Impact of area closure on woody species diversity and soil physicochemical properties: evidence from Hulberag District, Central Ethiopia

Abstract

Background

Land degradation is a threat to global ecosystems and livelihoods of billions of people. Nearly 85% of Ethiopia’s land is degraded, costing more than USD 4.3 billion per year. Area closures for excluding human and livestock disturbances have been widely adopted as a restoration strategy for degraded lands to enable natural regeneration. However, integrated ecological and socio-economic assessments are scarce in the Siltie Zone of Central Ethiopia and evidence-based interventions are limited.

Methods

A comparative study design was used in the study area of Hulberag District, to assess 14-years-long area closures and adjacent open grazing lands. Data collection comprised vegetation surveys, physicochemical analyses of soils at different soil depths and household questionnaires. Statistical analysis was performed by ANOVA and post-hoc Tukey’s HSD tests to compare land-use types and topographic positions.

Results

Area closures significantly improved ecosystem metrics. Woody species richness increased by 200%, stem density increased by 154%, and Shannon diversity was significantly higher than in open grazing lands. Soil organic carbon increased by 50%, available phosphorus by 33%, and cation exchange capacity by 25%. Bulk density decreased by 19%, indicating reduced soil compaction and improved soil quality. The greatest improvements occurred on lower slopes. Surveys revealed strong community support, with 79.8% of respondents identifying livestock fodder as the primary benefit and 53.1% associating area closures with increased crop yields through improved erosion control.

Conclusions

Area closure represents an effective, low-cost intervention for restoring degraded semi-arid ecosystems in Ethiopia, promoting native woody vegetation recovery and enhancing soil fertility while providing tangible livelihood benefits. For long-term success, adaptive co-management frameworks that integrate clear resource-use guidelines, equitable benefit-sharing, and alignment with broader watershed conservation strategies are recommended.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12862-026-02552-6.

Background

Land degradation is one of the major worldwide environmental problems, impacting 3.2 billion people and contributing to more than 10% of the annual reduction in the global gross domestic product due to lost ecosystem services [1]. It is a major driver of biodiversity loss and a limitation to the progress to achieve the Sustainable Development Goals (SDGs) [1]. The problem is even more acute in Sub-Saharan Africa where declining land productivity exacerbates poverty, food insecurity and environmental vulnerability [2]. Ethiopia is one of the most impacted countries in the region. According to the recent estimates, almost 85% of the country’s area is vulnerable to degradation with an annual economic loss estimated to be USD 4.3 billion [3]. This is especially true for the Ethiopian highlands, which accommodate a large proportion of the population and agricultural production. In this case, population pressure, agricultural expansion, deforestation, overgrazing, and climate variability make the highlands more vulnerable [4]. These pressures set off a vicious cycle of declining land productivity and increasing exploitation of natural resources, resulting in ongoing ecosystem degradation [5].

To tackle these challenges, Ethiopia has been implementing large scale land restoration programs for the last four decades. One of the most common interventions implemented is the establishment of area closures (also called exclosures) where degraded communal lands are protected from free grazing, wood harvesting and other disturbances so as to promote natural regeneration [6]. This restoration approach aligns with national initiatives such as the Climate Resilient Green Economy (CRGE) strategy and international commitments including the African Forest Landscape Restoration Initiative (AFR100), under which Ethiopia has pledged to restore millions of hectares of degraded land by 2030 [7].

Numerous studies have documented the ecological benefits of area closures across Ethiopia. Previous research has reported improvements in woody species diversity, vegetation structure, soil organic carbon, nutrient availability, and soil physical properties following protection from grazing and human disturbance [8–12]. For example, Yimer et al. [10] reported significant improvements in soil quality within exclosures in the Central Rift Valley, while Fikadu and Argaw [11] documented enhanced woody species diversity in southwestern Ethiopia. More recently, Mathewos and Mamo [12] and Tesfay et al. [13] demonstrated positive effects of exclosures on both woody vegetation and soil properties in the Rift Valley Basin and central Tigray, respectively. Nevertheless, restoration outcomes vary considerably across locations because they are influenced by factors such as climate, soil characteristics, topography, management history, and the duration of protection [8].

