

The native vegetation, part of the archipelago’s natural heritage, consist of several vegetation types [28,32–35] and are home to many endemic taxa [36], not only of vascular plants but also bryophytes [37] and arthropods [38]. However, historical descriptions and paleoecological analyses [30,39–42], provide evidence of the extent and progression of land-use changes since human settlement [43]. Large areas being replaced by exotic species such as Cryptomeria japonica (L. f.) D.Don and Pittosporum undulatum Vent., introduced for commercial forestry [29]. According to the State of the Environment Report of 2022 (Azorean Regional Government), based on a forest inventory from 2007, forest areas occupied 30% of the land surface in the Azores. From these, 31,1% are production forests; 33,4% are Pittosporum dominated woodlands; and 35,5% are natural and seminatural areas (including native forests). i.e., approximately ⅓ for each type. As a result, the Azores’s landscape has several patches of native and exotic woodlands in a matrix of agricultural fields [32,43–45], each contributing differently to the current ecological dynamics of the island. Native vegetation are crucial for maintaining the Azorean island’s biodiversity, acting as refuges for endemic plants and animals [46]. In contrast, Azorean exotic woodlands present a different spatial structure, often lacking the structural complexity and diversity of native forests [47] but see [48]. Understanding how these woodlands differ in terms of structure is essential for assessing their ecological function and resilience to environmental disturbances.

Terceira Island, the third largest of the nine islands in the archipelago is considered to have the best-preserved and most representative native vegetation patches [28,49]. As such, it provides an ideal setting for studying the defining characteristics and structural complexity of both native and exotic woodlands. This study is based on a global and holistic approach to characterise structural complexity of the woodlands. We use LiDAR (Light Detection And Ranging) technology to analyse the structural characteristics of these ecosystems. Furthermore, the use of remote sensing data from satellites and Unmanned Aerial Vehicle (UAV) allows for the acquisition of more detailed information regarding the canopy layer. Finally, the vegetation data collected from surveys provides information on species composition and density across all layers. The data, gathered on Terceira Island, are used to address the following question: What are the defining characteristics of the vegetation structure of the various types of Azorean forests, with a particular focus on the native and exotic woodlands? By answering this question, this study aims to provide a detailed characterisation of Terceira’s forests, offering insights into how both native and exotic forest types are integrated within the island’s broader ecosystem.

Materials and methods

Study area and site selection

This study was conducted on Terceira Island, part of the Azores Archipelago (Portugal, Macaronesia), located in the North Atlantic Ocean approximately 1,500 km west of mainland Portugal (Fig 1). To assess and compare the vegetation structure of native and exotic forests, a total of 18 sites of 20 x 20 m (400m²) were selected (Table S1 in S1 Data). Nine of these sites are located within areas of core native vegetation which are dominated by Juniperus brevifolia (Seub.) Antoine and Ilex azorica Gand. The remaining nine sites were situated in areas dominated by the invasive Pittosporum undulatum. Of the 18 sites, 13 are part of the long-term project SLAM (Long Term Ecological Study of the Impacts of Climate Change in the natural forest of Azores) that started in 2012. Focused on arthropods monitoring, it aims to understand the impact of the drivers of biodiversity erosion on Azorean native forests [51–53].

Fig 1 — Map of the study area on Terceira Island, Azores, showing the location of the 18 forest sites surveyed, including nine within native forest and nine within exotic woodlands. Protected areas are indicated based on data from [50], and land use classifications are provided by the Azorean Government.

Data acquisition

All the necessary permits for data collection were obtained from DRAAC (Direção Regional do Ambiente e Ação Climática) for access to sites in protected areas and from AAN (Autoridade Aeronáutica Nacional) and SRAAC (Secretaria Regional do Ambiente e Ação Climática) for UAV data collection.

Terrestrial laser scanning

LiDAR is a close-range remote sensing tool that produces high-resolution, three-dimensional data on canopy height, vegetation layers, and tree density, making it ideal for forest structure analysis. Here we used a Faro Focus M70 (Faro Technologie Inc., Lake Mary, USA) terrestrial laser scanner mounted on a tripod and operated in single-scan mode to characterise the vegetation structure with established 3D metrics. While the ground-based approach of terrestrial laser scanning is less applicable to large areas when compared to airborne laser scanning, it provides objective and highly-efficient spatial data with very high-resolution even in very dense and structurally complex forests [54–56].

The device is a phase-shift-based 3D laser scanner capturing a field of view of 305–360 degrees vertically and horizontally, respectively. It captures objects in a distance of up to 70 m that reflect the emitted laser light (1050 nm wavelength) at their surface and stores the object’s local coordinates as well as the intensity of the reflected signal. Mounted on a standard tripod at breast height (1.3 m) the scanner rotates and captures the entire scenery in its surroundings creating a so-called point cloud. Using the software Faro Scene (Faro Technologies Inc. Lake Mary, USA), the scan data was filtered for erroneous measurements and converted into txt-file format for further calculation of several forest structural metrics. To capture the forest plots, we conducted five scans per plot. One in the centre and one in each corner of the plot (five-on-a-dice setup) as conducted in earlier studies (e.g., [19,56]. The values of the metrics were ultimately averaged to derive a single mean value for each metric in each plot.

We derived several established metrics for single-scan laser scanning, namely the Stand Structural Complexity Index (SSCI, see [57] for details) including the mean fractal dimension (abbr. mean_FD) and the effective number of layers, the understory complexity index (UCI, see [58] for details), canopy openness (see [59] for details), foliage height diversity (after [60] and adapted to laser scanning as described in [61]). Effective number of layers and vertical evenness were calculated according to [62].

UAV canopy mapping

To assess the fine-scale structure of the forest canopy, we employed the use of an unmanned aerial vehicle (UAV), specifically a DJI Mavic Pro drone, during summer 2024 and in temporal proximity to the laser scanning. Flight missions were planned and executed using the Litchi Mission Hub software, which allowed for precise control over the UAV’s trajectory. The flight plans were designed to cover an area of 30 x 30 meters following a boustrophedon pattern. We slightly expanded the mapped area to minimize distortion effects during the reconstruction process. This approach ensured high-quality RGB imaging with a targeted ground sampling detail of 1 cm per pixel, enabling detailed analysis of the canopy surface.

The collected imagery was processed using Agisoft Metashape (version 1.5.2) software to generate a dense point cloud, providing a 3D representation of the canopy structure. The roughness of the canopy surface was analysed using CloudCompare (version 2.13.2). In this analysis, the “roughness” value was calculated as the distance between each point in the point cloud and the best-fitting plane computed based on its nearest neighbours (radius = 20 cm). The roughness of a structure refers to how smooth or bumpy its surface is. A surface with high roughness has more bumps and irregularities, while a low-roughness surface is smoother. Finally, the point cloud data was rasterized to create a spatially continuous dataset, enabling further quantitative analysis of canopy structure across the study sites.

To quantify the roughness over the plot area, we used QGIS (version 3.34.9) to calculate the average and standard deviation of the roughness values across a 400 m² area for each site. This allowed for a more comprehensive assessment of canopy surface variation within the different forest types, providing insights into structural heterogeneity across the native and exotic forests.

Vegetation survey

This survey aimed to collect detailed data on forest species composition across the study plots. The exotic forest plots were surveyed in the spring of 2023 within 20 x 20 meter plots, while the native forest plots were surveyed earlier, during the summer of 2012 and 2013, within larger 50 x 50 meter plots. Data on woody species within native plots are taken from [63].

Prior to data collection, we conducted a brief field reconnaissance of each site. Although not formally quantified, this visual assessment confirmed that species composition and distribution were remarkably consistent across the entire area of each plot and its surroundings, supporting our use of differing plot sizes without introducing bias in structural complexity estimates. The methodology was firstly designed and implemented in 2012 during earlier projects, notably ISLANDBIODIV and MOVECLIM. The formal publication of the protocol included contributions from multiple specialists and research groups leading to a standardised survey protocol for island biotas [64].

Several important variables were measured during the surveys to assess the forest structure. Species richness (H₀), representing the total number of species present in each plot [65], was recorded to evaluate diversity within the forest plots. The basal area of trees with a diameter at breast height (DBH) greater than 10 cm was calculated per hectare. This measure is important assessing the importance of tree species in the overall forest structure. Finally, we counted the number of all woody vascular plants per species and per square metre in five subplots of 5 x 5 metres, placed in a five-on-a-dice arrangement, which allowed us to assess the vegetation.

These measurements were further classified in three distinct forest strata: the ground layer, the understory, and the canopy, offering a vertical profile of the forest structure. The classification of species as endemic, native, introduced, or invasive follows the regional checklist [36] and updated data from AZORES BIOPORTAL (https://azoresbioportal.uac.pt/). Invasive status is further based on species listed in Decreto-Lei n.º 565/99, de 21 de Dezembro, which identifies legally recognized invasive plants in Portugal, including the Azores. It results in a total of twelve variables, with each stratum and species category providing specific insights into the forest’s ecological composition and structure.

Sites and landscape characteristics

For each of the 18 study sites on Terceira Island, detailed data on elevation and landscape characteristics were collected. Elevation data for each site were extracted using digital elevation models sourced from the Shuttle Radar Topography Mission (SRTM) [66], providing a precise measurement of the elevation at which each plot is located. Moreover, terrain slope was assessed within a quadrat of side 500m using Horn’s method [67] implemented in QGIS software (version 3.34). Mean, minimum, maximum and standard deviation of the slope were assessed.

Furthermore, landscape heterogeneity was quantified in the surrounding area of each site. Land use data, obtained from the Azorean government (https://ot.azores.gov.pt/), were processed and analysed in QGIS. A quadrat of side 500 meters was designed around all plots, and the proportion of land use was assessed per category.

Slopes and land use were computed considering a spatial resolution of 30 meters per pixel.

Data analysis

The dataset used for data analysis is composed of a total of 49 variables describing several features of the forests grouped accordingly to their ecological relevance. Variables are described in the Table S1. All data management and preprocessing steps were conducted using Julia version 1.10 [68], while the NMDS computations and correlation analyses were performed in R version 4.4.1 [69]. This workflow ensured efficient data handling and precise statistical analysis of the complex; multi-variable dataset collected across the study sites.

Patterns in forest structure and composition across the various study sites, was explored using 2D Non-metric Multidimensional Scaling (NMDS) analysis. The NMDS were calculated using the metaMDS function from the vegan package in R [70], based on Bray-Curtis dissimilarity, which is suitable for ecological data with multiple variables. This approach enabled us to simplify the data set while maintaining the underlying ecological relationships, thus facilitating a clear visualisation of the differences between native and exotic forest plots.

A global NMDS was conducted, with all the 49 variables considered. This analysis was complemented by an Analysis of Similarities (ANOSIM) test using the anosim function from the vegan R package, with the objective of evaluating the statistical significance of differences between native and exotic forest plots. ANOSIM is a non-parametric test that is used to compare the dissimilarities between predefined groups. This is achieved by ranking the pairwise distances and generating an R statistic. An R value close to 1 indicates high dissimilarity between groups, whereas an R value near 0 indicates low or no difference. For this study, we used the Bray-Curtis dissimilarity computation and 999 permutations, the two groups considered are the forest types (namely native and exotic forests). Subsequently, for each site, we analyzed the relationship between the position of the plots in the 2D NMDS space and their corresponding traits in the original 49D trait matrix. This was done by computing Spearman’s rank correlation test, implemented via the Hmisc package in R [71]. By correlating the 2D coordinates of the plots in the NMDS space with the original multidimensional trait data, we identify the variables most strongly associated with variations in the forest structure.

Furthermore, each variable was assigned to a group based on its potential ecological explanatory meaning hereafter called traits by following the definition from [72].The following Fig 2 provides a visual representation of the clustering and spatial hierarchical links between the traits. For each of the traits, a NMDS was performed to investigate the ways in which each forest type differs according to the spatial scale under consideration.

Fig 2 — The organisation is based on the spatial extent from landscape scale (Spatial traits) to plot scale (stand traits) micro-habitat (canopy, understory and ground traits).

Results

A global perspective points out that the selected native and exotic plots on Terceira Island exhibited divergent species compositions. Vegetation surveys underscored the prevalence of endemic species in native plots, with most vascular plants occurring in the understory (57 species) and ground strata (49 species), exhibiting notable contributions from endemic and native species (Table 1). By contrast, exotic plots exhibited a more balanced distribution across the strata, with notable numbers recorded in the understory (22 species) and canopy (15 species) (Table 1). Further detailed data can be found in table S5 in S1 Data.

Table 1. Number of vascular plant species recorded in exotic and native plots according to their dominant strata and their colonisation status from [36].

Dominant strata	Colonisation status	Number of species in exotic plots	Number of species in native plots
Ground	Introduced	4	1
	Native	17	49
	Endemic	3	54
	Unknown	2	0
Understory	Invasive	16	13
	Native	22	57
	Endemic	16	41
	Unknown	1	0
Canopy	Invasive	15	1
	Introduced	7	1
	Native	4	1
	Endemic	13	68

Open in a new tab

When added together with the other variables within the global NMDS analysis (Fig 3), we found significant structural differences between native and exotic forest plots. This discrimination of the forest type is visible on the first axis of the NMDS. The ANOSIM resulted in an R statistic of 0.9036 and a significance level of p < 0.001. This high R value, close to 1, indicates strong dissimilarity between the two forest types, with minimal overlap in structural characteristics.

The clustered NMDS analysis based on the forest traits (Fig 4) demonstrated that the plots could be distinctly separated into two groups, corresponding to the forest types in all cases. However, the magnitude of differentiation (R statistics of the ANOSIM) differs according to the trait considered. The greatest differentiation of forest types was obtained using stand traits, while the least differentiation was obtained using ground community traits. Interestingly, at the micro-habitat scale, a gradient of differentiation was observed following the verticality of the layers (Fig 4).

The Table 2 presents the statistically significant variables correlated with the axis of the corresponding NMDS for each trait.

Table 2. Spearman rank correlation coefficients of variables significantly correlated with a NMDS axis for a given forest trait.

Trait	Variable	NMDS axis	Spearman’s correlation coefficient (ρ)	p value
Spatial trait	naturalveg_prop	NMDS1	−0,924	<0,01
Spatial trait	SRTM_elevation	NMDS1	−0,748	<0,01
Spatial trait	slope_std	NMDS1	−0,686	0,002
Spatial trait	slope_max	NMDS1	−0,498	0,035
Spatial trait	pasture_prop	NMDS1	0,558	0,016
Spatial trait	secondaryforest_prop	NMDS1	0,873	<0,01
Spatial trait	pasture_prop	NMDS2	−0,704	0,001
Spatial trait	slope_std	NMDS2	0,476	0,046
Spatial trait	slope_max	NMDS2	0,517	0,028
Spatial trait	slope_mean	NMDS2	0,723	0,001
Spatial trait	slope_min	NMDS2	0,866	<0,01
Stand trait	mean_FD	NMDS1	−0,909	<0,01
Stand trait	H0_VP	NMDS1	−0,788	<0,01
Stand trait	basal_area_endemic	NMDS1	−0,637	0,004
Stand trait	basal_area_introduced	NMDS1	0,586	0,011
Stand trait	ENL0D	NMDS1	0,688	0,002
Stand trait	vertical_evenness	NMDS1	0,71	0,001
Stand trait	basal_area_invasive	NMDS1	0,832	<0,01
Stand trait	ENL2D	NMDS1	0,917	<0,01
Stand trait	ENL1D	NMDS1	0,92	<0,01
Stand trait	foliage_height_diversity	NMDS1	0,92	<0,01
Stand trait	basal_area_native	NMDS2	−0,714	0,001
Canopy community trait	2_endemic	NMDS1	−0,935	<0,01
Canopy community trait	density_2_endemic	NMDS1	−0,896	<0,01
Canopy community trait	density_2_introduced	NMDS1	0,51	0,031
Canopy community trait	2_introduced	NMDS1	0,6	0,009
Canopy community trait	2_invasive	NMDS1	0,776	<0,01
Canopy community trait	density_2_invasive	NMDS1	0,776	<0,01
Canopy community trait	density_2_native	NMDS2	−0,725	0,001
Canopy community trait	2_native	NMDS2	−0,634	0,005
Canopy community trait	canopy_openness	NMDS2	0,882	<0,01
Understory community trait	1_endemic	NMDS1	−0,92	<0,01
Understory community trait	1_native	NMDS1	−0,82	<0,01
Understory community trait	UCI_mean	NMDS1	−0,808	<0,01
Understory community trait	density_1_native	NMDS1	0,806	<0,01
Ground community trait	0_endemic	NMDS1	−0,53	0,024
Ground community trait	density_0_introduced	NMDS2	−0,546	0,019
Ground community trait	0_native	NMDS2	0,755	<0,01
Ground community trait	0_endemic	NMDS2	0,902	<0,01

Open in a new tab

The native forest plots (Fig. 5) were in more complex terrain, characterised by high elevation and slope, and in large, homogeneous areas surrounded by natural vegetation. These stands were structurally complex, principally composed of large and old endemic trees with reduced height. A detailed investigation of the micro-habitats within each layer revealed a structural and compositional homogeneity in the canopy, as well as a high level of pristine composition when considering the endemic tree species. The understory was found to be highly structurally complex, with a diverse range of indigenous (native and endemic) plant species. Finally, the ground layer is mainly occupied by indigenous vascular plants.

In contrast, exotic forest plots (Fig. 5) were in areas with more convenient access, situated within a mosaic of human-influenced landscapes. The stands exhibited a high and multi-layered structure. It is also noteworthy that, in comparison to native forest plots, these plots exhibited greater heterogeneity in their structure and composition. This heterogeneity is also evident in the canopy layer. Despite the dominance of introduced and invasive species, the canopy openness was also identified as a statistically significant variable associated with the separation of plots. The understory was dominated by native species and exhibited a lower structural complexity compared to the native forest plots. The ground layer demonstrated a clear dominance of introduced species.

Discussion

We aimed to provide a detailed characterisation of the native and exotic woodlands on Terceira Island (Azores, Portugal). It was found that these forest types exhibited structural and compositional differences at different spatial scales. Furthermore, our study brings insights into the potential of forest structure as an indicator of ecological disturbance and invasion patterns, particularly in island ecosystems where native flora and fauna face unique vulnerabilities [22,73]. By analysing forest traits from the microhabitat to the landscape, our results reveal a multi-layered understanding of the ways in which both intrinsic ecological factors and external disturbances shape Azorean forests. The findings of this study highlight the necessity of examining forest structure at various spatial scales, as the differentiation between native and exotic forests exhibited significant variation depending on the spatial level under consideration.