Although the ecological benefits of area closures are well documented, important knowledge gaps remain regarding their integrated ecological and socio-economic impacts. Previous studies have generally focused on either vegetation recovery, soil improvement, or community perceptions separately. In Hulberag District, Yimam [14] assessed woody species composition and local community perceptions of area closures, providing valuable information on vegetation recovery and social attitudes. However, that study did not evaluate soil physicochemical properties or examine how restoration outcomes vary across topographic positions. Similarly, Wolka et al. [15] investigated the effects of area closures on soil properties in the south-central highlands of Ethiopia but did not incorporate vegetation assessments or community perspectives. Gemechu et al. [16] examined both woody species diversity and selected soil physicochemical properties in the Warja Watershed of eastern Ethiopia; however, their study did not include socio-economic dimensions or evaluate restoration responses across topographic gradients. Likewise, Mathewos and Mamo [12] focused primarily on soil and vegetation responses without integrating community perceptions. Consequently, there remains limited understanding of how ecological recovery and local perceptions interact within a single analytical framework, particularly in the Siltie Zone of Central Ethiopia.

Another important gap concerns the role of topographic position in shaping restoration outcomes. Topography strongly influences soil moisture distribution, nutrient accumulation, erosion processes, and vegetation establishment, yet relatively few Ethiopian exclosure studies have explicitly examined restoration responses across upper, middle, and lower slope positions [13, 17]. Understanding these spatial variations is important for designing more efficient and targeted restoration strategies.

The current study was designed to fill these gaps, by providing a comprehensive assessment of a 14 years area closure in Hulberag District of Central Ethiopia. Therefore, unlike previous studies conducted in the area and other parts of Ethiopia, this study is unique in the sense that it integrates three related aspects simultaneously, i.e., (i) woody species diversity and composition, (ii) soil physicochemical properties at different soil depths and topographical locations, and (iii) community perceptions on ecological and livelihood benefits of area closures. The study integrates these elements into a single comparative framework, allowing for a more comprehensive assessment of restoration outcomes than has been possible in the Siltie Zone. Therefore, the objectives of this study were to: (1) quantify the effects of area closure on woody species diversity and composition; (2) assess changes in soil physicochemical properties across soil depths and topographic positions; and (3) examine community perceptions of area closures and their perceived livelihood benefits. The study contributes new evidence on the interactions between vegetation recovery, soil restoration, and local perceptions, while providing the first integrated assessment of these dimensions in Hulberag District and the wider Siltie Zone of Central Ethiopia. This information is expected to support evidence-based restoration planning and sustainable land management in similar highland environments.

Methods

Study area

The intended study was conducted in the Hulberag District, which is located in the Siltie Zone of the Central Ethiopia regional state, Ethiopia. The district covers nearly 335.56 km², with an elevation ranging from 1,800 to 2,426 m amsl. The climate is characterized by a bimodal rainfall pattern, with yearly precipitation between 901 and 1,410 mm and mean temperatures of 11–23 °C. Main soil types of Hulberag district are Nitisols and Cambisols. The local economy mainly relies on smallholder mixed crop-livestock farming. In response to widespread degradation, community-managed area closures were started in 2007 and currently protect an estimated area of 14,200 hectares (Fig. 1).

Fig. 1.

Study area map showing Shama area closure in Central Ethiopia

Study design and sampling

This study used a comparative research design where 14-year-old area closures because this represents the median age of exclosures in Hulberag District (range: 8–22 years), previous research [6, 17] indicates that significant vegetation and soil carbon recovery typically occurs within 10–15 years of closure, younger exclosures (< 8 years) in the district were insufficiently established for reliable vegetation sampling, and older exclosures (> 20 years) were limited in number and spatial extent. were matched with adjacent open grazing lands with similar slope (± 5%), aspect (± 15°), elevation (± 50 m), and soil type (Nitisols/Cambisols). Two kebeles, namely, Ambrecho Achemo and Werabet Shama, were purposively selected. A total of 54 circular plots of 20 m diameter were established, with 27 plots of each land type systematically arranged along the transects of the two kebeles. Inclusion of multiple-age classes area closure would strengthen inferences about temporal dynamics, and that is recommended for future research.