Landscape-level structure is a consequence of human accessibility and land-use

At the landscape level, spatial traits demonstrated a robust correlation between exotic forests and human-modified regions, whereas native forests exhibited a greater prevalence in remote, complex terrain. This pattern is common to all the Macaronesian islands [74], in which native forest is now restricted to more complex orographic terrains, being relics of past dramatic native forest clearing. This spatial distribution not only reflects the influence of human accessibility as a driver of ecosystem change [74], but also points to the role of historical land-use patterns, documented through both ecological studies [28] and historical accounts [39–41] which have progressively restricted native forests to higher elevations. Therefore, it is probable that the selected native forest plots, which are less accessible, have experienced a reduced number of direct disturbances over time, thereby preserving their structural complexity.

Moreover, the current fragments of Terceira’s native forest are now under protection, part of integral natural reserves. Creation of protected areas is known to reduce the human impact (see for example [75,76]) but it must be based on a correct spatial distribution, otherwise the effectiveness of their protection is limited (see examples in [77–79]). However, all over the world, islands still face significant ecological challenges due to invasive plant species spread [22,80], and in the Azores several invasive plants are spreading in native forest [81,82]. In the current study, the selected nine plots of native forest in Terceira Island were chosen based on their high level of natural condition. However, despite the results obtained reflecting low levels of disturbance, some invasive plants are already spreading in some plots. For example, the spread of species such as Pittosporum undulatum (Australian cheesewood) or Hedychium gardnerianum (Ginger lily) has resulted in the decline of native flora and fauna in numerous native forest areas across several Azorean islands, particularly due to alterations in species interaction networks [83,84]. This impact is particularly concerning for the ecosystem of the Azores, which has evolved in isolation and where many plants and animals are not adapted to compete with aggressive newcomers [85]. Thus, while the forests are now protected, active management, like removing invasive species and restoring native vegetation, remains crucial to maintaining their health and resilience, which is being currently implemented under the scope of several LIFE projects (e.g., LIFE BEETLES [86]).

By contrast, exotic forests, which have been established in more easy-to-access areas, exhibit spatial traits that align with historical human activity and land-use change. Since settlement began approximately 500 years ago [41], human presence on Terceira Island has led to the intentional and unintentional introduction of non-native species, particularly in forests accessible for resource extraction and agriculture [87]. The enhanced accessibility has facilitated the widespread transformation of landscapes, where indigenous species were initially displaced through land-use change, and later further impacted by the expansion of exotic and invasive species into these disturbed areas [74]. Indeed, the non-indigenous tree species reported in these ecosystems, such as Pittosporum undulatum and Cryptomeria japonica, were introduced by humans for economic reasons [4,88]. In particular, P. undulatum, the dominant species in our exotic plot, was introduced to the Azores as a windbreak to protect the fruit orchards [89]. When production decreased, the orchards were abandoned, and this species, with dispersal potential in the Azores [90], proliferated, creating a mosaic of secondary woodlands among pastures.

These large historical changes at the landscape scale can cascade down to finer structural changes at stand and microhabitat levels. Interestingly, some of these invaded areas still hold rare endemic arthropods, with relict populations surviving in these remnants [48].

The structural complexity of forest stands is derived from different sources in native and exotic woodlands

Contrary to expectations, the Stand Structural Complexity Index (SSCI) was not identified as a statistically significant variable differentiating our native and exotic plots. Given its established use in numerous studies aimed at characterising structural differences linked to forest management [54,57], we would have expected this composite index to be a primary criterion for distinguishing between forest types.

It must be assumed that this is a consequence of the methodology employed in the construction of the index. The SSCI is defined as an exponential combination of the fractal dimension index (mean_FD, as defined by [91]) and the effective number of layers (ENL1D, as defined by [62]), which encompass the stand height for the purposes of providing a scaling component. However, mean_FD was identified as a relevant indicator for describing native stands, whereas ENL1D was associated with exotic woodlands. It can be inferred that SSCI will exhibit comparable values between the two forest types, limiting its use in distinguishing between native and exotic forests in the Azores. The similar values obtained for this composite index indicate that the structural complexity may have originated from different origins.

The intrinsic complexity of native stands may be attributed to the traits of the few endemic tree species (e.g., the Azorean endemic cedar Juniperus brevifolia), which exhibit greater branch ramifications, as well as the numerous non-vascular epiphytic species, resulting in a higher fractal dimension. Conversely, the structural complexity observed in exotic woodlands is likely to be the consequence of the mixture of invasive and introduced species and the overall greater height affecting the scaling-component of the SSCI index. Indeed, non-indigenous tree species were selected based on their capacity for rapid growth and their tendency to reach considerable heights, with the objective of utilising them as windbreaks. Consequently, exotic woodlands exhibit higher stand height, which allows for the development of a greater number of layers positively affecting the SSCI.

The canopy of native forests shows greater structural and compositional homogeneity

The structure of forest canopies drives habitat specialisation and species richness [92,93]. Thus, a particular interest must be dedicated to this microhabitat.

The canopy of the native forests on Terceira exhibits a high degree of structural and compositional consistency. This homogeneity likely stems from the evolutionary adaptations of endemic species to environmental conditions above 500–600 m namely lower temperatures, higher winds and rainfall, and poor soils [28,94]. Consequently, their canopy architecture and slower growth rates contribute to a dense, closed canopy. Following the environmental filtering theory, that may resist the establishment of invasive species, at least with current environmental conditions, since the impact of climatic changes may reverse the current situation (see [95]). In contrast, the exotic forests, composed of various introduced species, display greater structural variation and openness, particularly in the canopy. This structural diversity could be a result of a human-induced species replacement, resulting in the introduction of species with differing growth habits and ecological strategies. It is also important to consider that the observed structural heterogeneity in exotic forests may partly reflect their younger age and earlier successional stage relative to native forests. However, given their dominance by fast-growing invasive species and history of colonizing previously disturbed areas, this heterogeneity also reflects ongoing ecological dynamics that may not necessarily lead to convergence with native forest structure over time.

Interestingly, canopy roughness did not emerge as a significant variable of differentiation. This finding could reflect the role of consistent environmental factors, such as wind, that shape the canopy structure of both forest types in similar ways, regardless of species composition. Alternatively, the similarity in canopy roughness might suggest that while exotic species have replaced the original native canopy, they exhibit similar spatial configurations, at least from above, possibly due to historical human selection of species suited to local environmental conditions.

Structural vulnerability varies between microhabitats

Our study highlights that structural vulnerability to invasion differs across forest layers.

The ground layer appears to be the most susceptible to initial invasions, as evidenced by the high density of introduced species in exotic forest plots. Similar pattern was found in arthropods taxon which present a lower biotic integrity in the epigeal community of native forests [86]. This susceptibility can be attributed to several factors, including the greater availability of resources and the presence of vacant ecological niches in the ground layer, which provide fewer competitive barriers for incoming species. Furthermore, higher propagule pressure due to the proximity with other types of ecosystems [47,48], contributes to the rapid establishment and dominance of introduced species with superior effective spreading abilities in the ground layer of exotic forests.

The canopy layer of Azorean forests appears to be the least vulnerable microhabitat. In exotic forests, it is dominated by invasive species such as Pittosporum undulatum, which has competitive advantages [96,97]. In the absence of targeted restoration measures, this dominance limits the possibility of native species re-establishment, effectively locking the canopy into a state of low biodiversity and limited structural resilience. The species produces a substantial quantity of foliage, which creates a dense canopy that effectively excludes the growth of other understory species [96]. In contrast, the native forest canopy, distinguished by its closed structure and prevalence of a few complex endemic species, is inherently less susceptible to invasion. These climax communities, with their dense canopy architecture, provide few opportunities for new species to establish in the absence of significant natural or human-induced disturbances [97,98]. However, the inherent unsaturation of island forest communities – a condition where ecological niches remain unfilled – renders them susceptible to species packing following human introductions [20]. Any change in the structural complexity of these canopies, whether through disturbance or invasive dominance, would signify severe ecological shifts, altering habitat availability and impacting the broader ecosystem.

Beyond the dominance of Pittosporum undulatum in the canopy, our results reveal that exotic forests also harbour a diversity of introduced and invasive species in the lower layers. This pattern suggests a multi-invasion dynamic, where non-native species colonize distinct forest strata, potentially interacting and reinforcing structural and compositional shifts across vertical layers [99]. Such stratified invasions may accelerate ecological transformation by altering resource availability, microclimate, and species interactions at multiple levels within the forest, highlighting the complexity of managing biological invasions in island ecosystems.

Moreover, the understory layer in exotic forests shows greater resistance to invasion compared to the ground and canopy layers. This observation was also identified during the development of an Index of Biotic Integrity based on arthropod community composition [100]. It may be attributed to the competition with the high density of established native species or the existence of mutualistic relationships between indigenous species that reinforce the ecosystem’s robustness. The understory may serve as a resilient microhabitat in the face of ecological disturbance, particularly the relative integrity of this microhabitat in the exotic plot may be attributed to the refuge function that this ecosystem provides for arthropods, as described by [48]. However, it is noteworthy that the structural complexity of this layer is already disturbed, as the exotic forest showed the lowest values for the Understory Complexity Index (UCI_mean).

Temporal dynamics and conservation implications of forest change

Whilst it is acknowledged that a temporal discrepancy between vegetation surveys for native forest plots may potentially influence comparisons of species composition, it is considered that this impact is negligible in this context. The native forests of the Azores, specifically those selected for this study, are situated in well-preserved and minimally disturbed areas within protected reserves [28]. These ecosystems are characterised by their ecological stability and slow successional dynamics [46], as they are dominated by long-lived endemic tree species [28,33] and exhibit limited exposure to human-induced pressures [74]. By contrast, exotic forest ecosystems are characterised by important dynamism, manifesting in both species composition and structural diversity, owing to the spatial heterogeneity in the surrounding environment [101,102]. Consequently, exotic forests are more prone to rapid change over short timescales, whereas native forests are expected to maintain a relatively consistent structural and compositional profile over the decade separating the surveys. Future long-term monitoring would be valuable to further validate these hypotheses.

These findings, while derived exclusively from Terceira Island, hold valuable implications for forest conservation across the Azores. Although extrapolation to other islands should be made with caution, the structural and compositional trends observed are likely to be applicable to similar forest types elsewhere in the archipelago as Terceira hosts some of the most representative and best-preserved remnants of native forest [103,104]. This ecosystem, with its intrinsic complexity and resistance to invasion, act as crucial biodiversity reservoirs [46].

Conservation efforts should prioritize protecting less accessible areas where native species have a competitive advantage. Conversely, restoration in exotic forests should aim to enhance structural resilience by controlling invasive species, particularly in the ground and canopy layers, while promoting native species to improve overall habitat quality. Conservation efforts should prioritize protecting less accessible areas where native species have a competitive advantage. Conversely, restoration in exotic forests should aim to enhance structural resilience by controlling invasive species, particularly in the ground and canopy layers, while promoting native species to improve overall habitat quality.

Supporting information

S1 Data. Pre-processed data used during analysis.

(ZIP)

pone.0326304.s001.zip^{(135.5KB, zip)}

Acknowledgments

We thank Fernando Pereira and Maria Teresa Fereira for their contribution during the vegetation survey in native forest. We would like to express our gratitude to Brais Casal, Juan Barrajo, Juan Carlos dos Santos, Martha Martínez and Robert Marian for their invaluable assistance during the plant inventory in the exotic plots. We would also like to acknowledge Dirk Böttger, Michael Unger and Paul Konrad Seidel for their help during the LiDAR fieldwork.

Data Availability

Data are available in supplementary materials.

Funding Statement

S.L. is funded by the Azorean Government Ph.D. grant numbers M3.1.a/F/012/2022. R.B.E, R.G., and P.A.V.B. are currently funded by the projects Azores DRCT Pluriannual Funding (M1.1.A/INFRAEST CIENT/001/2022) and FCT—Fundação para a Ciência e Tecnologia FCT-UIDB/00329/2023 DOI 10.54499/UIDB/00329/2020. D.S received no outside funding.