Vegetation Survey: All woody plants with a height of 0.5 m and above were identified, counted, and measured for DBH and total height. Plant identification was carried out by A botanist of Ethiopian flora, conducted all species identifications. All specimen vouchers were placed in the National Herbarium of Ethiopia (ETH) at Addis Ababa University. As a limitation, some species could only be identified using morphological features and were not molecularly confirmed. Sterile specimens frequently could not be identified to species level alone; when this occurred, the genus level was used and verified against fertile specimens from nearby locations.

Soil Sampling: Soil samples were collected at two depths of 0–20 cm and 20–40 cm at the center of each plot, resulting in 108 composite samples (54 plots × 2 depths). Permission to collect woody species and soil samples was granted by the Hulberag District Agriculture Office and the local kebele administrations. The study sites were on communal land. Verbal consent for vegetation and soil sampling was obtained from community representatives following the traditional ‘Edire’ system of communal resource governance, where elected community leaders represent collective land use decisions.

Household Survey: A structured questionnaire (see Supplementary File: Questionnaire S1) was used to interview 295 households selected using systematic random sampling. Qualitative data were collected through focus group discussions (n = 4 groups, 8–10 participants each) and key informant interviews (n = 12), guided by checklists.

Sample size determination

The study employed both qualitative and quantitative data collection methods to investigate local community perceptions of area closure in detail. A sufficient and representative number of respondents were selected from total households using systematic random sampling. To determine the proper sample size from the total households, the formula by [18] was applied:

Where:

• = sample size.

• = number of total households (1120).

• = precision or error limit (0.05).

Thus:

Accordingly, 295 sample respondents were taken from the total population. Quantitative data were collected from these 295 respondents using questionnaires. Qualitative data were collected through direct observation, key informant interviews, and focus group discussions, guided by checklists.

Data analysis

Vegetation data were used to calculate species richness, stem density, basal area, Importance Value Index (IVI), and diversity indices such as Shannon-Wiener and Simpson. Soil physicochemical properties were subjected to two-way ANOVA to assess significant differences (p < 0.05) between land use types, slope positions, and depths. Post-hoc tests were done using the Tukey’s HSD test. Socio-economic data were described using summary statistics. All analyses were performed using the R statistical program version 4.2.1. ANOVA and post-hoc tests using the Tukey HSD were done using the stats and agricolae packages, while the vegan package was used to compute the diversity indices.

Results

Socio-demographic characteristics of respondents

Community perceptions on area closure are shaped by socio-demographic factors of the community, which in turn inform land management decisions and conservation acceptability. The majority of the respondents, 67%, were from the economically active population group of 20–40 years old. Most of the respondents, 81.8%, had a low level of formal education, and the study participants were predominantly male, 72.7% (Table 1).

Table 1.

Socio-demographic characteristics of surveyed households (N = 295)

Variable	Category	Frequency (N)	Percentage (%)
Gender	Male	216	72.7
	Female	81	27.3
Age Distribution	< 20 years	12	4.0
	20–40 years	199	67.0
	40–60 years	77	25.9
	> 60 years	9	3.0
Educational Status	Illiterate	115	38.7
	Read and Write only	128	43.1
	Certificate/Diploma	53	17.8
	Degree and above	1	0.3
Family Size	1–3 members	58	19.5
	4–5 members	148	49.8
	6–10 members	73	24.6
	> 10 members	18	6.1

Livelihood benefits derived from area closures

Area closures offered multiple ecosystem services, which were essential for local livelihoods. The respondents were given an option to choose multiple benefits, with livestock fodder being the most common (79.8%), followed by honey production (29.6%), construction materials (22.2%), fuelwood (20.5%), and medicinal plants (18.2%) (Table 2).

Table 2.