References

1.Wildermuth B, Dönges C, Matevski D, Penanhoat A, Seifert CL, Seidel D, et al. Tree species identity, canopy structure and prey availability differentially affect canopy spider diversity and trophic composition. Oecologia. 2023;203(1–2):37–51. doi: 10.1007/s00442-023-05447-1 [DOI] [PMC free article] [PubMed] [Google Scholar]
2.Renner SC, Gossner MM, Ayasse M, Böhm S, Teuscher M, Weisser WW, et al. Forest structure, plants, arthropods, scale, or birds’ functional groups: What key factor are forest birds responding to?. PLoS One. 2024;19(5):e0304421. doi: 10.1371/journal.pone.0304421 [DOI] [PMC free article] [PubMed] [Google Scholar]
3.Sedjo RA. The carbon cycle and global forest ecosystem. Water Air Soil Pollut. 1993;70(1–4):295–307. doi: 10.1007/bf01105003 [DOI] [Google Scholar]
4.Borges Silva LC, Pavão DC, Elias RB, Moura M, Ventura MA, Silva L. Taxonomic, structural diversity and carbon stocks in a gradient of island forests. Sci Rep. 2022;12(1):1038. doi: 10.1038/s41598-022-05045-w [DOI] [PMC free article] [PubMed] [Google Scholar]
5.Thompson ID, Okabe K, Tylianakis JM, Kumar P, Brockerhoff EG, Schellhorn NA, et al. Forest biodiversity and the delivery of ecosystem goods and services: translating science into policy. BioScience. 2011;61(12):972–81. doi: 10.1525/bio.2011.61.12.7 [DOI] [Google Scholar]
6.Zellweger F, Coomes D, Lenoir J, Depauw L, Maes SL, Wulf M, et al. Seasonal drivers of understorey temperature buffering in temperate deciduous forests across Europe. Glob Ecol Biogeogr. 2019;28(12):1774–86. doi: 10.1111/geb.12991 [DOI] [PMC free article] [PubMed] [Google Scholar]
7.Verheyen K, Gillerot L, Blondeel H, De Frenne P, De Pauw K, Depauw L, et al. Forest canopies as nature‐based solutions to mitigate global change effects on people and nature. Journal of Ecology. 2024;112(11):2451–61. doi: 10.1111/1365-2745.14345 [DOI] [Google Scholar]
8.Martinez-Almoyna C, Calderòn-Sanou I, Lionnet C, Gielly L, Boyer F, Dufour P, et al. Vegetation structure and climate shape mountain arthropod distributions across trophic levels. J Anim Ecol. 2024;93(10):1510–23. doi: 10.1111/1365-2656.14164 [DOI] [PubMed] [Google Scholar]
9.Schwarz J, Habel JC, Eberle J. Effects of habitat biotic features on hymenopteran diversity in East Africa. J Insect Conserv. 2024;28(4):821–30. doi: 10.1007/s10841-024-00604-0 [DOI] [Google Scholar]
10.Wildermuth B, Penanhoat A, Sennhenn-Reulen H, Matevski D, Drescher J, Aubry-Kientz M, et al. Canopy structure influences arthropod communities within and beyond tree identity effects: Insights from combining LiDAR data, insecticidal fogging and machine learning regression modelling. Ecological Indicators. 2024;160:111901. doi: 10.1016/j.ecolind.2024.111901 [DOI] [Google Scholar]
11.Storch F, Dormann CF, Bauhus J. Quantifying forest structural diversity based on large-scale inventory data: a new approach to support biodiversity monitoring. For Ecosyst. 2018;5(1). doi: 10.1186/s40663-018-0151-1 [DOI] [Google Scholar]
12.Seidel D, Ehbrecht M, Dorji Y, Jambay J, Ammer C, Annighöfer P. Identifying architectural characteristics that determine tree structural complexity. Trees. 2019;33(3):911–9. doi: 10.1007/s00468-019-01827-4 [DOI] [Google Scholar]
13.Pelt RV, Franklin JF. Influence of canopy structure on the understory environment in tall, old-growth, conifer forests. Can J For Res. 2000;30(8):1231–45. doi: 10.1139/x00-050 [DOI] [Google Scholar]
14.Li Y, Li M, Li X, Liu Z, Ming A, Lan H, et al. The abundance and structure of deadwood: a comparison of mixed and thinned chinese fir plantations. Front Plant Sci. 2021;12:614695. doi: 10.3389/fpls.2021.614695 [DOI] [PMC free article] [PubMed] [Google Scholar]
15.Bouget C, Cours J, Larrieu L, Parmain G, Müller J, Speckens V, et al. Trait-based response of deadwood and tree-related microhabitats to decline in temperate lowland and montane forests. Ecosystems. 2023;27(1):90–105. doi: 10.1007/s10021-023-00875-9 [DOI] [Google Scholar]
16.Heidenreich MG, Seidel D. Assessing forest vitality and forest structure using 3d data: a case study from the hainich national park, Germany. Front For Glob Change. 2022;5. doi: 10.3389/ffgc.2022.929106 [DOI] [Google Scholar]
17.Heidenreich MG, Höwler K, Seidel D. Towards an objective assessment of tree vitality: a case study based on 3D laser scanning. Trees. 2024;38(4):927–40. doi: 10.1007/s00468-024-02525-6 [DOI] [Google Scholar]
18.Höwler K, Vallebuona N, Wern T, Ammer C, Seidel D. Structural reorganization in beech forests in central Germany as response to drought-induced mortality in the overstory. Trees, Forests and People. 2024;15:100506. doi: 10.1016/j.tfp.2024.100506 [DOI] [Google Scholar]
19.Ehbrecht M, Seidel D, Annighöfer P, Kreft H, Köhler M, Zemp DC, et al. Global patterns and climatic controls of forest structural complexity. Nat Commun. 2021;12(1):519. doi: 10.1038/s41467-020-20767-z [DOI] [PMC free article] [PubMed] [Google Scholar]
20.Mueller-Dombois D. The formation of island ecosystems. GeoJournal. 1992;28(2). doi: 10.1007/bf00177244 [DOI] [Google Scholar]
21.Kamijo T, Kitayama K, Sugawara A, Urushimichi S, Sasai K. Primary succession of the warm-temperate broad-leaved forest on a volcanic island, Miyake-jima, Japan. Folia Geobot. 2002;37(1):71–91. doi: 10.1007/bf02803192 [DOI] [Google Scholar]
22.Fernández-Palacios JM, Kreft H, Irl SDH, Norder S, Ah-Peng C, Borges PAV, et al. Scientists’ warning - The outstanding biodiversity of islands is in peril. Glob Ecol Conserv. 2021;31:e01847. doi: 10.1016/j.gecco.2021.e01847 [DOI] [PMC free article] [PubMed] [Google Scholar]
23.Keppel G, Buckley YM, Possingham HP. Drivers of lowland rain forest community assembly, species diversity and forest structure on islands in the tropical South Pacific. Journal of Ecology. 2009;98(1):87–95. doi: 10.1111/j.1365-2745.2009.01595.x [DOI] [Google Scholar]
24.Helmer E, Ramos O, López TDM, Quinones M, Diaz W. Mapping the forest type and land cover of Puerto Rico, a component of the Caribbean biodiversity hotspot. Caribbean Journal of Science. 2002;38(3–4):165–83. Available from: https://research.fs.usda.gov/treesearch/30146 [Google Scholar]
25.Benavides Rios E, Sadler J, Graham L, Matthews TJ. Species distribution models and island biogeography: Challenges and prospects. Global Ecology and Conservation. 2024;51:e02943. doi: 10.1016/j.gecco.2024.e02943 [DOI] [Google Scholar]
26.Bermúdez AM, Fernández-Palacios JM, González-Mancebo JM, Patiño J, Arévalo JR, Otto R, et al. Floristic and structural recovery of a laurel forest community after clear-cutting: A 60 years chronosequence on La Palma (Canary Islands). Ann For Sci. 2007;64(1):109–19. doi: 10.1051/forest:2006094 [DOI] [Google Scholar]
27.Bello-Rodríguez V, Cubas J, Del Arco MJ, Martín JL, González-Mancebo JM. Elevational and structural shifts in the treeline of an oceanic island (Tenerife, Canary Islands) in the context of global warming. International Journal of Applied Earth Observation and Geoinformation. 2019;82:101918. doi: 10.1016/j.jag.2019.101918 [DOI] [Google Scholar]
28.Elias RB, Gil A, Silva L, Fernández-Palacios JM, Azevedo EB, Reis F. Natural zonal vegetation of the Azores Islands: characterization and potential distribution. phyto. 2016;46(2):107–23. doi: 10.1127/phyto/2016/0132 [DOI] [Google Scholar]
29.Rull V, Lara A, Rubio-Inglés MJ, Giralt S, Gonçalves V, Raposeiro P, et al. Vegetation and landscape dynamics under natural and anthropogenic forcing on the Azores Islands: A 700-year pollen record from the São Miguel Island. Quaternary Science Reviews. 2017;159:155–68. doi: 10.1016/j.quascirev.2017.01.021 [DOI] [Google Scholar]
30.Connor SE, van Leeuwen JFN, Rittenour TM, van der Knaap WO, Ammann B, Björck S. The ecological impact of oceanic island colonization – a palaeoecological perspective from the Azores. Journal of Biogeography. 2012;39(6):1007–23. doi: 10.1111/j.1365-2699.2011.02671.x [DOI] [Google Scholar]
31.Tutin TG. The Vegetation of the Azores. The Journal of Ecology. 1953;41(1):53. doi: 10.2307/2257099 [DOI] [Google Scholar]
32.Dias E, Mendes C, Melo C, Pereira D, Elias R. Azores central islands vegetation and flora field guide. Quercetea. 2005;7:123–73. [Google Scholar]
33.Dias E, Mendes C, Aguiar C. Vegetação dos Açores. In: Capelo J, Aguiar C, editors. Árvores e florestas de Portugal. Lisboa: Imprensa Nacional-Casa da Moeda. 2021. p. 155–79. [Google Scholar]
34.Mucina L, Bültmann H, Dierßen K, Theurillat J, Raus T, Čarni A, et al. Vegetation of Europe: hierarchical floristic classification system of vascular plant, bryophyte, lichen, and algal communities. Applied Vegetation Science. 2016;19(S1):3–264. doi: 10.1111/avsc.12257 [DOI] [Google Scholar]
35.Fernández Prieto JA, Aguiar C, Dias E. Description of some new syntaxa from the Azores archipelago. International Journal of Geobotanical Research. 2012;2:111–6. [Google Scholar]
36.Borges PAV, Costa A, Regina C, Gabriel R, Gonçalves V, Frias Martins A. A list of the terrestrial and marine biota from the Azores. Parede: Principia. 2010. [Google Scholar]
37.Gabriel R, Bates JW. Bryophyte community composition and habitat specificity in the natural forests of Terceira, Azores. Plant Ecol. 2005;177(1):125–44. doi: 10.1007/s11258-005-2243-6 [DOI] [Google Scholar]
38.Borges PAV, Lamelas-Lopez L, Andrade R, Lhoumeau S, Vieira V, Soares AO, et al. An updated checklist of Azorean arthropods (Arthropoda). Biodivers Data J. 2022;10:e97682. doi: 10.3897/BDJ.10.e97682 [DOI] [PMC free article] [PubMed] [Google Scholar]
39.Raposeiro PM, Hernández A, Pla-Rabes S, Gonçalves V, Bao R, Sáez A, et al. Climate change facilitated the early colonization of the Azores Archipelago during medieval times. Proc Natl Acad Sci U S A. 2021;118(41):e2108236118. doi: 10.1073/pnas.2108236118 [DOI] [PMC free article] [PubMed] [Google Scholar]
40.Rull V. Settlement and anthropization of the Azores Islands. Journal of Biogeography. 2023;50(12):2008–11. doi: 10.1111/jbi.14712 [DOI] [Google Scholar]
41.Elias RB, Connor SE, Góis-Marques CA, Schaefer H, Silva L, Sequeira MM, et al. Is there solid evidence of widespread landscape disturbance in the Azores before the arrival of the Portuguese?. Proc Natl Acad Sci U S A. 2022;119(4):e2119218119. doi: 10.1073/pnas.2119218119 [DOI] [PMC free article] [PubMed] [Google Scholar]
42.Connor SE, Lewis T, van Leeuwen JFN, van der Knaap WO, Schaefer H, Porch N, et al. Original plant diversity and ecosystems of a small, remote oceanic island (Corvo, Azores): Implications for biodiversity conservation. Biological Conservation. 2024;291:110512. doi: 10.1016/j.biocon.2024.110512 [DOI] [Google Scholar]
43.Castanho RA, Naranjo Gómez JM, Couto G, Pimentel P, Sousa Á, Batista M da G. Analyzing the Patterns, Trends and Dynamics of the Land-Use Changes in Azores Region: From 1990 to 2018. Sustainability. 2021;13(10):5433. doi: 10.3390/su13105433 [DOI] [Google Scholar]
44.Dias E, Elias RB, Nunes V. Vegetation mapping and nature conservation: a case study in Terceira Island (Azores). Biodiversity and Conservation. 2004;13(8):1519–39. doi: 10.1023/b:bioc.0000021326.50170.66 [DOI] [Google Scholar]
45.Triantis KA, Borges PAV, Ladle RJ, Hortal J, Cardoso P, Gaspar C, et al. Extinction debt on oceanic islands. Ecography. 2010;33(2):285–94. doi: 10.1111/j.1600-0587.2010.06203.x [DOI] [Google Scholar]
46.Lhoumeau S, Borges PAV. Assessing the Impact of Insect Decline in Islands: Exploring the Diversity and Community Patterns of Indigenous and Non-Indigenous Arthropods in the Azores Native Forest over 10 Years. Diversity. 2023;15(6):753. doi: 10.3390/d15060753 [DOI] [Google Scholar]
47.Borges PAV, Lamelas-Lopez L, Stüben PE, Ros-Prieto A, Gabriel R, Boieiro M, et al. SLAM Project - Long Term Ecological Study of the Impacts of Climate Change in the Natural Forest of Azores: II - A survey of exotic arthropods in disturbed forest habitats. Biodivers Data J. 2022;10:e81410. doi: 10.3897/BDJ.10.e81410 [DOI] [PMC free article] [PubMed] [Google Scholar]
48.Tsafack N, Fattorini S, Boieiro M, Rigal F, Ros-Prieto A, Ferreira MT, et al. The Role of Small Lowland Patches of Exotic Forests as Refuges of Rare Endemic Azorean Arthropods. Diversity. 2021;13(9):443. doi: 10.3390/d13090443 [DOI] [Google Scholar]
49.Henriques D, Elias RB, Coelho MCM, Hernandéz RH, Pereira FEA, Gabriel R. Long-term monitoring across elevational gradients (III): vascular plants on Terceira Island (Azores) transect. 2017. [cited 25 Feb 2025]. Available from: http://hdl.handle.net/10400.3/4477 [Google Scholar]
50.UNEP-WCMC. Protected Area Profile for Portugal from the World Database on Protected Areas. 2025. Available from: www.protectedplanet.net [Google Scholar]
51.Costa R, Borges PAV. SLAM project - long term ecological study of the impacts of climate change in the natural forest of azores: i - the spiders from native forests of terceira and pico Islands (2012-2019). Biodivers Data J. 2021;9:e69924. doi: 10.3897/BDJ.9.e69924 [DOI] [PMC free article] [PubMed] [Google Scholar]
52.Lhoumeau S, Cardoso P, Costa R, Boieiro M, Malumbres-Olarte J, Amorim I, et al. SLAM Project - long term ecological study of the impacts of climate change in the natural forest of Azores: IV - The spiders of Terceira and Pico Islands (2019-2021) and general diversity patterns after ten years of sampling. BDJ. 2022;10. doi: 10.3897/bdj.10.e96442 [DOI] [PMC free article] [PubMed] [Google Scholar]
53.Lhoumeau S, Cardoso P, Boieiro M, Ros-Prieto A, Costa R, Lamelas-Lopez L, et al. SLAM Project - long term ecological study of the impacts of climate change in the natural forests of Azores: V - New records of terrestrial arthropods after ten years of SLAM sampling. Biodivers Data J. 2022;10:e97952. doi: 10.3897/BDJ.10.e97952 [DOI] [PMC free article] [PubMed] [Google Scholar]
54.Seidel D, Stiers M, Ehbrecht M, Werning M, Annighöfer P. On the structural complexity of central European agroforestry systems: a quantitative assessment using terrestrial laser scanning in single-scan mode. Agroforest Syst. 2021;95(4):669–85. doi: 10.1007/s10457-021-00620-y [DOI] [Google Scholar]
55.Parada-Díaz J, Fernández López ÁB, Gómez González LA, del Arco Aguilar MJ, González-Mancebo JM. Assessing the usefulness of LiDAR for monitoring the structure of a montane forest on a subtropical oceanic Island. Remote Sensing. 2022;14(4):994. doi: 10.3390/rs14040994 [DOI] [Google Scholar]
56.Soto DP, Salas-Eljatib C, Donoso PJ, Hernández-Moreno Á, Seidel D, D’Amato AW. Impacts of varying precipitation regimes upon the structure, spatial patterns, and productivity of Nothofagus pumilio-dominated old-growth forests in Patagonia. Forest Ecology and Management. 2022;524:120519. doi: 10.1016/j.foreco.2022.120519 [DOI] [Google Scholar]
57.Ehbrecht M, Schall P, Ammer C, Seidel D. Quantifying stand structural complexity and its relationship with forest management, tree species diversity and microclimate. Agricultural and Forest Meteorology. 2017;242:1–9. doi: 10.1016/j.agrformet.2017.04.012 [DOI] [Google Scholar]
58.Willim K, Stiers M, Annighöfer P, Ammer C, Ehbrecht M, Kabal M, et al. Assessing understory complexity in beech-dominated forests (Fagus sylvatica L.) in central europe-from managed to primary forests. Sensors (Basel). 2019;19(7):1684. doi: 10.3390/s19071684 [DOI] [PMC free article] [PubMed] [Google Scholar]
59.Zheng G, Moskal LM, Kim S-H. Retrieval of Effective Leaf Area Index in Heterogeneous Forests With Terrestrial Laser Scanning. IEEE Trans Geosci Remote Sensing. 2013;51(2):777–86. doi: 10.1109/tgrs.2012.2205003 [DOI] [Google Scholar]
60.MacArthur RH, MacArthur JW. On bird species diversity. Ecology. 1961;42(3):594–8. doi: 10.2307/1932254 [DOI] [Google Scholar]
61.Seidel D, Ehbrecht M, Puettmann K. Assessing different components of three-dimensional forest structure with single-scan terrestrial laser scanning: A case study. Forest Ecology and Management. 2016;381:196–208. doi: 10.1016/j.foreco.2016.09.036 [DOI] [Google Scholar]
62.Ehbrecht M, Schall P, Juchheim J, Ammer C, Seidel D. Effective number of layers: A new measure for quantifying three-dimensional stand structure based on sampling with terrestrial LiDAR. Forest Ecology and Management. 2016;380:212–23. doi: 10.1016/j.foreco.2016.09.003 [DOI] [Google Scholar]
63.Borges PAV, Cardoso P, Fattorini S, Rigal F, Matthews TJ, Di Biase L, et al. Community structure of woody plants on islands along a bioclimatic gradient. Frontiers of Biogeography. 2018;10(3–4). doi: 10.21425/f5fbg40295 [DOI] [Google Scholar]
64.Borges PAV, Cardoso P, Kreft H, Whittaker RJ, Fattorini S, Emerson BC, et al. Global Island Monitoring Scheme (GIMS): a proposal for the long-term coordinated survey and monitoring of native island forest biota. Biodivers Conserv. 2018;27(10):2567–86. doi: 10.1007/s10531-018-1553-7 [DOI] [Google Scholar]
65.Hill MO. Diversity and Evenness: A Unifying Notation and Its Consequences. Ecology. 1973;54(2):427–32. doi: 10.2307/1934352 [DOI] [Google Scholar]
66.OpenTopography. Shuttle Radar Topography Mission (SRTM) Global. OpenTopography; 2013. doi: 10.5069/G9445JDF [DOI]
67.Horn BKP. Hill shading and the reflectance map. Proceedings of the IEEE. 2008;69(1):14–47. 10.1109/PROC.1981.11918 [DOI] [Google Scholar]
68.Bezanson J, Edelman A, Karpinski S, Shah VB. Julia: A Fresh Approach to Numerical Computing. SIAM Rev. 2017;59(1):65–98. doi: 10.1137/141000671 [DOI] [Google Scholar]
69.R Core Team. R: A Language and Environment for Statistical Computing. Vienna, Austria: R Foundation for Statistical Computing; 2023. Available from: https://www.R-project.org/ [Google Scholar]
70.Oksanen J, Kindt R, O’Hara B. The vegan package, Community ecology package. 2005. [Google Scholar]
71.Harrell FE. Hmisc: Harrell Miscellaneous. 2024. Available from: https://CRAN.R-project.org/package=Hmisc [Google Scholar]
72.Nock CA, Vogt RJ, Beisner BE. Functional Traits. 1st ed. In: John Wiley & Sons, Ltd, editor. eLS. 1st ed. Wiley; 2016. pp. 1–8. doi: 10.1002/9780470015902.a0026282 [DOI] [Google Scholar]
73.Borges PAV, Gabriel R, Fattorini S. Biodiversity Erosion: Causes and Consequences. Encyclopedia of the UN Sustainable Development Goals. Springer International Publishing. 2019. p. 1–10. doi: 10.1007/978-3-319-71065-5_78-1 [DOI] [Google Scholar]
74.Norder SJ, de Lima RF, de Nascimento L, Lim JY, Fernández-Palacios JM, Romeiras MM, et al. Global change in microcosms: Environmental and societal predictors of land cover change on the Atlantic Ocean Islands. Anthropocene. 2020;30:100242. doi: 10.1016/j.ancene.2020.100242 [DOI] [Google Scholar]
75.Cazalis V, Princé K, Mihoub J-B, Kelly J, Butchart SHM, Rodrigues ASL. Effectiveness of protected areas in conserving tropical forest birds. Nat Commun. 2020;11(1):4461. doi: 10.1038/s41467-020-18230-0 [DOI] [PMC free article] [PubMed] [Google Scholar]
76.Rahman MF, Islam K. Effectiveness of protected areas in reducing deforestation and forest fragmentation in Bangladesh. J Environ Manage. 2021;280:111711. doi: 10.1016/j.jenvman.2020.111711 [DOI] [PubMed] [Google Scholar]
77.Vergílio M, Fonseca C, Calado H, Borges PAV, Elias RB, Gabriel R, et al. Assessing the efficiency of protected areas to represent biodiversity: a small island case study. Envir Conserv. 2016;43(4):337–49. doi: 10.1017/s037689291600014x [DOI] [Google Scholar]
78.Singh M, Griaud C, Collins CM. An evaluation of the effectiveness of protected areas in Thailand. Ecological Indicators. 2021;125:107536. doi: 10.1016/j.ecolind.2021.107536 [DOI] [Google Scholar]
79.Starnes T, Beresford AE, Buchanan GM, Lewis M, Hughes A, Gregory RD. The extent and effectiveness of protected areas in the UK. Global Ecology and Conservation. 2021;30:e01745. doi: 10.1016/j.gecco.2021.e01745 [DOI] [Google Scholar]
80.Caujapé-Castells J, Tye A, Crawford DJ, Santos-Guerra A, Sakai A, Beaver K, et al. Conservation of oceanic island floras: Present and future global challenges. Perspectives in Plant Ecology, Evolution and Systematics. 2010;12(2):107–29. doi: 10.1016/j.ppees.2009.10.001 [DOI] [Google Scholar]
81.Hortal J, Borges PAV, Jiménez-Valverde A, de Azevedo EB, Silva L. Assessing the areas under risk of invasion within islands through potential distribution modelling: The case of Pittosporum undulatum in São Miguel, Azores. Journal for Nature Conservation. 2010;18(4):247–57. doi: 10.1016/j.jnc.2009.11.002 [DOI] [Google Scholar]
82.Silva LB, Alves M, Elias RB, Silva L. Comparison ofT-Square, Point Centered Quarter, andN-Tree Sampling Methods inPittosporum undulatumInvaded Woodlands. International Journal of Forestry Research. 2017;2017:1–13. doi: 10.1155/2017/2818132 [DOI] [Google Scholar]
83.Heleno R, Lacerda I, Ramos JA, Memmott J. Evaluation of restoration effectiveness: community response to the removal of alien plants. Ecol Appl. 2010;20(5):1191–203. doi: 10.1890/09-1384.1 [DOI] [PubMed] [Google Scholar]
84.Heleno RH, Ramos JA, Memmott J. Integration of exotic seeds into an Azorean seed dispersal network. Biol Invasions. 2012;15(5):1143–54. doi: 10.1007/s10530-012-0357-z [DOI] [Google Scholar]
85.Borges PAV, Rigal F, Ros‐Prieto A, Cardoso P. Increase of insular exotic arthropod diversity is a fundamental dimension of the current biodiversity crisis. Insect Conserv Diversity. 2020;13(5):508–18. doi: 10.1111/icad.12431 [DOI] [Google Scholar]
86.Lhoumeau S, Tsafack N, Manso S, Figueiredo T, Leite A, Parmentier L, et al. Monitoring arthropods under the scope of the LIFE-BEETLES project: I - Baseline data with implementation of the Index of Biotic Integrity. Biodivers Data J. 2024;12:e124799. doi: 10.3897/BDJ.12.e124799 [DOI] [PMC free article] [PubMed] [Google Scholar]
87.Boieiro M, Matthews TJ, Rego C, Crespo L, Aguiar CAS, Cardoso P, et al. A comparative analysis of terrestrial arthropod assemblages from a relict forest unveils historical extinctions and colonization differences between two oceanic islands. PLoS One. 2018;13(4):e0195492. doi: 10.1371/journal.pone.0195492 [DOI] [PMC free article] [PubMed] [Google Scholar]
88.Borges Silva L, Lourenço P, Teixeira A, Azevedo EB, Alves M, Elias RB, et al. Biomass valorization in the management of woody plant invaders: The case of Pittosporum undulatum in the Azores. Biomass and Bioenergy. 2018;109:155–65. doi: 10.1016/j.biombioe.2017.12.025 [DOI] [Google Scholar]
89.Borges Silva L, Teixeira A, Alves M, Elias RB, Silva L. Tree age determination in the widespread woody plant invader Pittosporum undulatum. Forest Ecology and Management. 2017;400:457–67. doi: 10.1016/j.foreco.2017.06.027 [DOI] [Google Scholar]
90.Dutra Silva L, Brito de Azevedo E, Bento Elias R, Silva L. Species Distribution Modeling: Comparison of Fixed and Mixed Effects Models Using INLA. IJGI. 2017;6(12):391. doi: 10.3390/ijgi6120391 [DOI] [Google Scholar]
91.McGarigal K. FRAGSTATS: Spatial pattern analysis program for quantifying landscape structure. US Department of Agriculture, Forest Service, Pacific Northwest Research Station. 1995. [Google Scholar]
92.Lenk A, Richter R, Kretz L, Wirth C. Effects of canopy gaps on microclimate, soil biological activity and their relationship in a European mixed floodplain forest. Sci Total Environ. 2024;941:173572. doi: 10.1016/j.scitotenv.2024.173572 [DOI] [PubMed] [Google Scholar]
93.Richter T, Geres L, König S, Braziunas KH, Senf C, Thom D, et al. Effects of climate and forest development on habitat specialization and biodiversity in Central European mountain forests. Commun Biol. 2024;7(1):1518. doi: 10.1038/s42003-024-07239-6 [DOI] [PMC free article] [PubMed] [Google Scholar]
94.Santos F, Valente MA, Miranda PM, Aguiar A, Azevedo E, Tomé A. Climate change scenarios in the Azores and Madeira Islands. World Resource Review. 2004;16:473–91. [Google Scholar]
95.Ferreira MT, Cardoso P, Borges PAV, Gabriel R, de Azevedo EB, Reis F, et al. Effects of climate change on the distribution of indigenous species in oceanic islands (Azores). Climatic Change. 2016;138(3–4):603–15. doi: 10.1007/s10584-016-1754-6 [DOI] [Google Scholar]
96.Goodland T, Healey JR. The invasion of Jamaican montane rainforests by the Australian tree Pittosporum undulatum. School of Agricultural and Forest Sciences, University of Wales Bangor. 1996. [Google Scholar]
97.Bellingham PJ, Tanner EVJ, Martin PH, Healey JR, Burge OR. Endemic trees in a tropical biodiversity hotspot imperilled by an invasive tree. Biological Conservation. 2018;217:47–53. doi: 10.1016/j.biocon.2017.10.028 [DOI] [Google Scholar]
98.Bellingham PJ, Tanner EVJ, Healey JR. Hurricane disturbance accelerates invasion by the alien tree Pittosporum undulatum in Jamaican montane rain forests. J Vegetation Science. 2005;16(6):675–84. doi: 10.1111/j.1654-1103.2005.tb02410.x [DOI] [Google Scholar]
99.MacDougall AS, Gilbert B, Levine JM. Plant invasions and the niche. Journal of Ecology. 2009;97(4):609–15. doi: 10.1111/j.1365-2745.2009.01514.x [DOI] [Google Scholar]
100.Tsafack N, Lhoumeau S, Ros-Prieto A, Navarro L, Kocsis T, Manso S, et al. Arthropod-based biotic integrity indices: A novel tool for evaluating the ecological condition of native forests in the Azores archipelago. Ecological Indicators. 2023;154:110592. doi: 10.1016/j.ecolind.2023.110592 [DOI] [Google Scholar]
101.Belluau M, Paquette A, Gravel D, Reich PB, Stefanski A, Messier C. Exotics are more complementary over time in tree biodiversity–ecosystem functioning experiments. Functional Ecology. 2021;35(11):2550–61. doi: 10.1111/1365-2435.13900 [DOI] [Google Scholar]
102.Davies KF, Chesson P, Harrison S, Inouye BD, Melbourne BA, Rice KJ. SPATIAL HETEROGENEITY EXPLAINS THE SCALE DEPENDENCE OF THE NATIVE–EXOTIC DIVERSITY RELATIONSHIP. Ecology. 2005;86(6):1602–10. doi: 10.1890/04-1196 [DOI] [Google Scholar]
103.Borges PAV, Pimentel R, Carvalho R, Nunes R, Wallon S, Ros-Prieto A. Seasonal dynamics of arthropods in the humid native forests of Terceira Island (Azores). Arquipelago-Life and Marine Sciences. 2017;34:105–22. [Google Scholar]
104.Gaspar C, Gaston KJ, Borges PAV, Cardoso P. Selection of priority areas for arthropod conservation in the Azores archipelago. J Insect Conserv. 2010;15(5):671–84. doi: 10.1007/s10841-010-9365-4 [DOI] [Google Scholar]