Community-reported provisioning benefits from area closures (N = 295)

Rank	Benefit Type	Frequency	Percentage (%)
1	Livestock Fodder	237	79.8
2	Apiculture (Honey)	88	29.6
3	Construction Materials	66	22.2
4	Firewood and Charcoal	61	20.5
5	Medicinal Plants	54	18.2

Statistical analysis of socio-demographic influences: Chi-square tests revealed that perceived benefits varied significantly by gender (χ² = 8.34, df = 1, p = 0.004) and educational status (χ² = 12.67, df = 3, p = 0.005). Male respondents were more likely to report livestock fodder (85.2% of males vs. 65.4% of females), while females reported medicinal plants more frequently (28.4% vs. 14.8%). Respondents with formal education (certificate/diploma or above) were significantly more likely to recognize apiculture as a benefit (42.6%) compared to illiterate respondents (21.7%; p < 0.01). Age and family size showed no significant association with perceived benefit types (p > 0.05).

Perceived drivers of agricultural yield improvement

The results of the study show that among respondents reporting higher crop yields (n = 245), 53.1% attributed the increase to gully rehabilitation and erosion control facilitated by area closures. Other perceived factors included reduced soil erosion (34.7%) and improved soil moisture (9.4%) (Table 3).

Table 3.

Perceived environmental factors contributing to increased crop yields (n = 245)

Perceived driver	Frequency	Percentage (%)
Rehabilitation of Gullies	130	53.1
Minimization of Soil Erosion	85	34.7
Improved Soil Moisture	23	9.4
Other factors	7	2.8

Woody species diversity and composition

Area closures had significantly higher woody species diversity than the open grazing lands. A total of 24 species were recorded from the area closures, while only 8 species were present in the open lands. The average species richness per plot was significantly higher in the area closures (16 ± 2.3) than in the open lands (5.3 ± 1.1; p < 0.001). Stem density was also significantly higher in the area closures (167.3 ± 17.03 stems/ha) than in the open lands (66 ± 8.2 stems/ha; p < 0.001). The Shannon diversity index was also higher in the area closures (H′ = 3.36 ± 0.12) than in the open lands (H′ = 3.13 ± 0.15; p < 0.05). Euclea schimperi was the dominant species in the area closures with IVI = 47.2, followed by Dodonaea angustifolia and Acacia saligna. However, the open lands were dominated by Carissa spinarum with IVI = 52.1, indicating a simpler, more degraded community structure. The IVI, which combines relative density, relative frequency, and relative dominance, provides a comprehensive measure of a species’ ecological importance. The higher IVI of pioneer species in closures reflects successful natural regeneration following livestock exclusion. These findings are consistent with Fikadu and Argaw [11], who reported a tripling of woody species richness in exclosures in Lemo, southwestern Ethiopia. Similarly, Tesfay et al. [13] documented higher Shannon diversity indices (H′ = 3.28) in exclosures of semi-arid Central Tigray, closely matching our H′ = 3.36. Yimer et al. [10] also found significantly higher species densities in exclosures compared to open grazing lands in the Central Rift Valley, corroborating our observed 154% increase in stem density (Table 4).

Table 4.

Dominant woody species in area closures (n = 6 plots per species assessment)

Species	Total Count	Plots Present	Frequency (% of plots)	Mean Abundance
Euclea schimperi	47	4	66.7	7.83
Dodonaea angustifolia	22	2	33.3	7.33
Acacia saligna	18	4	66.7	3.00

Topographic influence on woody species metrics

A clear topographic gradient was observed for both species richness and stem density, with values always being highest on lower slopes and decreasing towards upper slopes (Fig. 2). The enhancement effect of area closure was observed to be greatest on lower slopes, where stem density in closed areas was greater than 2.4 times that of open grazing lands. This pattern likely reflects downslope accumulation of water, nutrients, and organic matter, as well as reduced erosion stress. Woody species richness and stem density exhibited a clear topographic gradient with values gradually increasing from upper to lower slope positions under area closures. The richness within the area closure rised from 10.5 species per plot on upper slopes to 12.5 species per plot on middle slopes and 14.8 species per plot on lower slopes, a 41% increase in richness from upper to lower positions. Stem density followed a similar trend, increasing from 150 stems/ha on upper slopes to 169 stems/ha on middle slopes and 376 stems/ha on lower slopes, a 150% increase across the topographic gradient.