PLoS One. 2025 Jun 16;20(6):e0326304. doi: 10.1371/journal.pone.0326304.r001

Author response to Decision Letter 0

26 Dec 2024

PLoS One. doi: 10.1371/journal.pone.0326304.r002

Decision Letter 0

Francesco Boscutti

13 Feb 2025

Dear Dr. Lhoumeau,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

I have received and had the opportunity to evaluate the reviews from three reviewers. While one reviewer appreciated the work conducted, the other two reviewers identified significant weaknesses in the methodological approach that must be addressed or clarified before proceeding with further evaluation.Therefore, I ask the authors to carefully consider the feedback provided by the reviewers when revising the manuscript, especially to clarify the most critical points.

Please submit your revised manuscript by Mar 30 2025 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org . When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'.
A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'.
An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'.

If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.

If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions see: https://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols . Additionally, PLOS ONE offers an option for publishing peer-reviewed Lab Protocol articles, which describe protocols hosted on protocols.io. Read more information on sharing protocols at https://plos.org/protocols?utm_medium=editorial-email&utm_source=authorletters&utm_campaign=protocols .

We look forward to receiving your revised manuscript.

Kind regards,

Francesco Boscutti

Academic Editor

PLOS ONE

Journal Requirements:

When submitting your revision, we need you to address these additional requirements.

1. Please ensure that your manuscript meets PLOS ONE's style requirements, including those for file naming. The PLOS ONE style templates can be found at

https://journals.plos.org/plosone/s/file?id=wjVg/PLOSOne_formatting_sample_main_body.pdf and

https://journals.plos.org/plosone/s/file?id=ba62/PLOSOne_formatting_sample_title_authors_affiliations.pdf

2. In your Methods section, please provide additional information regarding the permits you obtained for the work. Please ensure you have included the full name of the authority that approved the field site access and, if no permits were required, a brief statement explaining why.

3. Thank you for stating the following in the Acknowledgments Section of your manuscript:

“S.L. is funded by the Azorean Government Ph.D. grant numbers M3.1.a/F/012/2022. R.B.E, RG and P.A.V.B. are currently funded by the projects Azores DRCT Pluriannual Funding (M1.1.A/INFRAEST CIENT/001/2022) and FCT—Fundação para a Ciência e Tecnologia FCT[1]UIDB/00329/2020-2024 DOI 10.54499/UIDB/00329/2020 (Thematic Line 1—integrated ecological assessment of environmental change on biodiversity). D.S received no outside funding.”

We note that you have provided funding information that is not currently declared in your Funding Statement. However, funding information should not appear in the Acknowledgments section or other areas of your manuscript. We will only publish funding information present in the Funding Statement section of the online submission form.

Please remove any funding-related text from the manuscript and let us know how you would like to update your Funding Statement. Currently, your Funding Statement reads as follows:

“S.L. is funded by the Azorean Government Ph.D. grant numbers M3.1.a/F/012/2022.

R.B.E, RG and P.A.V.B. are currently funded by the projects Azores DRCT Pluriannual Funding (M1.1.A/INFRAEST CIENT/001/2022) and FCT—Fundação para a Ciência e Tecnologia FCT-UIDB/00329/2020-2024 DOI 10.54499/UIDB/00329/2020 (Thematic Line 1—integrated ecological assessment of environmental change on biodiversity).

D.S received no outside funding.”

Please include your amended statements within your cover letter; we will change the online submission form on your behalf.

4. Thank you for stating the following financial disclosure:

“S.L. is funded by the Azorean Government Ph.D. grant numbers M3.1.a/F/012/2022.

D.S received no outside funding. “

Please state what role the funders took in the study. If the funders had no role, please state: "The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript."

If this statement is not correct you must amend it as needed.

Please include this amended Role of Funder statement in your cover letter; we will change the online submission form on your behalf.

5. In the online submission form, you indicated that “Data are available on request.”

All PLOS journals now require all data underlying the findings described in their manuscript to be freely available to other researchers, either 1. In a public repository, 2. Within the manuscript itself, or 3. Uploaded as supplementary information.

This policy applies to all data except where public deposition would breach compliance with the protocol approved by your research ethics board. If your data cannot be made publicly available for ethical or legal reasons (e.g., public availability would compromise patient privacy), please explain your reasons on resubmission and your exemption request will be escalated for approval.

[Note: HTML markup is below. Please do not edit.]

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

Reviewer #1: Yes

Reviewer #2: No

Reviewer #3: Partly

**********

2. Has the statistical analysis been performed appropriately and rigorously? -->?>

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

**********

3. Have the authors made all data underlying the findings in their manuscript fully available??>

The PLOS Data policy

Reviewer #1: No

Reviewer #2: No

Reviewer #3: Yes

**********

4. Is the manuscript presented in an intelligible fashion and written in standard English??>

Reviewer #1: Yes

Reviewer #2: No

Reviewer #3: No

**********

Reviewer #1: The manuscript PONE-D-24-59937 (“Landscape to Microhabitat: Uncovering the Multiscale Complexity of Azorean Forests”) identify the structural and compositional differences between native and exotic woodlands on Terceira Island, Azores.

The manuscript is correct and it is good. The references is very good and the history very well explained and its justification. The work is very interesting.

The introduction and methodology is correct but it’s necessary some annotations (see below). With respect to the results, I see it as good, although is necessary basic information. Finally, in the discussion section, it was very well written.

Some annotations:

With respect to material and methods, the plots area (20 x 20 m) are enough? What determines the size of the plot? The maximum height of the trees?

The authors could considered include table 1 as supplementary material.

Figure 3 needs improvement.

It would be interesting for the authors to include a list of the species present in each plot and in each treatment (native and exotic woodlands) as supplementary material indicating, if possible, their origin species (native, endemic, introduced, invasive).

In addition, it would be good to include a short introduction to the results with a paragraph with the percentages of species present in each type of forest.

In the discussion, the authors indicates that were ten plot in native woodlands but really are nine (Second paragraph in “The characterization of landscapes is a consequence of human accessibility and land-use”)

Reviewer #2: Abstract … By analysing landscape, habitat, and microhabitat traits, we found that native forests are situated in less accessible terrains…. rephrase, the location of native forests is not a trait, or derived from the fact that they are native, just the opposite, they are the remains of a former native forest covering all the locations.

Abstract … homogeneous structural complexity derived from endemic vascular plant species…. I do not agree with "derived", it should be "and", adding enough exotic species or letting succession into the non-native forest will eventually result in complexity, complexity does not derive from endemicity (see comments on the Results).

Abstract ...exotic forests, which are situated in human-modified landscapes; Exotic woodlands are the human modified landscape, rephrase as "exotic forests, are the result of human actions, afforestation or introduction of invading tree plants.

Abstract ...The ground and canopy layers in exotic forests were more invaded by nonindigenous species, while the understory demonstrated greater resilience... very confusing statement, first an absolute need to resolve the difference between afforested areas and invaded areas, then also to differential use and actions of both, usually afforested areas have periodical cleaning of the understory?

Abstract ...Our findings suggest a temporal progression of forest change, from pristine native to disturbed exotic stands.; The authors have no follow up of the dynamics of the forest to support this statement, by contrary many references exist proving the Azores forest cover suffered a massive and historical change, the object of study are the results of the change, conclusions cannot be to prove the chosen model of exotic versus native exists, something that should be stated in the abstract as historical, but by contrary to explain the complexity, diversity etc of the 2 distinct “woodlands”

Abstract “...These insights highlight the necessity for scale-specific conservation, prioritising native forests in remote areas and controlling invasive species in exotic forests to enhance ecological resilience”; basically what the authors propose is to protect what already is protected not because is legally protected but because is as stated "in less accessible terrains" and to keep the exotic areas as exotic although this exotic are themselves invasive, this is an absurd

Introduction The structure of the introduction is inverted, the object of study should firstly be defined and then the first 3 paragraphs on the first page should follow.

Introduction The Azores, one of the most remote archipelagos in the North Atlantic Ocean, is made up of nine islands where forests contain a mix of native and exotic species, shaped by both natural processes and six centuries of human influence. (Elias et al. 2016). This or a modified version of this sentence should be the opening sentence of the Introduction, the phrase is however overly optimistic in the use of the concept of "Mosaic" or “Mix”, the Azores have certainly less than 5% of Native forest cover and therefore a Mosaic of 5% versus 95% is not a mosaic. This needs to be clearly expressed by the authors on the introduction. Several studies published by one of the authors (Elias) can be used to state and support this key point to the readers.

Introduction ...consist primarily of broad-leaved evergreen trees. There are according to Elias (2016), Dias et al. (2021), and others several types of vegetation including some that are not broad-lead. To characterize the broad-leaved evergreen trees as such without any further hint or name is insufficient; include also the references: Dias, Eduardo; Mendes, Cândida; Aguiar, Carlos (2021). Vegetação dos Açores. In Capelo, J.; Aguiar, C. (Eds.), Vegetação de Portugal. Lisboa: INCM, p. 155-179. ISBN 978-972-27-2879-9; Mucina, L.; Bültmann, H.; Dierßen, K.; Theurillat, J.-P.; Raus, T.; Carni, A.; Šumberová, K.; et al. "Vegetation of Europe: hierarchical floristic classification system of vascular plant, bryophyte, lichen, and algal communities". Applied Vegetation Science 19 (2016): 3-264; Fernández Prieto, J.C.; Aguiar, C.; Dias, E.; Fernández Prieto, J.A.; Aguiar, Carlos; Dias, Eduardo; FernÃ¡ndez Prieto, JosÃ© Antonio. "Description of some new syntaxa from the Azores archipelago". International Journal of Geobotanical Research 2 1 (2012): 111-116. http://dx.doi.org/10.5616/ijgr120007

Introduction ...many endemic taxa Characterize "Many", or compare with other similar forests, however we lack the sense/definition of forest and therefore a way to compare with other similar forests. There is reference in this introduction characterizing the types of forest and giving proper biogeographical framework.

Introduction ...As a result, the Azores’s landscape is now a mosaic of native and exotic forests, each playing a different ecological role… This is a bold statement and a conclusion, furthermore without references, see above the comment on the "Mosaic", do invading exotic plants play a role is this a political or a scientific statement?

Introduction ...Native forests are crucial for maintaining the Azorean island’s biodiversity, acting as refuges for endemic plants and animals (Lhoumeau and Borges 2023) Well… native forests are native in fact.

Introduction Finally, the vegetation data collected from surveys provides information on species composition and density across all layers. The data, gathered on Terceira Island, are used to address the following question: What are the defining characteristics of the vegetation structure of the various types of Azorean forests, with a particular focus on the native and exotic woodlands? By answering this question, this study aims to provide a detailed characterisation of Terceira's forests, offering insights into how both native and exotic forest types are integrated within the island's broader ecosystem. The reader finds out that after all the study concerns one island out of nine islands, that needs to be addressed on the proposed title "Landscape to Microhabitat: Uncovering the Multiscale Complexity of Terceira Island forests (Azores, Portugal)" but see further comments below.

Material and Methods. Study Area and Site selection The second part of the first paragraph needs to be moved to the introduction (to a new and so far lacking characterization of the Terceira forests and habitats)

Material and Methods. Study Area and Site selection The sentence "the third largest of the nine islands in the archipelago (figure 1)." should be moved to the first paragraph

Material and Methods. Study Area and Site selection The sentence "which are characterised by broadleaved evergreen trees and are home to a variety of endemic plant species" is conclusive and derives from the results themselves should deleted.

Material and Methods. Study Area and Site selection What is meant by "by exotic vegetation, primarily consisting of Pittosporum undulatum", Pittosporum undulatum is an invasive plant species very well known, documented etc. therefore 1) there should be detailed information on this species on the introduction, including reference to many publications concerning the Azores/Pittosporum undulatum question; 2) Pittosporum undulatum is an Invasive tree species and should be delt as invasive; 3) if there are no other dominant exotic species referred on the study (such as Cryptomeria japonica, the dominant exotic tree in the Azores... then the title of the manuscript should be further adapted/changed to fit this much more simple comparison. One Island and Native (even this can be explicit) versus Pittosporum invaded areas.

Material and Methods. Study Area and Site selection There is a lacking explanation on the 18 plots choice, it cannot just be because they are already in use in something else. Are they bioclimaticaly homogeneous? Are they similar in use, in historical use? Etc. A table with all the plots and as many characteristics as possible should be included, namely altitude, slope, topographic complexity, bioclimate, rainfall etc.......And an explanation on the choice of course.

Material and Methods. Study Area and Site selection What is meant by "Native vegetation" there can be native grasslands, native scrub, native bogs, native….. It does not mean native forest, the reader can be led to think that the "Native vegetation" on Figure 1, is the same as the Native forest on Figure 2, no true!

Material and Methods. Study Area and Site selection Why include here Figure 2? It looks like a result; in any case it should be moved and the plots clearly identified (meaning that the images on Figure 2 should correspond to 2 of the studied plots)

Material and Methods. Vegetation Survey The exotic forest plots were surveyed in the spring of 2023 within 20 x 20 meter plots, while the native forest plots were surveyed earlier, during the summer of 2012 and 2013, within larger 50 x 50 meter plots. This seems to be an insurmountable methodological problem with a very complex (impossible?) solution, a 10 year difference in the survey! Thats a decade, plants/trees do grow in 10 years. How can this be addressed when considering that other data such as "UAV canopy mapping" and "Terrestrial laser scanning" do not match the inventories? Even more taken into account that the authors state below that forests are homogeneous, were they 10 years ago? and then why should they still be homogeneous or even keep the same composition 10 years later?

Material and Methods. Vegetation Survey These surveys were designed following a standardised protocol (Borges et al. 2018). The protocol needs to be here described, but how can a protocol be applied in 2012 if it was published in 2018?

Material and Methods. Vegetation Survey The objective was to obtain comprehensive data on the composition of forest species. Eventually this statement should precede everything else.

Material and Methods. Vegetation Survey Due to the relative homogeneity of the native forests, no rarefaction process was applied to the data from these plots, allowing for the retention of all inventory data. This decision reflects the low variability in species composition within the native forest, ensuring a more accurate and robust comparison with exotic forest plots. This needs to be clearly explained, in any case it should belong to another part of the M & M, maybe data treatment? As it is corresponds to an empty sentence

Material and Methods. Vegetation Survey Species richness (H₀), representing the total number of species present in each plot, was recorded to evaluate biodiversity within the forest plots Therefore according to the authors species richness and biodiversity are the same concept? Does biodiversity increase with alien species? Is this a scientific statement or a political concession for managers of the Azorean landscape?

Material and Methods. Vegetation Survey Additionally, the basal area of trees with a diameter at breast height (DBH) greater than 10 cm was calculated in hectares. This variable provides an estimate of tree density and size, which is crucial for understanding forest biomass and its contribution to the overall structure of the forest. This sentence needs to be rewritten; the meaning is unclear.

Material and Methods. Vegetation Survey Another important metric, species density, was quantified by counting the number of shoots per species and per square meter, allowing for an assessment of vegetation density in different areas. More information about the protocol can be found in (Borges et al. 2018). Again at least partially the protocol should be detailed here, it was published in 2018 but the "native forest" plots surveyed 6 years before. This is confusing and not acceptable.

Material and Methods. Vegetation Survey These measurements were further classified in three distinct forest strata: the ground layer, the understory, and the canopy, offering a vertical profile of the forest structure. Furthermore, species were categorized into four groups—endemic, native, introduced, and invasive—resulting in a total of twelve variables, with each stratum and species category providing specific insights into the forest’s ecological composition and structure. I cannot understand this sentence, was DBH measured on the understory plants? How was density measured at the ground layer, just trees? Based on what did the authors segregate "introduced" and "invasive", a published list based on Azorean flora crossed with concepts like those published by Pyšek, Richardson and many others?

Material and Methods. Sites and lanscape characteristics For each of the 18 study sites on Terceira Island, detailed data on elevation and landscape characteristics were collected to better understand the environmental factors influencing forest structure. If the sites are not homogeneous in what concerns elevation and other geographical/ecological factors then how can they be compared?

Material and Methods. Sites and lanscape characteristics Furthermore, landscape heterogeneity was quantified in the surrounding area of each site. Land use data, obtained from the Azorean government, were processed and analysed in QGIS. A quadrat of side 500 meters was designed around all plots, and the proportion of land use was assessed per category. Data of the "Azorean government" should be of free access if so give an url on the text. This data are recent? Why not using the UAV to obtain the data? Is the classification of the "Azorean government" a clear match to the authors needs? See above the comment on Native vegetation and Native forest.

Material and Methods. Sites and landscape characteristics Table 1 might deserve a detailed comment, there are no invasive species on the ground layer

Material and Methods. Sites and landscape characteristics Table 1. Finally the reader understands that although there are references to arthropods and other types of non-plant diversity, this is a study of plant diversity, there are no other assessments being introduced on this manuscript. This a study of plants without reference to the actual plants, even less types of plant communities, very peculiar.

Material and Methods. Sites and landscape characteristics In fact what the authors seem to have studied are one peculiar type of native Forest (broad leaved although in the discussion Juniperus brevifolia is mentioned as dominant and this is not a broad leaf plant) and one type of exotic/invaded Forest (a Pittosporum dominated area, calling it forest another misleading concept)

Results The characterisation of landscapes is a consequence of human accessibility and land-use; this is what the authors decided to study not a conclusion of their study, in any case there no references to historical use of the Azorean forests on the introduction, a major issue since it clearly determines the framework of the study.

Results The structural complexity of forest stands is derived from different sources in native and exotic woodlands; what the authors are trying to say is that distinct “Natural” “successional” routes are being observed in distinct “forest”, obviously they are different, they are historically distinct, the easily accessed areas had since the XV century many distinct uses, please read historical papers! They were initially cut for wood, them burned and cultivated for wheat then…… plants with Pittosporum and invaded by Pittosporum (and many other exotic plants), therefore the sources are human (potentially infinite, where are invading plants coming from, how many a year/decade?) or based on the few refugia (a concept not explored on the text). Further more what the authors refer as native (without description detail etc.) are mature forests? Secondary forests on permanent ecological/successional stands derived from there “complex orography”, were they cut in the past (certainly they were although possibly not cultivated)

Results The intrinsic complexity of native stands may be attributed to the traits of the few endemic tree species (e.g. the Azorean endemic cedar Juniperus brevifolia), which exhibit greater branch ramifications, OR they can attributed to the fact that they or not the ecological equivalent of the Pittosporum stands, in order to solve this comundrum Native forests in areas not corresponding to refugia should be included, it might even occur that the dominant species in smooth areas to be distinct species.

Results The canopy of native forests shows greater structural and compositional homogeneity If they represent simplified versions of the Native Forest due to historical use and refugia position this is exactly what we all expect to happen.

Statistical complexity does not solve the problems found in the original data, to the end of the manuscript the biological descriptors are unclear, vascular plants? Vascular and Bryophytes? Arthropods?

Reviewer #3: Dear authors

After throughout analysis of the manuscript (MS), my general opinion is that the research question is interesting, but, despite analytical workflow being adequate, there are some flaws that may compromise the coherence of the MS. Also, the results are somewhat self-evident, for instance that natural/pristine forest is structurally more complex than artificial/exotic forest stands. Besides I would expect that some possible analysis of functional diversity between the two types of forest as the result of different history and drivers could have been addressed by author.

In concrete, I may point some of the flaws or aspects that are unclear I think should be addressed in a futures version of the MS.

1. The sample is too small to be representative. I understand that logistic effort might restrain the dimension of the sample buu, 18 plots hardly represent the ecological variability of the Azorean Forest.

2. It is very unclear the exact dates of sampling, because authors state that sampling has started in 2012’ and could mean that 13 plots were sampled at that time or thenceforth (when exactly?). Some sampling was made already in the summer of 2024. Therefore, part of the (already small) sample was made with an interval of maybe 12 years. This means that ecological succession may have led to composition and structure changes and some soil use change could have happened. I think you cannot compare plots with such a time span without accounting for time, which authors did not in their analysis.

Another unclear aspect is the discrepancy of dates of the survey of metrics: the method reference (Borges, 2018) is posterior to the putative dates of the survey (2012, 2013). I really have a difficulty with understanding what procedure was really used at the time.

3. The detailed technical description of devices and procedure of canopy survey by LIDAR is superfluous and cumbersome in the main text and should be either omitted or sent to supplementary materials.

4. I would like to see in a table how the parameters sampled in the surveys were converted to concrete trait variables and their scale values. The table presenting the 49 variables dos does not do this.

5. The sampling of plant species simply classified into ‘native’ and ‘exotic/invasive’ is a very poor floristic classification of plant species. I think it is hard to understand and overly simplistic.

6. The use of arbitrary surface for plots for the sake of homogeneity, not using minimal-area/rarefaction procedure is unjustified. Rarefaction can be used once for each forest type then the surface value used repeatedly.

7. The idea of indirect ordination by NMDS and then analysing driver correlates by Spearman correlation with axes is a good idea, although there are direct methods (canonical correlation or canonical correspondence analysis) that might have bee used instead. The real problem – I have serious difficulties in understanding – is that authors seem to have performed the analysis on a matrix with all the variables (!?). And then candidate explanatory variables were re-used (with Spearman correlation) to interpret NMDS axis? The procedure is not clear in the MS.

8. Please explain what is the ‘R statistic’. Is it Spearman correlation coefficient?

9. The procedure leading to variable groups is unclear. Whas it arbitrary/subjective?

10. Discussion is very elaborate and dissects each the main results. But, most of it does not derive from the MS results, so being arbitrary many times, as for instance, comments of flora diversity – when no flora was sampled, just ‘native/exotic’. S0, the discussion is absolutely exaggerated in its extension and mostly based on literature no the author´s own results. If not somewhat speculative or free-floating (not supported neither by results or literature).

Another example of irrelevance is the whole discussion of several-scale analysis, from micro-habitat to stand scale. Nothing in the sampling procedure separates different spatial scales. I recommend that, in future versions of MS, the discussion to be much shorter and sticking to discussion of results and only comparisons with relevant similar results or needed to interpretation. Otherwise, suddenly readers get a new review article inside the MS.

I should remind that results are, in great extent, very trivial ones.

Therefore, I recommend Major Revision of the MS.

Best regards.

A reviewer.

**********

what does this mean? ). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy

Reviewer #1: No

Reviewer #2: No

Reviewer #3: No

**********

[NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.]

While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/ . PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org . Please note that Supporting Information files do not need this step.

Attachment

Submitted filename: Comments on PONE_D_24_59937_Landscape to Microhabitat.pdf

pone.0326304.s002.pdf^{(477.3KB, pdf)}

PLoS One. 2025 Jun 16;20(6):e0326304. doi: 10.1371/journal.pone.0326304.r003

Author response to Decision Letter 1

14 Mar 2025

Journal Requirements:

When submitting your revision, we need you to address these additional requirements.

1. Please ensure that your manuscript meets PLOS ONE's style requirements, including those for file naming. The PLOS ONE style templates can be found at

https://journals.plos.org/plosone/s/file?id=wjVg/PLOSOne_formatting_sample_main_body.pdf

and

https://journals.plos.org/plosone/s/file?id=ba62/PLOSOne_formatting_sample_title_authors_affiliations.pdf

We have formatted the manuscript according to the guidelines provided in the PLOS ONE style templates, including the file naming conventions.

We have added the requested information regarding the permits in the Methods section.

3. Thank you for stating the following in the Acknowledgments Section of your manuscript:

Please remove any funding-related text from the manuscript and let us know how you would like to update your Funding Statement. Currently, your Funding Statement reads as follows:

“S.L. is funded by the Azorean Government Ph.D. grant numbers M3.1.a/F/012/2022.

D.S received no outside funding.”

Please include your amended statements within your cover letter; we will change the online submission form on your behalf.

We corrected the manuscript accordingly. The Funding Statement you provided is correct.

4. Thank you for stating the following financial disclosure:

“S.L. is funded by the Azorean Government Ph.D. grant numbers M3.1.a/F/012/2022.

D.S received no outside funding. “

If this statement is not correct you must amend it as needed.

Please include this amended Role of Funder statement in your cover letter; we will change the online submission form on your behalf.

We added the statement that our funders did not have any role in the Funding Statement.

5. In the online submission form, you indicated that “Data are available on request.”

We have addressed the data availability requirements by adding all data used in the manuscript as supplementary materials.

Review Comments to the Author

Reviewer #1:

The manuscript PONE-D-24-59937 (“Landscape to Microhabitat: Uncovering the Multiscale Complexity of Azorean Forests”) identify the structural and compositional differences between native and exotic woodlands on Terceira Island, Azores.

The manuscript is correct and it is good. The references is very good and the history very well explained and its justification. The work is very interesting.

Some annotations:

With respect to material and methods, the plots area (20 x 20 m) are enough? What determines the size of the plot? The maximum height of the trees?

Thank you for your positive feedback on our manuscript. Regarding the plot size in the Materials and Methods section, the 20 x 20 m plots were determined based on accessibility and logistical considerations. Due to the small stature of Azorean forests, plots sizes usually range from 5x5 m to 15 x 15 m (e.g. Dias et al. 2011; Elias et al. 2011; Elias et al. 2016. Additionally, the empirical assessment of the homogeneity of the surroundings at the center of the plot justified the selection of this plot size.

The authors could considered include table 1 as supplementary material.

Figure 3 needs improvement.

Thank you for your suggestions. We have moved Table 1 to the supplementary material and added this mention in the beginning of the paragraph. Additionally, we have improved the visual quality of Figure 3 and incorporated some critical information from the former Table 1 into the figure for better clarity. Please note that figure 3 become figure 2 as the former figure 2 was moved to the results based on the comment of the second referee.

Following the editor's guidelines, we have now provided all the data used in the analysis as supplementary materials. This includes a list of the species present in each plot and treatment (native and exotic woodlands), along with their colonization origin based on the updated information available in AZORESBIOPORTAL (native non-endemic, endemic, introduced, invasive).

In addition, it would be good to include a short introduction to the results with a paragraph with the percentages of species present in each type of forest.

We have added brief descriptive sentences at the beginning of the Results section as well as a table summarising our surveys.

Thank you for pointing out the discrepancy. We have corrected the typo in the discussion section. Initially, ten plots were selected, but one plot was removed from the study due to the inability to obtain LiDAR data for it, resulting in a total of nine plots in the native woodlands.

Reviewer #2:

Abstract … By analysing landscape, habitat, and microhabitat traits, we found that native forests are situated in less accessible terrains…. rephrase, the location of native forests is not a trait, or derived from the fact that they are native, just the opposite, they are the remains of a former native forest covering all the locations.

We have revised the abstract to clarify that the current locations of native forests in less accessible terrains are not inherent traits of these forests.

What we meant was that endemic trees, such as the dominant Juniperus brevifolia, exhibit a branching architecture that directly contributes to the structural complexity observed in native forests. To clarify this point, we have revised the text accordingly.

Thank you for your suggestion. The plots are in sites where there was afforestation followed by agricultural use that was latter abandoned, allowing the invasion of exotic tree species. We have rephrased the sentence to clarify that exotic forests result from human actions, including afforestation or the introduction of invasive tree species.

We acknowledge the importance of distinguishing between afforested and invaded areas. Based on our knowledge, nearly all exotic forest plots in this study were originally afforested for orchards or vineyards and later abandoned. Currently, there is no evidence of ongoing human intervention in these areas or their surroundings. However, we recognize the limitation that precise historical land-use data are not available. We also have clarified the point in the manuscript that the understory layer considered in this study is richer in terms of native species comparing to the ground and canopy layers.

We agree and have rephrased the statement to remain more factual, emphasizing the historical context of forest change in the Azores and focusing on the structural and ecological characteristics of the two distinct woodland types.

We acknowledge the need to clarify our statement and have rephrased it to emphasize the importance of concrete conservation actions and continuous monitoring. While protected areas may be designated, their effective management and enforcement are essential to preserving native forests and controlling invasive species in exotic woodlands. In fact, we still see many areas in the archipelago (eg. In Flores, São Jorge and Faial) where the protection is only in the paper. Cattle is still moving around freely. This revision ensures a more action-oriented perspective in our conclusions.

Introduction The structure of the introduction is inverted, the object of study should firstly be defined and then the first 3 paragraphs on the first page should follow.

Thank you for your suggestion. However, we have chosen to maintain the current structure of the introduction, as it follows a standard scientific writing approach—first presenting the broader context of the study before defining its specific objectives. We believe this approach enhances the clarity of the narrative, providing a coherent and logical progression of ideas that guides the reader from general background information to the precise aims of the research.

We have rephrased "mosaic" to "patches" to more accurately reflect the limited extent of native forest cover in the Azores. Additionally, we have clarified this point in the introduction, citing relevant studies, to ensure readers understand the significant imbalance between native and exotic forest areas.

We agree that a more detailed characterization of the broad-leaved evergreen trees in the Azores is important. We have included peer-reviewed relevant references to clarify the diversity of native vegetation types in the archipelago. Additionally, we have provided a clear definition of the native woodlands considered in this study, which aims to provide a broad overview of the structural complexity of the main woodlands and their potential determinants.

We cited several references that detail the endemic species composition, including recent and updated checklists. To address your comment, we have now included a clear definition of the native vegetation type considered in this study in the Materials and Methods secti

Attachment

Submitted filename: Reviews comments V1_resubmission.docx

pone.0326304.s004.docx^{(45.1KB, docx)}

PLoS One. doi: 10.1371/journal.pone.0326304.r004

Decision Letter 1

Francesco Boscutti

12 Apr 2025

Dear Dr. Lhoumeau,

Please submit your revised manuscript by May 27 2025 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org . When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'.
A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'.
An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'.

We look forward to receiving your revised manuscript.

Kind regards,

Francesco Boscutti

Academic Editor

PLOS ONE

Journal Requirements:

Please review your reference list to ensure that it is complete and correct. If you have cited papers that have been retracted, please include the rationale for doing so in the manuscript text, or remove these references and replace them with relevant current references. Any changes to the reference list should be mentioned in the rebuttal letter that accompanies your revised manuscript. If you need to cite a retracted article, indicate the article’s retracted status in the References list and also include a citation and full reference for the retraction notice.

[Note: HTML markup is below. Please do not edit.]

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

Reviewer #1: All comments have been addressed

Reviewer #2: (No Response)

Reviewer #3: All comments have been addressed

**********

2. Is the manuscript technically sound, and do the data support the conclusions??>

Reviewer #1: Yes

Reviewer #2: Partly

Reviewer #3: Yes

**********

3. Has the statistical analysis been performed appropriately and rigorously? -->?>

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

**********

4. Have the authors made all data underlying the findings in their manuscript fully available??>

The PLOS Data policy

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English??>

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: (No Response)

**********

Reviewer #1: The work is very interesting and has improved a lot with respect to the previous version. All the changes proposed by the authors of this paper have been done correctly and those who have not agreed, the authors have justified it very well.

Reviewer #2: I keep my comment on the title: The reader finds out that after all the study concerns one island out of nine islands, that needs to be addressed on the proposed title "Landscape to Microhabitat: Uncovering the Multiscale Complexity of Terceira Island forests (Azores, Portugal)". The authors have no data on the Azores just for 1/9 of the islands.

Abstract

By analysing landscape(…) we found that less accessible terrains are covered by the remnants of native forests. (…) plant species.

The authors are again stating that “they found” instead rephrase as:

The authors state: However, we recognize the limitation that precise historical land-use data are not available.

In fact historical data on the Azores do exist, it’s not of course digital cartography from the XV/XVI centuries but several descriptions, or recent publications that synthetise these ancient documents (see e.g. Dias, on the book: Açores e Madeira - A Floresta das Ilhas. Pp. 255-296. Público, Comunicação Social SA, Fundação Luso Americana para o Desenvolvimento e Liga para a Protecção da Natureza. ISBN: 978-989-619-103-0)

Abstract

Comment by the authors: While protected areas may be designated, their effective management and enforcement are essential to preserving native forests and controlling invasive species in exotic woodlands. In fact, we still see many areas in the archipelago (eg. In Flores, São Jorge and Faial) where the protection is only in the paper. Cattle is still moving around freely.