Fig. 2.

Topographic influence on woody species metrics

In contrast, significantly lower values were observed in open grazing lands, such as species richness of 4.8 species per plot on upper slopes and stem density of 58 stems/ha on upper slopes. The enhancement effect of area closure was highest on lower slopes, with a stem density (376 stems/ha) more than six times that of upper slopes of open grazing lands (58 stems/ha) and more than two times the stem density within the closure on middle slopes (169 stems/ha). The topographic pattern probably reflects downslope accumulation of water, nutrients and organic matter, combined with less erosion stress and more favorable microclimatic conditions for woody plant establishment and growth on lower slope positions.

The results are consistent with Tesfay et al. [13], who reported significantly higher woody species diversity and stem density in exclosures than open grazing lands in semi-arid Central Tigray, with the lower slopes showing the greatest recovery. Similarly, Yimer et al. [10] reported that exclosures in the Central Rift Valley of Ethiopia had significantly improved soil properties and vegetation recovery compared to open grazing lands, with the topographic position strongly influencing restoration outcomes (Fig. 2).

Soil physicochemical properties

The physicochemical properties of the soil were enhanced under area closure. The important soil fertility parameters like Soil Organic Carbon (50% increase), Total Nitrogen (83%), and Available Phosphorus (33%) were higher in the closure areas. In addition, the soil bulk density was reduced by 19% in the closure areas, and the Cation Exchange Capacity (CEC) was higher by 25%, which indicated improved nutrient retention capacity. These values were higher in the surface horizon (0–20 cm). Figure 3 presents a visual comparison of the important soil health parameters across different land uses, which are sometimes categorized on the basis of soil depth (Fig. 3).

Fig. 3.

Soil physicochemical properties by land use and depth

Discussion

This study offers robust evidence of the effectiveness of the use of area closure as a viable nature-based solution for the restoration of degraded semi-arid ecosystems in Ethiopia. The results of this study indicate the concurrent recovery of vegetation and soil properties, as suggested by the theory of restoration ecology and previous studies undertaken in northern Ethiopia [6, 8, 9]. The substantial increases observed in species diversity and stem densities within the exclosures also indicate the viability of passive restoration approaches where anthropogenic influences are removed, as suggested by global studies on the effectiveness of natural regeneration as a viable restoration tool, as effective as active planting, in ecosystems with some level of ecological memory [19]. The study findings are consistent with recent regional studies that have documented similar restoration trajectories. For instance, Yimam [14] reported improved woody species composition in Hulberag District exclosures, although that study did not integrate soil analysis. Wolka et al. [15] demonstrated significant soil property improvements following area closure in south-central Ethiopian highlands, corroborating our 50% increase in soil organic carbon. Likewise, Mathewos and Mamo [12] found that exclosures in the South Rift Valley Basin improved both woody species diversity and soil physicochemical properties, with a magnitude of change comparable to our observations. By explicitly linking vegetation recovery, soil restoration, and topographic position within a single analytical framework, the present study extends these earlier regional findings and provides a more integrated assessment than previously available for the Siltie Zone of Central Ethiopia.

The dominance of Euclea schimperi, a drought-resistant pioneer species, also corroborates the expected patterns of secondary succession in degraded drylands [20]. Pioneer species are known to play a vital role in the restoration of degraded ecosystems, as they help to stabilize the soil and create microclimates conducive to the establishment of other species [21].

This strong topographic gradient in restoration activity, with lower slope positions showing the greatest levels of improvement, points to underlying eco-hydrological processes. These areas naturally receive water and nutrient inputs from higher slope positions and thus tend to have more favorable conditions for plant growth and establishment [22]. The study result shows that stem density on lower slopes within the closure (376 stems/ha) was more than six times that of upper slopes in open grazing lands (58 stems/ha) provides quantitative evidence of how restoration outcomes vary spatially. This topographic dependency has been underemphasized in previous Ethiopian exclosure studies [13, 14], and our findings suggest that restoration planning could be optimized by prioritizing lower slope positions as potential nucleation sites.