Reply: I understand the comment and the commitment but there cannot be implicit conclusions in a paper, or the results show what the authors state on the comment or my comments, based solely on the authors data, are still pertinent. (see final remark)

The statement “These insights emphasize (…) the preservation of native forests and the control of invasive species in exotic woodlands.” Is therefore hard to accept as it is, the authors data are not on the management, or protected versus unprotected areas, from the authors data these conclusions cannot be drawn.

Introduction

The authors state:

However human activity significantly altered, with large areas being replaced by exotic species such as Cryptomeria japonica (L. f.) D.Don, 1841 and Pittosporum undulatum Vent., introduced for commercial forestry [29]. As a result, the Azores’s landscape has several patches of native and exotic woodlands in a matrix of agricultural fields [32,36], each with a different ecological importance. Native vegetation are crucial for maintaining the Azorean island’s biodiversity, acting as refuges for endemic plants and animals [37].

Delete “1841”

Later in the comments the authors refer to 33 % for Pittosporum, 31 for % Cryptomeria, since both pastures, vineyards and many other human uses of the landscape are still missing I guess that “significantly altered” means close to extinction? The authors need here to introduce values/numbers on the % of native vegetation remains and native forest (and cite the sources).

Introduction ...consist primarily of broad-leaved evergreen trees. There are according to Elias (2016), Dias et al. (2021), and others several types of vegetation including some that are not broad-lead. To characterize the broad-leaved evergreen trees as such without any further hint or name is insufficient; include also the references: Dias, et al (2021). Vegetação dos Açores. In Capelo, J.; Aguiar, C. (Eds.), Vegetação de Portugal. Lisboa: INCM, p; Mucina, et al. "Vegetation of Europe: hierarchical floristic classification system of vascular plant, bryophyte, lichen, and algal communities". Applied Vegetation Science 19 (2016): 3-264; Fernández Prieto, et al. "Description of some new syntaxa from the Azores archipelago". International Journal of Geobotanical Research 2 1 (2012): 111-116. http://dx.doi.org/10.5616/ijgr120007

The references included in my first review need to be included, there can be no cancellation on authors views or scientific approaches to vegetation study.

The authors state: “each with a different ecological importance” this is unacceptable for island vegetation/plant diversity since none of the human introduced uses is ecological important, all being ecological destructive. The statement says a lot on authors views on conservation. It needs to be deleted.

Introduction

Although the authors revised the use of “mosaic” this part of the introduction still needs to be improved using numerical data on types of cover.

Material and Methods.

1st paragraph

“…vegetation which were dominated” rephrase as “vegetation which are dominated”

What’s the meaning of “primarily consisting” means that are sites not dominated by Pittosporum?

Vegetation survey

“The objective was to obtain comprehensive data on the composition of forest species.” Rephrase objectives do not fit M&M

Material and Methods.

Cryptomeria is not the dominate exotic species. Pittosporum dominated areas occupy 33% of forest surface in the Azores. Production forests (mostly, but not only (!), of Cryptomeria) occupy 31%. This is according to the «State of the Environment Report of 2023» (Azorean Regional Government).

I accept that a further change on the title (apart from the geographical restriction) is not need, but use this data (numerical data) where required (see comment above)

Material and Methods. Study Area and Site selection

The authors in their reply refer to a table, I could not find the reference in the text.

Material and Methods.

Although the authors have improved the text concerning plots and time, both the difference in size and the 10 years difference need to be included in the discussion.

Original comment: Even more taken into account that the authors state below that forests are homogeneous, were they 10 years ago? and then why should they still be homogeneous or even keep the same composition 10 years later?

I agree that the authors have the needed information, the question is where do readers get that information? And there is no reference to that in the text, it needs to be included with references preferably published in peer-reviewed publications (as stated above by the authors)

The authors further reply: Conducting new surveys could risk altering the forest structure due to trampling, which is particularly important since the focus of this study is on the structural complexity of the forests.

This seems to be a very poor, and not included, explanation.

The authors further reply: Similarly, (…) we believe the 10-year difference does not undermine this objective.

In my view this weakness on the methodological approach cannot be solved just by answering to the reviewers using private and unpublished information.

The authors have two choices to publish the information in the paper or to cite another source.

Material and Methods. Vegetation Survey

Original comment: The exotic forest plots were surveyed in the spring of 2023 within 20 x 20 (…). Why are the plots different in size?

Reply by the authors: The larger 50 x 50 meter plots for the native forests were chosen during the design of the ISLANDBIODIV project and we use the data gathered. The 20 x 20 meter plots in the exotic forests were selected based on forest height, accessibility and logistical considerations. Furthermore, the homogeneity of the plots supported the selection of this area to represent the forest structure being studied.

Homogeneity is a type of data, not shown in the paper, just assumed in the reply, if the authors can show or produce evidence of this then the reply should be transferred into the text. Otherwise, its complex to accept.

Material and Methods. Vegetation Survey

Original comment: The protocol needs to be here described, but how can a protocol be applied in 2012 if it was published in 2018?

Authors reply: (…). The vegetation survey protocol was initially designed during earlier projects, notably ISLANDBIODIV and MOVECLIM, and was implemented in 2012 (…), leading to a delay in its official release.

I still don’t see the reply to “The protocol needs to be here described”

So, the readers are still missing a crucial point on methods used, describe the protocol even if just in a shorten version, was it adapted in any of its parts?

Material and Methods. Vegetation Survey

Original comment: Based on what did the authors segregate "introduced" and "invasive", a published list based on Azorean flora crossed with concepts like those published by Pyšek, Richardson and many others?

Authors reply: (…) The classification of species into "endemic," "native," "introduced," and "invasive" is based on Borges PAV, Costa A, (…). Principia, Parede. It compiles data from various sources and more recent updates available in AZORES BIOPORTAL

However, the original 2010 publication, for plants does not refer to naturalized versus invasive, just “Natu”, naturalized, please clarify this point, i.e. the distinction between introduced and invasive.

Further comments:

On the results the authors state: “high level of pristine composition when considering the endemic tree species.”

This sentence seems to contradict the absence of data on pristine forests (see above), in fact it implies that there is a model of pristine vegetation, is there?

Discussion

Is lacking a thorough discussion of possible drawbacks of methodological problems and adaptations, and in my view is clearly over-extended.

1st paragraph: “Furthermore, (…) invasion patterns” it seems a circular though/statement, if invaded i.e. Pittosporum dominated sites have a distinct structure then structure is an indicator of the dominance of Pittosporum….why should anyone use structure if the “indicator” is at plain sight?

1st Paragraph “The findings of this study highlight the necessity of examining forest structure at various spatial scales, as the differentiation between native and exotic forests exhibited significant variation depending on the spatial level under consideration.”

Consider discussing your results on a multi-invasion process, i.e. where Pittosporum is the dominant invading phanerophyte but other invading plants at distinct forest strata are also paving their way into the landscape.

2nd Paragraph: “concerning for the delicate ecosystem of the Azores” well very threatened, reduced, relictual?

4th Paragraph: “human presence on Terceira Island has led to the intentional and unintentional introduction of non-native species, particularly in forests accessible for resource extraction and agriculture.” If this this is a discussion, please insert a citation for this statement.

5th Paragraph: “The enhanced accessibility (...) replacement of indigenous species with exotic ones” replacement would be understood by most of the readers as a direct replacement where one species (invasive) outcompeted a native/endemic. This was not the case. In the Azores vegetation was destroyed and used and later invaded, invasive species were introduced mostly in “empty” landscapes.

5th Paragraph: “By contrast, exotic forests, which have been established in more easy-to-access areas, exhibit spatial traits that align with historical human activity and land-use change.” Easy to access areas were more easily used by humans (agriculture etc) and therefore invaded because they were empty…

On the “The canopy ...”

Complexity is here assumed in a static view but if native forest is older (even very optimistically stated as close to pristine…) and exotic younger then heterogeneity would be expected do to time alone, i.e. the exotic forests are still far from “mature” where “natives” are mature forests. Please discuss.

On the “temporal dynamics”

“The findings indicate a historical trajectory (...) from pristine native forest ecosystems to increasingly disturbed exotic stands.” This not the scope of this publication that does not include historical data, even less on pristine forest. Delete the sentence.

“Conservation efforts should prioritize protecting less accessible areas where native species have a competitive advantage. Conversely, restoration in exotic forests should aim to enhance structural resilience by controlling invasive species, particularly in the ground and canopy layers, while promoting native species to improve overall habitat quality”.

Results prove clearly that conservation efforts should prioritize invaded areas, promoting their conversion to a higher degree of “nativeness” and not to preserve what is already protected as stated by the authors as close to pristine.

Reviewer #3: (No Response)

**********

what does this mean? ). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy

Reviewer #1: No

Reviewer #2: No

Reviewer #3: No

**********

PLoS One. 2025 Jun 16;20(6):e0326304. doi: 10.1371/journal.pone.0326304.r005

Author response to Decision Letter 2

29 Apr 2025

I keep my comment on the title: The reader finds out that after all the study concerns one island out of nine islands, that needs to be addressed on the proposed title "Landscape to Microhabitat: Uncovering the Multiscale Complexity of Terceira Island forests (Azores, Portugal)". The authors have no data on the Azores just for 1/9 of the islands.

We agree that the title should accurately reflect the geographic extent of the study, which is limited to Terceira Island. Accordingly, we have revised the title to:

“Landscape to Microhabitat: Uncovering the Multiscale Complexity of Native and Exotic Forests on Terceira Island (Azores, Portugal)”

While our study focuses exclusively on Terceira Island, we emphasize in the manuscript that the findings are likely applicable to other Azorean islands. This is because Terceira hosts the most representative and best-preserved remnants of several types of native forest, as well as typical secondary and exotic forest types found throughout the archipelago. Given this ecological representativeness, we consider Terceira an appropriate model for broader ecological inferences across the Azores. We have now clarified this point more explicitly in the manuscript to ensure that readers properly understand the study’s wider relevance and contextual framework.

Abstract

By analysing landscape(…) we found that less accessible terrains are covered by the remnants of native forests. (…) plant species.

The authors are again stating that “they found” instead rephrase as:

We have revised the sentence in the abstract to avoid the assertive phrasing “we found.” The revised sentence now reads:

“Based on landscape, habitat, and microhabitat analyses, remnants of native forests appeared to be associated with less accessible terrains.”

The authors state: However, we recognize the limitation that precise historical land-use data are not available.

We agree that while detailed historical cartography may not be available, valuable descriptive and synthesized sources do exist. In response, we now have revised the manuscript to include previously missing relevant references that discuss historical ecosystem distribution in the Azores.

Abstract

We agree that our study does not include quantitative data on the effectiveness of protected area management or enforcement in the Azores as it was not our objective. To address this, we have revised the statement to remain within the scope of our findings. The sentence now reads:

“These insights emphasize the importance of long-term monitoring and structural assessments in informing conservation efforts aimed at preserving native forests and managing invasive species in exotic woodlands.”

While our field experience has exposed us to signs of inconsistent enforcement (e.g., cattle presence in some designated areas), such observations can be anecdotal and not sufficient to support empirical conclusions. We have therefore removed any implication that our data directly assess the effectiveness of protected area management.

Introduction

The authors state:

Delete “1841”

The date “1841” has been removed from the species citation for Cryptomeria japonica, and the sentence has been corrected accordingly.

We have incorporated references that provide data on land-use changes and the current extent of native forest areas across the archipelago.

Specifically, we now cite Castanho et al. (2021), which offers a detailed analysis of land-use trends in the Azores between 1990 and 2018, and Triantis et al. (2010), which includes estimates of the remaining native forest cover and the historical context of habitat loss. These sources support the statement regarding significant and dramatic alteration of native vegetation, which refers not only to the replacement by Cryptomeria japonica and Pittosporum undulatum but also to broader land-use conversion for agriculture, pastures, and other human activities.

Introduction ...consist primarily of broad-leaved evergreen trees. There are according to Elias (2016), Dias et al. (2021), and others several types of vegetation including some that are not broad-lead. To characterize the broad-leaved evergreen trees as such without any further hint or name is insufficient; include also the references: Dias, et al (2021). Vegetação dos Açores. In Capelo, J.; Aguiar, C. (Eds.), Vegetação de Portugal. Lisboa: INCM, p; Mucina, et al. "Vegetation of Europe: hierarchical floristic classification system of vascular plant, bryophyte, lichen, and algal communities". Applied Vegetation Science 19 (2016): 3-264; Fernández Prieto, et al. "Description of some new syntaxa from the Azores archipelago". International Journal of Geobotanical Research 2 1 (2012): 111-116. http://dx.doi.org/10.5616/ijgr120007

The references included in my first review need to be included, there can be no cancellation on authors views or scientific approaches to vegetation study.

Many thanks for remembering those references, we have now included the suggested sources—Dias et al. (2021), Mucina et al. (2016), and Fernández Prieto et al. (2012)—alongside the existing citations. Altogether, these references provide a global view of the diversity of vegetation types in the Azores, beyond the general characterisation of broad-leaved evergreen trees.

While we fully agree that native vegetation holds the highest ecological value and should be prioritized in conservation, we would like to clarify that our intent was not to equate the ecological importance of native and human-modified ecosystems, but rather to acknowledge the ecological roles that even altered landscapes can occasionally play.

To support this nuance, we refer to the study by Tsafack et al. (2021), which demonstrates that small patches of exotic forest—although human-modified—can serve as refuges for rare endemic arthropods. We have therefore revised the text to avoid any misinterpretation and to clarify that the ecological value of these systems is context-dependent and generally lower than that of native forests, but not necessarily negligible.

The revised sentence now reads:

“As a result, the Azores’s landscape has several patches of native and exotic woodlands in a matrix of agricultural fields [32,42–44], each contributing differently to the current ecological dynamics of the island.”

We hope this rephrasing addresses the concern while still reflecting the current complex ecological realities observed in the field.

Introduction

Although the authors revised the use of “mosaic” this part of the introduction still needs to be improved using numerical data on types of cover.

Following your previous comment, wee have enhanced the list of references in the Introduction. They now include sources that provide quantitative data and detailed descriptions of land-use types in the Azores. In particular, the study by Castanho et al. (2021) and Triantis et al (2010) offer comprehensive data on land-cover categories and their evolution over recent decades and has now been cited to support our characterization of the landscape mosaic. We chose not to duplicate these statistics directly in the Introduction, as such information can be found in the cited sources, allowing interested readers to consult the detail.

Material and Methods.

1st paragraph

“…vegetation which were dominated” rephrase as “vegetation which are dominated”

We have corrected the verb tense as recommended. The sentence now reads:

“…vegetation which are dominated…”

What’s the meaning of “primarily consisting” means that are sites not dominated by Pittosporum?

The expression “primarily consisting” was intended to indicate that the dominant woody species in the exotic forest plots is Pittosporum undulatum. To avoid ambiguity, we have revised the sentence to read:

“The remaining nine sites were situated in areas dominated by the invasive species Pittosporum undulatum.”

Vegetation survey

“The objective was to obtain comprehensive data on the composition of forest species.” Rephrase objectives do not fit M&M

We agree that objectives are generally not stated in the Materials and Methods section. However, this sentence refers specifically to the aim of the vegetation survey, not the overall study. To avoid confusion, we have rephrased the sentence for clarity and alignment with standard scientific writing:

“This survey aimed to collect detailed data on forest species composition across the study plots.”

Material and Methods.

I accept that a further change on the title (apart from the geographical restriction) is not need, but use this data (numerical data) where required (see comment above)

Following your previous comments, we confirm that this observation has been addressed in the revised manuscript.

Material and Methods. Study Area and Site selection

The authors in their reply refer to a table, I could not find the reference in the text.

The table referred to is included in the supplementary material, and we have now added an explicit reference to it in the main text to ensure clarity and accessibility for the reader.

Material and Methods.

Although the authors have improved the text concerning plots and time, both the difference in size and the 10 years difference need to be included in the discussion.

This seems to be a very poor, and not included, explanation.

The authors further reply: Similarly, (…) we believe the 10-year difference does not undermine this objective.

In my view this weakness on the methodological approach cannot be solved just by answering to the reviewers using private and unpublished information.

The authors have two choices to publish the information in the paper or to cite another source.

We have added a paragraph in the Discussion section addressing the limitations related to the time gap and the difference in plot size between the native and exotic vegetation surveys. We acknowledge that these differences may introduce a degree of uncertainty, particularly in comparing composition over time.

Regarding the vegetation data for native plots, the surveys were conducted using a standardized protocol as part of earlier projects (ISLANDBIODIV and MOVECLIM), and are based on peer-reviewed methodology (as cited in Borges et al. 2018, Global Island Monitoring Scheme). Although these data are from 2012–2013, the sites are in well-preserved, minimally disturbed forest areas within protected areas. These forests are known for their structural stability, and currently no more recent peer-reviewed vegetation surveys exist for these exact plots.

Moreover, the wood species composition and abundance from those plots is already available in the supplementary material of the publication below, that we now cite in the methods section.

Borges, P.A.V., Cardoso, P., Fattorini, S., Rigal, F., Matthews, T.J., Di Biase, L., Amorim, I.R., Florencio, M., Borda-de-Água, L., Rego, C., Pereira, F., Nunes, R., Carvalho, R., Ferreira, M.T., Lopez, H., Pérez Delgado, A.J., Otto, R., Fernández Lugo, S., Nascimento, L. de, Caujapé-Castells, J., Casquet, J., Danflous, S., Fournel, J., Sadeyen, A.-M., Elias, R.B., Fernández-Palacios, J.M., Oromí, P., Thébaud, C., Strasberg, D. & Emerson, B.C. (2018). Community structure of woody plants on islands along a bioclimatic gradient. Frontiers of Biogeography, 10(3-4): 1-31. DOI: 10.21425/F5FBG40295

As mentioned, new field sampling in these sensitive areas was avoided to prevent unnecessary disturbance to the forest structure, which is central to our study’s focus on structural complexity. We recognize this is a limitation and have now explicitly acknowledged it in the manuscript.

While we understand the reviewer’s concern, we believe that the combination of (i) the known stability of these forest systems, (ii) the location of plots in protected and undisturbed areas, and (iii) the use of a standardized and peer-reviewed vegetation survey protocol, provides a sufficient basis for using these data, while transparently communicating the limitation to readers.

Material and Methods. Vegetation Survey

Original comment: The exotic forest plots were surveyed in the spring of 2023 within 20 x 20 (…). Why are the plots different in size?

Homogeneity is a type of data, not shown in the paper, just assumed in the reply, if the authors can show or produce evidence of this

Attachment

Submitted filename: Reviews comments V4.docx

pone.0326304.s005.docx^{(30.9KB, docx)}

PLoS One. doi: 10.1371/journal.pone.0326304.r006

Decision Letter 2

Francesco Boscutti

28 May 2025

Landscape to microhabitat: uncovering the multiscale complexity of native and exotic forests on Terceira Island (Azores, Portugal)

PONE-D-24-59937R2

Dear Dr. Lhoumeau,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication.

An invoice will be generated when your article is formally accepted. Please note, if your institution has a publishing partnership with PLOS and your article meets the relevant criteria, all or part of your publication costs will be covered. Please make sure your user information is up-to-date by logging into Editorial Manager at Editorial Manager® and clicking the ‘Update My Information' link at the top of the page. If you have any questions relating to publication charges, please contact our Author Billing department directly at authorbilling@plos.org.

If your institution or institutions have a press office, please notify them about your upcoming paper to help maximize its impact. If they’ll be preparing press materials, please inform our press team as soon as possible -- no later than 48 hours after receiving the formal acceptance. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information, please contact onepress@plos.org.

Kind regards,

Francesco Boscutti

Academic Editor

PLOS ONE

Additional Editor Comments (optional):

Reviewers' comments:

PLoS One. doi: 10.1371/journal.pone.0326304.r007

Acceptance letter

Francesco Boscutti

PONE-D-24-59937R2

PLOS ONE

Dear Dr. Lhoumeau,

I'm pleased to inform you that your manuscript has been deemed suitable for publication in PLOS ONE. Congratulations! Your manuscript is now being handed over to our production team.

At this stage, our production department will prepare your paper for publication. This includes ensuring the following:

* All references, tables, and figures are properly cited

* All relevant supporting information is included in the manuscript submission,

* There are no issues that prevent the paper from being properly typeset

You will receive further instructions from the production team, including instructions on how to review your proof when it is ready. Please keep in mind that we are working through a large volume of accepted articles, so please give us a few days to review your paper and let you know the next and final steps.

Lastly, if your institution or institutions have a press office, please let them know about your upcoming paper now to help maximize its impact. If they'll be preparing press materials, please inform our press team within the next 48 hours. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information, please contact onepress@plos.org.

If we can help with anything else, please email us at customercare@plos.org.

Thank you for submitting your work to PLOS ONE and supporting open access.

Kind regards,

PLOS ONE Editorial Office Staff

on behalf of

Dr. Francesco Boscutti

Academic Editor

PLOS ONE

Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

S1 Data. Pre-processed data used during analysis.

(ZIP)

pone.0326304.s001.zip^{(135.5KB, zip)}

Attachment

Submitted filename: Comments on PONE_D_24_59937_Landscape to Microhabitat.pdf

pone.0326304.s002.pdf^{(477.3KB, pdf)}

Attachment

Submitted filename: Reviews comments V1_resubmission.docx

pone.0326304.s004.docx^{(45.1KB, docx)}

Attachment

Submitted filename: Reviews comments V4.docx

pone.0326304.s005.docx^{(30.9KB, docx)}

Data Availability Statement

Data are available in supplementary materials.

[pone.0326304.ref001] 1.Wildermuth B, Dönges C, Matevski D, Penanhoat A, Seifert CL, Seidel D, et al. Tree species identity, canopy structure and prey availability differentially affect canopy spider diversity and trophic composition. Oecologia. 2023;203(1–2):37–51. doi: 10.1007/s00442-023-05447-1 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0326304.ref002] 2.Renner SC, Gossner MM, Ayasse M, Böhm S, Teuscher M, Weisser WW, et al. Forest structure, plants, arthropods, scale, or birds’ functional groups: What key factor are forest birds responding to?. PLoS One. 2024;19(5):e0304421. doi: 10.1371/journal.pone.0304421 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0326304.ref003] 3.Sedjo RA. The carbon cycle and global forest ecosystem. Water Air Soil Pollut. 1993;70(1–4):295–307. doi: 10.1007/bf01105003 [DOI] [Google Scholar]

[pone.0326304.ref004] 4.Borges Silva LC, Pavão DC, Elias RB, Moura M, Ventura MA, Silva L. Taxonomic, structural diversity and carbon stocks in a gradient of island forests. Sci Rep. 2022;12(1):1038. doi: 10.1038/s41598-022-05045-w [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0326304.ref005] 5.Thompson ID, Okabe K, Tylianakis JM, Kumar P, Brockerhoff EG, Schellhorn NA, et al. Forest biodiversity and the delivery of ecosystem goods and services: translating science into policy. BioScience. 2011;61(12):972–81. doi: 10.1525/bio.2011.61.12.7 [DOI] [Google Scholar]

[pone.0326304.ref006] 6.Zellweger F, Coomes D, Lenoir J, Depauw L, Maes SL, Wulf M, et al. Seasonal drivers of understorey temperature buffering in temperate deciduous forests across Europe. Glob Ecol Biogeogr. 2019;28(12):1774–86. doi: 10.1111/geb.12991 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0326304.ref007] 7.Verheyen K, Gillerot L, Blondeel H, De Frenne P, De Pauw K, Depauw L, et al. Forest canopies as nature‐based solutions to mitigate global change effects on people and nature. Journal of Ecology. 2024;112(11):2451–61. doi: 10.1111/1365-2745.14345 [DOI] [Google Scholar]

[pone.0326304.ref008] 8.Martinez-Almoyna C, Calderòn-Sanou I, Lionnet C, Gielly L, Boyer F, Dufour P, et al. Vegetation structure and climate shape mountain arthropod distributions across trophic levels. J Anim Ecol. 2024;93(10):1510–23. doi: 10.1111/1365-2656.14164 [DOI] [PubMed] [Google Scholar]

[pone.0326304.ref009] 9.Schwarz J, Habel JC, Eberle J. Effects of habitat biotic features on hymenopteran diversity in East Africa. J Insect Conserv. 2024;28(4):821–30. doi: 10.1007/s10841-024-00604-0 [DOI] [Google Scholar]

[pone.0326304.ref010] 10.Wildermuth B, Penanhoat A, Sennhenn-Reulen H, Matevski D, Drescher J, Aubry-Kientz M, et al. Canopy structure influences arthropod communities within and beyond tree identity effects: Insights from combining LiDAR data, insecticidal fogging and machine learning regression modelling. Ecological Indicators. 2024;160:111901. doi: 10.1016/j.ecolind.2024.111901 [DOI] [Google Scholar]

[pone.0326304.ref011] 11.Storch F, Dormann CF, Bauhus J. Quantifying forest structural diversity based on large-scale inventory data: a new approach to support biodiversity monitoring. For Ecosyst. 2018;5(1). doi: 10.1186/s40663-018-0151-1 [DOI] [Google Scholar]

[pone.0326304.ref012] 12.Seidel D, Ehbrecht M, Dorji Y, Jambay J, Ammer C, Annighöfer P. Identifying architectural characteristics that determine tree structural complexity. Trees. 2019;33(3):911–9. doi: 10.1007/s00468-019-01827-4 [DOI] [Google Scholar]

[pone.0326304.ref013] 13.Pelt RV, Franklin JF. Influence of canopy structure on the understory environment in tall, old-growth, conifer forests. Can J For Res. 2000;30(8):1231–45. doi: 10.1139/x00-050 [DOI] [Google Scholar]

[pone.0326304.ref014] 14.Li Y, Li M, Li X, Liu Z, Ming A, Lan H, et al. The abundance and structure of deadwood: a comparison of mixed and thinned chinese fir plantations. Front Plant Sci. 2021;12:614695. doi: 10.3389/fpls.2021.614695 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0326304.ref015] 15.Bouget C, Cours J, Larrieu L, Parmain G, Müller J, Speckens V, et al. Trait-based response of deadwood and tree-related microhabitats to decline in temperate lowland and montane forests. Ecosystems. 2023;27(1):90–105. doi: 10.1007/s10021-023-00875-9 [DOI] [Google Scholar]

[pone.0326304.ref016] 16.Heidenreich MG, Seidel D. Assessing forest vitality and forest structure using 3d data: a case study from the hainich national park, Germany. Front For Glob Change. 2022;5. doi: 10.3389/ffgc.2022.929106 [DOI] [Google Scholar]

[pone.0326304.ref017] 17.Heidenreich MG, Höwler K, Seidel D. Towards an objective assessment of tree vitality: a case study based on 3D laser scanning. Trees. 2024;38(4):927–40. doi: 10.1007/s00468-024-02525-6 [DOI] [Google Scholar]

[pone.0326304.ref018] 18.Höwler K, Vallebuona N, Wern T, Ammer C, Seidel D. Structural reorganization in beech forests in central Germany as response to drought-induced mortality in the overstory. Trees, Forests and People. 2024;15:100506. doi: 10.1016/j.tfp.2024.100506 [DOI] [Google Scholar]

[pone.0326304.ref019] 19.Ehbrecht M, Seidel D, Annighöfer P, Kreft H, Köhler M, Zemp DC, et al. Global patterns and climatic controls of forest structural complexity. Nat Commun. 2021;12(1):519. doi: 10.1038/s41467-020-20767-z [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0326304.ref020] 20.Mueller-Dombois D. The formation of island ecosystems. GeoJournal. 1992;28(2). doi: 10.1007/bf00177244 [DOI] [Google Scholar]

[pone.0326304.ref021] 21.Kamijo T, Kitayama K, Sugawara A, Urushimichi S, Sasai K. Primary succession of the warm-temperate broad-leaved forest on a volcanic island, Miyake-jima, Japan. Folia Geobot. 2002;37(1):71–91. doi: 10.1007/bf02803192 [DOI] [Google Scholar]

[pone.0326304.ref022] 22.Fernández-Palacios JM, Kreft H, Irl SDH, Norder S, Ah-Peng C, Borges PAV, et al. Scientists’ warning - The outstanding biodiversity of islands is in peril. Glob Ecol Conserv. 2021;31:e01847. doi: 10.1016/j.gecco.2021.e01847 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0326304.ref023] 23.Keppel G, Buckley YM, Possingham HP. Drivers of lowland rain forest community assembly, species diversity and forest structure on islands in the tropical South Pacific. Journal of Ecology. 2009;98(1):87–95. doi: 10.1111/j.1365-2745.2009.01595.x [DOI] [Google Scholar]

[pone.0326304.ref024] 24.Helmer E, Ramos O, López TDM, Quinones M, Diaz W. Mapping the forest type and land cover of Puerto Rico, a component of the Caribbean biodiversity hotspot. Caribbean Journal of Science. 2002;38(3–4):165–83. Available from: https://research.fs.usda.gov/treesearch/30146 [Google Scholar]

[pone.0326304.ref025] 25.Benavides Rios E, Sadler J, Graham L, Matthews TJ. Species distribution models and island biogeography: Challenges and prospects. Global Ecology and Conservation. 2024;51:e02943. doi: 10.1016/j.gecco.2024.e02943 [DOI] [Google Scholar]

[pone.0326304.ref026] 26.Bermúdez AM, Fernández-Palacios JM, González-Mancebo JM, Patiño J, Arévalo JR, Otto R, et al. Floristic and structural recovery of a laurel forest community after clear-cutting: A 60 years chronosequence on La Palma (Canary Islands). Ann For Sci. 2007;64(1):109–19. doi: 10.1051/forest:2006094 [DOI] [Google Scholar]

[pone.0326304.ref027] 27.Bello-Rodríguez V, Cubas J, Del Arco MJ, Martín JL, González-Mancebo JM. Elevational and structural shifts in the treeline of an oceanic island (Tenerife, Canary Islands) in the context of global warming. International Journal of Applied Earth Observation and Geoinformation. 2019;82:101918. doi: 10.1016/j.jag.2019.101918 [DOI] [Google Scholar]

[pone.0326304.ref028] 28.Elias RB, Gil A, Silva L, Fernández-Palacios JM, Azevedo EB, Reis F. Natural zonal vegetation of the Azores Islands: characterization and potential distribution. phyto. 2016;46(2):107–23. doi: 10.1127/phyto/2016/0132 [DOI] [Google Scholar]

[pone.0326304.ref029] 29.Rull V, Lara A, Rubio-Inglés MJ, Giralt S, Gonçalves V, Raposeiro P, et al. Vegetation and landscape dynamics under natural and anthropogenic forcing on the Azores Islands: A 700-year pollen record from the São Miguel Island. Quaternary Science Reviews. 2017;159:155–68. doi: 10.1016/j.quascirev.2017.01.021 [DOI] [Google Scholar]

[pone.0326304.ref030] 30.Connor SE, van Leeuwen JFN, Rittenour TM, van der Knaap WO, Ammann B, Björck S. The ecological impact of oceanic island colonization – a palaeoecological perspective from the Azores. Journal of Biogeography. 2012;39(6):1007–23. doi: 10.1111/j.1365-2699.2011.02671.x [DOI] [Google Scholar]

[pone.0326304.ref031] 31.Tutin TG. The Vegetation of the Azores. The Journal of Ecology. 1953;41(1):53. doi: 10.2307/2257099 [DOI] [Google Scholar]

[pone.0326304.ref032] 32.Dias E, Mendes C, Melo C, Pereira D, Elias R. Azores central islands vegetation and flora field guide. Quercetea. 2005;7:123–73. [Google Scholar]

[pone.0326304.ref033] 33.Dias E, Mendes C, Aguiar C. Vegetação dos Açores. In: Capelo J, Aguiar C, editors. Árvores e florestas de Portugal. Lisboa: Imprensa Nacional-Casa da Moeda. 2021. p. 155–79. [Google Scholar]

[pone.0326304.ref034] 34.Mucina L, Bültmann H, Dierßen K, Theurillat J, Raus T, Čarni A, et al. Vegetation of Europe: hierarchical floristic classification system of vascular plant, bryophyte, lichen, and algal communities. Applied Vegetation Science. 2016;19(S1):3–264. doi: 10.1111/avsc.12257 [DOI] [Google Scholar]

[pone.0326304.ref035] 35.Fernández Prieto JA, Aguiar C, Dias E. Description of some new syntaxa from the Azores archipelago. International Journal of Geobotanical Research. 2012;2:111–6. [Google Scholar]

[pone.0326304.ref036] 36.Borges PAV, Costa A, Regina C, Gabriel R, Gonçalves V, Frias Martins A. A list of the terrestrial and marine biota from the Azores. Parede: Principia. 2010. [Google Scholar]

[pone.0326304.ref037] 37.Gabriel R, Bates JW. Bryophyte community composition and habitat specificity in the natural forests of Terceira, Azores. Plant Ecol. 2005;177(1):125–44. doi: 10.1007/s11258-005-2243-6 [DOI] [Google Scholar]

[pone.0326304.ref038] 38.Borges PAV, Lamelas-Lopez L, Andrade R, Lhoumeau S, Vieira V, Soares AO, et al. An updated checklist of Azorean arthropods (Arthropoda). Biodivers Data J. 2022;10:e97682. doi: 10.3897/BDJ.10.e97682 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0326304.ref039] 39.Raposeiro PM, Hernández A, Pla-Rabes S, Gonçalves V, Bao R, Sáez A, et al. Climate change facilitated the early colonization of the Azores Archipelago during medieval times. Proc Natl Acad Sci U S A. 2021;118(41):e2108236118. doi: 10.1073/pnas.2108236118 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0326304.ref040] 40.Rull V. Settlement and anthropization of the Azores Islands. Journal of Biogeography. 2023;50(12):2008–11. doi: 10.1111/jbi.14712 [DOI] [Google Scholar]

[pone.0326304.ref041] 41.Elias RB, Connor SE, Góis-Marques CA, Schaefer H, Silva L, Sequeira MM, et al. Is there solid evidence of widespread landscape disturbance in the Azores before the arrival of the Portuguese?. Proc Natl Acad Sci U S A. 2022;119(4):e2119218119. doi: 10.1073/pnas.2119218119 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0326304.ref042] 42.Connor SE, Lewis T, van Leeuwen JFN, van der Knaap WO, Schaefer H, Porch N, et al. Original plant diversity and ecosystems of a small, remote oceanic island (Corvo, Azores): Implications for biodiversity conservation. Biological Conservation. 2024;291:110512. doi: 10.1016/j.biocon.2024.110512 [DOI] [Google Scholar]

[pone.0326304.ref043] 43.Castanho RA, Naranjo Gómez JM, Couto G, Pimentel P, Sousa Á, Batista M da G. Analyzing the Patterns, Trends and Dynamics of the Land-Use Changes in Azores Region: From 1990 to 2018. Sustainability. 2021;13(10):5433. doi: 10.3390/su13105433 [DOI] [Google Scholar]

[pone.0326304.ref044] 44.Dias E, Elias RB, Nunes V. Vegetation mapping and nature conservation: a case study in Terceira Island (Azores). Biodiversity and Conservation. 2004;13(8):1519–39. doi: 10.1023/b:bioc.0000021326.50170.66 [DOI] [Google Scholar]

[pone.0326304.ref045] 45.Triantis KA, Borges PAV, Ladle RJ, Hortal J, Cardoso P, Gaspar C, et al. Extinction debt on oceanic islands. Ecography. 2010;33(2):285–94. doi: 10.1111/j.1600-0587.2010.06203.x [DOI] [Google Scholar]

[pone.0326304.ref046] 46.Lhoumeau S, Borges PAV. Assessing the Impact of Insect Decline in Islands: Exploring the Diversity and Community Patterns of Indigenous and Non-Indigenous Arthropods in the Azores Native Forest over 10 Years. Diversity. 2023;15(6):753. doi: 10.3390/d15060753 [DOI] [Google Scholar]

[pone.0326304.ref047] 47.Borges PAV, Lamelas-Lopez L, Stüben PE, Ros-Prieto A, Gabriel R, Boieiro M, et al. SLAM Project - Long Term Ecological Study of the Impacts of Climate Change in the Natural Forest of Azores: II - A survey of exotic arthropods in disturbed forest habitats. Biodivers Data J. 2022;10:e81410. doi: 10.3897/BDJ.10.e81410 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0326304.ref048] 48.Tsafack N, Fattorini S, Boieiro M, Rigal F, Ros-Prieto A, Ferreira MT, et al. The Role of Small Lowland Patches of Exotic Forests as Refuges of Rare Endemic Azorean Arthropods. Diversity. 2021;13(9):443. doi: 10.3390/d13090443 [DOI] [Google Scholar]

[pone.0326304.ref049] 49.Henriques D, Elias RB, Coelho MCM, Hernandéz RH, Pereira FEA, Gabriel R. Long-term monitoring across elevational gradients (III): vascular plants on Terceira Island (Azores) transect. 2017. [cited 25 Feb 2025]. Available from: http://hdl.handle.net/10400.3/4477 [Google Scholar]

[pone.0326304.ref050] 50.UNEP-WCMC. Protected Area Profile for Portugal from the World Database on Protected Areas. 2025. Available from: www.protectedplanet.net [Google Scholar]

[pone.0326304.ref051] 51.Costa R, Borges PAV. SLAM project - long term ecological study of the impacts of climate change in the natural forest of azores: i - the spiders from native forests of terceira and pico Islands (2012-2019). Biodivers Data J. 2021;9:e69924. doi: 10.3897/BDJ.9.e69924 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0326304.ref052] 52.Lhoumeau S, Cardoso P, Costa R, Boieiro M, Malumbres-Olarte J, Amorim I, et al. SLAM Project - long term ecological study of the impacts of climate change in the natural forest of Azores: IV - The spiders of Terceira and Pico Islands (2019-2021) and general diversity patterns after ten years of sampling. BDJ. 2022;10. doi: 10.3897/bdj.10.e96442 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0326304.ref053] 53.Lhoumeau S, Cardoso P, Boieiro M, Ros-Prieto A, Costa R, Lamelas-Lopez L, et al. SLAM Project - long term ecological study of the impacts of climate change in the natural forests of Azores: V - New records of terrestrial arthropods after ten years of SLAM sampling. Biodivers Data J. 2022;10:e97952. doi: 10.3897/BDJ.10.e97952 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0326304.ref054] 54.Seidel D, Stiers M, Ehbrecht M, Werning M, Annighöfer P. On the structural complexity of central European agroforestry systems: a quantitative assessment using terrestrial laser scanning in single-scan mode. Agroforest Syst. 2021;95(4):669–85. doi: 10.1007/s10457-021-00620-y [DOI] [Google Scholar]

[pone.0326304.ref055] 55.Parada-Díaz J, Fernández López ÁB, Gómez González LA, del Arco Aguilar MJ, González-Mancebo JM. Assessing the usefulness of LiDAR for monitoring the structure of a montane forest on a subtropical oceanic Island. Remote Sensing. 2022;14(4):994. doi: 10.3390/rs14040994 [DOI] [Google Scholar]

[pone.0326304.ref056] 56.Soto DP, Salas-Eljatib C, Donoso PJ, Hernández-Moreno Á, Seidel D, D’Amato AW. Impacts of varying precipitation regimes upon the structure, spatial patterns, and productivity of Nothofagus pumilio-dominated old-growth forests in Patagonia. Forest Ecology and Management. 2022;524:120519. doi: 10.1016/j.foreco.2022.120519 [DOI] [Google Scholar]

[pone.0326304.ref057] 57.Ehbrecht M, Schall P, Ammer C, Seidel D. Quantifying stand structural complexity and its relationship with forest management, tree species diversity and microclimate. Agricultural and Forest Meteorology. 2017;242:1–9. doi: 10.1016/j.agrformet.2017.04.012 [DOI] [Google Scholar]

[pone.0326304.ref058] 58.Willim K, Stiers M, Annighöfer P, Ammer C, Ehbrecht M, Kabal M, et al. Assessing understory complexity in beech-dominated forests (Fagus sylvatica L.) in central europe-from managed to primary forests. Sensors (Basel). 2019;19(7):1684. doi: 10.3390/s19071684 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0326304.ref059] 59.Zheng G, Moskal LM, Kim S-H. Retrieval of Effective Leaf Area Index in Heterogeneous Forests With Terrestrial Laser Scanning. IEEE Trans Geosci Remote Sensing. 2013;51(2):777–86. doi: 10.1109/tgrs.2012.2205003 [DOI] [Google Scholar]

[pone.0326304.ref060] 60.MacArthur RH, MacArthur JW. On bird species diversity. Ecology. 1961;42(3):594–8. doi: 10.2307/1932254 [DOI] [Google Scholar]

[pone.0326304.ref061] 61.Seidel D, Ehbrecht M, Puettmann K. Assessing different components of three-dimensional forest structure with single-scan terrestrial laser scanning: A case study. Forest Ecology and Management. 2016;381:196–208. doi: 10.1016/j.foreco.2016.09.036 [DOI] [Google Scholar]

[pone.0326304.ref062] 62.Ehbrecht M, Schall P, Juchheim J, Ammer C, Seidel D. Effective number of layers: A new measure for quantifying three-dimensional stand structure based on sampling with terrestrial LiDAR. Forest Ecology and Management. 2016;380:212–23. doi: 10.1016/j.foreco.2016.09.003 [DOI] [Google Scholar]

[pone.0326304.ref063] 63.Borges PAV, Cardoso P, Fattorini S, Rigal F, Matthews TJ, Di Biase L, et al. Community structure of woody plants on islands along a bioclimatic gradient. Frontiers of Biogeography. 2018;10(3–4). doi: 10.21425/f5fbg40295 [DOI] [Google Scholar]

[pone.0326304.ref064] 64.Borges PAV, Cardoso P, Kreft H, Whittaker RJ, Fattorini S, Emerson BC, et al. Global Island Monitoring Scheme (GIMS): a proposal for the long-term coordinated survey and monitoring of native island forest biota. Biodivers Conserv. 2018;27(10):2567–86. doi: 10.1007/s10531-018-1553-7 [DOI] [Google Scholar]

[pone.0326304.ref065] 65.Hill MO. Diversity and Evenness: A Unifying Notation and Its Consequences. Ecology. 1973;54(2):427–32. doi: 10.2307/1934352 [DOI] [Google Scholar]

[pone.0326304.ref066] 66.OpenTopography. Shuttle Radar Topography Mission (SRTM) Global. OpenTopography; 2013. doi: 10.5069/G9445JDF [DOI]

[pone.0326304.ref067] 67.Horn BKP. Hill shading and the reflectance map. Proceedings of the IEEE. 2008;69(1):14–47. 10.1109/PROC.1981.11918 [DOI] [Google Scholar]

[pone.0326304.ref068] 68.Bezanson J, Edelman A, Karpinski S, Shah VB. Julia: A Fresh Approach to Numerical Computing. SIAM Rev. 2017;59(1):65–98. doi: 10.1137/141000671 [DOI] [Google Scholar]

[pone.0326304.ref069] 69.R Core Team. R: A Language and Environment for Statistical Computing. Vienna, Austria: R Foundation for Statistical Computing; 2023. Available from: https://www.R-project.org/ [Google Scholar]

[pone.0326304.ref070] 70.Oksanen J, Kindt R, O’Hara B. The vegan package, Community ecology package. 2005. [Google Scholar]

[pone.0326304.ref071] 71.Harrell FE. Hmisc: Harrell Miscellaneous. 2024. Available from: https://CRAN.R-project.org/package=Hmisc [Google Scholar]

[pone.0326304.ref072] 72.Nock CA, Vogt RJ, Beisner BE. Functional Traits. 1st ed. In: John Wiley & Sons, Ltd, editor. eLS. 1st ed. Wiley; 2016. pp. 1–8. doi: 10.1002/9780470015902.a0026282 [DOI] [Google Scholar]

[pone.0326304.ref073] 73.Borges PAV, Gabriel R, Fattorini S. Biodiversity Erosion: Causes and Consequences. Encyclopedia of the UN Sustainable Development Goals. Springer International Publishing. 2019. p. 1–10. doi: 10.1007/978-3-319-71065-5_78-1 [DOI] [Google Scholar]

[pone.0326304.ref074] 74.Norder SJ, de Lima RF, de Nascimento L, Lim JY, Fernández-Palacios JM, Romeiras MM, et al. Global change in microcosms: Environmental and societal predictors of land cover change on the Atlantic Ocean Islands. Anthropocene. 2020;30:100242. doi: 10.1016/j.ancene.2020.100242 [DOI] [Google Scholar]

[pone.0326304.ref075] 75.Cazalis V, Princé K, Mihoub J-B, Kelly J, Butchart SHM, Rodrigues ASL. Effectiveness of protected areas in conserving tropical forest birds. Nat Commun. 2020;11(1):4461. doi: 10.1038/s41467-020-18230-0 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0326304.ref076] 76.Rahman MF, Islam K. Effectiveness of protected areas in reducing deforestation and forest fragmentation in Bangladesh. J Environ Manage. 2021;280:111711. doi: 10.1016/j.jenvman.2020.111711 [DOI] [PubMed] [Google Scholar]

[pone.0326304.ref077] 77.Vergílio M, Fonseca C, Calado H, Borges PAV, Elias RB, Gabriel R, et al. Assessing the efficiency of protected areas to represent biodiversity: a small island case study. Envir Conserv. 2016;43(4):337–49. doi: 10.1017/s037689291600014x [DOI] [Google Scholar]

[pone.0326304.ref078] 78.Singh M, Griaud C, Collins CM. An evaluation of the effectiveness of protected areas in Thailand. Ecological Indicators. 2021;125:107536. doi: 10.1016/j.ecolind.2021.107536 [DOI] [Google Scholar]

[pone.0326304.ref079] 79.Starnes T, Beresford AE, Buchanan GM, Lewis M, Hughes A, Gregory RD. The extent and effectiveness of protected areas in the UK. Global Ecology and Conservation. 2021;30:e01745. doi: 10.1016/j.gecco.2021.e01745 [DOI] [Google Scholar]

[pone.0326304.ref080] 80.Caujapé-Castells J, Tye A, Crawford DJ, Santos-Guerra A, Sakai A, Beaver K, et al. Conservation of oceanic island floras: Present and future global challenges. Perspectives in Plant Ecology, Evolution and Systematics. 2010;12(2):107–29. doi: 10.1016/j.ppees.2009.10.001 [DOI] [Google Scholar]

[pone.0326304.ref081] 81.Hortal J, Borges PAV, Jiménez-Valverde A, de Azevedo EB, Silva L. Assessing the areas under risk of invasion within islands through potential distribution modelling: The case of Pittosporum undulatum in São Miguel, Azores. Journal for Nature Conservation. 2010;18(4):247–57. doi: 10.1016/j.jnc.2009.11.002 [DOI] [Google Scholar]

[pone.0326304.ref082] 82.Silva LB, Alves M, Elias RB, Silva L. Comparison ofT-Square, Point Centered Quarter, andN-Tree Sampling Methods inPittosporum undulatumInvaded Woodlands. International Journal of Forestry Research. 2017;2017:1–13. doi: 10.1155/2017/2818132 [DOI] [Google Scholar]

[pone.0326304.ref083] 83.Heleno R, Lacerda I, Ramos JA, Memmott J. Evaluation of restoration effectiveness: community response to the removal of alien plants. Ecol Appl. 2010;20(5):1191–203. doi: 10.1890/09-1384.1 [DOI] [PubMed] [Google Scholar]

[pone.0326304.ref084] 84.Heleno RH, Ramos JA, Memmott J. Integration of exotic seeds into an Azorean seed dispersal network. Biol Invasions. 2012;15(5):1143–54. doi: 10.1007/s10530-012-0357-z [DOI] [Google Scholar]

[pone.0326304.ref085] 85.Borges PAV, Rigal F, Ros‐Prieto A, Cardoso P. Increase of insular exotic arthropod diversity is a fundamental dimension of the current biodiversity crisis. Insect Conserv Diversity. 2020;13(5):508–18. doi: 10.1111/icad.12431 [DOI] [Google Scholar]

[pone.0326304.ref086] 86.Lhoumeau S, Tsafack N, Manso S, Figueiredo T, Leite A, Parmentier L, et al. Monitoring arthropods under the scope of the LIFE-BEETLES project: I - Baseline data with implementation of the Index of Biotic Integrity. Biodivers Data J. 2024;12:e124799. doi: 10.3897/BDJ.12.e124799 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0326304.ref087] 87.Boieiro M, Matthews TJ, Rego C, Crespo L, Aguiar CAS, Cardoso P, et al. A comparative analysis of terrestrial arthropod assemblages from a relict forest unveils historical extinctions and colonization differences between two oceanic islands. PLoS One. 2018;13(4):e0195492. doi: 10.1371/journal.pone.0195492 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0326304.ref088] 88.Borges Silva L, Lourenço P, Teixeira A, Azevedo EB, Alves M, Elias RB, et al. Biomass valorization in the management of woody plant invaders: The case of Pittosporum undulatum in the Azores. Biomass and Bioenergy. 2018;109:155–65. doi: 10.1016/j.biombioe.2017.12.025 [DOI] [Google Scholar]

[pone.0326304.ref089] 89.Borges Silva L, Teixeira A, Alves M, Elias RB, Silva L. Tree age determination in the widespread woody plant invader Pittosporum undulatum. Forest Ecology and Management. 2017;400:457–67. doi: 10.1016/j.foreco.2017.06.027 [DOI] [Google Scholar]

[pone.0326304.ref090] 90.Dutra Silva L, Brito de Azevedo E, Bento Elias R, Silva L. Species Distribution Modeling: Comparison of Fixed and Mixed Effects Models Using INLA. IJGI. 2017;6(12):391. doi: 10.3390/ijgi6120391 [DOI] [Google Scholar]

[pone.0326304.ref091] 91.McGarigal K. FRAGSTATS: Spatial pattern analysis program for quantifying landscape structure. US Department of Agriculture, Forest Service, Pacific Northwest Research Station. 1995. [Google Scholar]

[pone.0326304.ref092] 92.Lenk A, Richter R, Kretz L, Wirth C. Effects of canopy gaps on microclimate, soil biological activity and their relationship in a European mixed floodplain forest. Sci Total Environ. 2024;941:173572. doi: 10.1016/j.scitotenv.2024.173572 [DOI] [PubMed] [Google Scholar]

[pone.0326304.ref093] 93.Richter T, Geres L, König S, Braziunas KH, Senf C, Thom D, et al. Effects of climate and forest development on habitat specialization and biodiversity in Central European mountain forests. Commun Biol. 2024;7(1):1518. doi: 10.1038/s42003-024-07239-6 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0326304.ref094] 94.Santos F, Valente MA, Miranda PM, Aguiar A, Azevedo E, Tomé A. Climate change scenarios in the Azores and Madeira Islands. World Resource Review. 2004;16:473–91. [Google Scholar]

[pone.0326304.ref095] 95.Ferreira MT, Cardoso P, Borges PAV, Gabriel R, de Azevedo EB, Reis F, et al. Effects of climate change on the distribution of indigenous species in oceanic islands (Azores). Climatic Change. 2016;138(3–4):603–15. doi: 10.1007/s10584-016-1754-6 [DOI] [Google Scholar]

[pone.0326304.ref096] 96.Goodland T, Healey JR. The invasion of Jamaican montane rainforests by the Australian tree Pittosporum undulatum. School of Agricultural and Forest Sciences, University of Wales Bangor. 1996. [Google Scholar]

[pone.0326304.ref097] 97.Bellingham PJ, Tanner EVJ, Martin PH, Healey JR, Burge OR. Endemic trees in a tropical biodiversity hotspot imperilled by an invasive tree. Biological Conservation. 2018;217:47–53. doi: 10.1016/j.biocon.2017.10.028 [DOI] [Google Scholar]

[pone.0326304.ref098] 98.Bellingham PJ, Tanner EVJ, Healey JR. Hurricane disturbance accelerates invasion by the alien tree Pittosporum undulatum in Jamaican montane rain forests. J Vegetation Science. 2005;16(6):675–84. doi: 10.1111/j.1654-1103.2005.tb02410.x [DOI] [Google Scholar]

[pone.0326304.ref099] 99.MacDougall AS, Gilbert B, Levine JM. Plant invasions and the niche. Journal of Ecology. 2009;97(4):609–15. doi: 10.1111/j.1365-2745.2009.01514.x [DOI] [Google Scholar]

[pone.0326304.ref100] 100.Tsafack N, Lhoumeau S, Ros-Prieto A, Navarro L, Kocsis T, Manso S, et al. Arthropod-based biotic integrity indices: A novel tool for evaluating the ecological condition of native forests in the Azores archipelago. Ecological Indicators. 2023;154:110592. doi: 10.1016/j.ecolind.2023.110592 [DOI] [Google Scholar]

[pone.0326304.ref101] 101.Belluau M, Paquette A, Gravel D, Reich PB, Stefanski A, Messier C. Exotics are more complementary over time in tree biodiversity–ecosystem functioning experiments. Functional Ecology. 2021;35(11):2550–61. doi: 10.1111/1365-2435.13900 [DOI] [Google Scholar]

[pone.0326304.ref102] 102.Davies KF, Chesson P, Harrison S, Inouye BD, Melbourne BA, Rice KJ. SPATIAL HETEROGENEITY EXPLAINS THE SCALE DEPENDENCE OF THE NATIVE–EXOTIC DIVERSITY RELATIONSHIP. Ecology. 2005;86(6):1602–10. doi: 10.1890/04-1196 [DOI] [Google Scholar]

[pone.0326304.ref103] 103.Borges PAV, Pimentel R, Carvalho R, Nunes R, Wallon S, Ros-Prieto A. Seasonal dynamics of arthropods in the humid native forests of Terceira Island (Azores). Arquipelago-Life and Marine Sciences. 2017;34:105–22. [Google Scholar]

[pone.0326304.ref104] 104.Gaspar C, Gaston KJ, Borges PAV, Cardoso P. Selection of priority areas for arthropod conservation in the Azores archipelago. J Insect Conserv. 2010;15(5):671–84. doi: 10.1007/s10841-010-9365-4 [DOI] [Google Scholar]

PERMALINK

Landscape to microhabitat: Uncovering the multiscale complexity of native and exotic forests on Terceira Island (Azores, Portugal)

Sébastien Lhoumeau

Rui B Elias

Dominik Seidel

Rosalina Gabriel

Paulo A V Borges

Roles

Abstract

Introduction

Materials and methods

Study area and site selection

Fig 1. Location of sampling sites.

Data acquisition

Terrestrial laser scanning

UAV canopy mapping

Vegetation survey

Sites and landscape characteristics

Data analysis

Fig 2. Visual representation of the group of variables considered.

Results

Table 1. Number of vascular plant species recorded in exotic and native plots according to their dominant strata and their colonisation status from [36].

Fig 3. NMDS Plot of Native vs. Exotic Forests on Terceira Island.

Fig 4. NMDS Plots of Traits by Forest Type.

Table 2. Spearman rank correlation coefficients of variables significantly correlated with a NMDS axis for a given forest trait.

Fig 5. Visual comparison of native and exotic woodlands.

Discussion

Landscape-level structure is a consequence of human accessibility and land-use

The structural complexity of forest stands is derived from different sources in native and exotic woodlands

The canopy of native forests shows greater structural and compositional homogeneity

Structural vulnerability varies between microhabitats

Temporal dynamics and conservation implications of forest change

Supporting information

Acknowledgments

Data Availability

Funding Statement

References

Author response to Decision Letter 0

Decision Letter 0

Francesco Boscutti

Roles

Author response to Decision Letter 1

Decision Letter 1

Francesco Boscutti

Roles

Author response to Decision Letter 2

Decision Letter 2

Francesco Boscutti

Roles

Acceptance letter

Francesco Boscutti

Roles

Associated Data

Supplementary Materials

Data Availability Statement

ACTIONS

PERMALINK

RESOURCES

Similar articles

Cited by other articles

Links to NCBI Databases