The significant improvement in soil health within closures is important for long-term ecosystem resilience and functional recovery. The 50% improvement in soil organic carbon levels points to significant levels of carbon sequestration, which is important for mitigating climate change while also improving soil fertility and structure [23]. This improvement is likely due to increased litterfall from newly established vegetation, which is a well-known positive feedback process in restoration ecology [24]. The reduction in bulk density points to reduced levels of compaction, likely due to lower levels of livestock trampling and increased root growth, which is especially important in moisture-limited environments [25].

The positive community perception of area closure, particularly the value of fodder and erosion control, supports the social-ecological feasibility of this restoration method. The integration of ecological and socio-economic objectives transcends the restrictive conservation paradigm, which frequently leads to conflict [11, 26]. The community’s focus on fodder is consistent with livelihood requirements and the process of ecological succession, in which herbaceous vegetation regenerates before the dominance of woody vegetation [27]. This sequence facilitates adaptive management, in which initial focus on controlled grass harvest can sustain community support, with progressive transition to sustainable woody product use as the ecosystem develops [28].

This study differs from previous exclosure studies conducted in Ethiopia in that it combines three complementary dimensions including woody species diversity, soil physicochemical properties and community perceptions. Previous studies in the Siltie Zone [14] have focused only on vegetation, while regional studies [12, 13, 15] have focused mainly on either soil or vegetation without community perspectives. By comparison, the current study provides an authentic interdisciplinary appraisal. Our explicit assessment of restoration outcomes across upper, middle and lower slope positions also fills a notable gap identified by Tesfay et al. [13] and Mekuria and Aynekulu [8] who called for more spatially explicit restoration monitoring.

However, several limitations warrant acknowledgment. The space-for-time substitution design, while practical, cannot fully establish causality, and unmeasured confounding factors (e.g., historical land use differences, microclimatic variation) may have contributed to observed differences between closed and open sites. Our claim regarding cost-effectiveness is specific to the Ethiopian highlands context and should not be universally generalized without local validation. While area closures performed well under the biophysical and socio-economic conditions of Hulberag District, restoration outcomes are known to vary with rainfall regime, soil type, enforcement history, and community institutional arrangements [8, 13]. Therefore, we do not assert that area closures are universally successful, but rather that they represent a promising intervention where conditions for natural regeneration remain intact and community governance structures are functional.

The originality of this study lies in its integrated, multi-dimensional assessment for the understudied Central Ethiopia region. However, the absence of baseline data before closure establishment remains a constraint, and future longitudinal studies are needed to confirm the temporal trajectories inferred from our space-for-time comparison. Additionally, though 14-year-old closure provides valuable medium-term insights, inclusion of multiple age classes would strengthen inferences about long-term dynamics that is recommend for future research.

From a policy viewpoint, area closures provide a cost-effective strategy for achieving Ethiopia’s restoration targets through initiatives such as AFR100 [7, 29]. As per the findings of the study, six specific integration strategies were recommended. (i) Implement topography-based restoration zoning by prioritizing lower slope positions for initial closure establishment, as these areas showed 150% greater stem density and can serve as restoration nuclei. (ii) integrate exclosures with gully rehabilitation programs, since 53.1% of farmers attributed crop yield increases to gully rehabilitation and 34.7% to reduced erosion. (iii) Formalize community co-management through the existing Edire governance system, with gender-sensitive benefit-sharing mechanisms that address differential resource use patterns. (iv) Establish a phased restoration timeline spanning 0–25 years, progressing from establishment through herbaceous recovery, woody regeneration, and mature exclosure phases. (v) Align exclosures with national policy frameworks, including AFR100 and CRGE, while developing payment for ecosystem services schemes such as carbon credits, given the 50% increase in soil organic carbon. (vi) Implement participatory monitoring with five-year evaluations of vegetation and soil properties and annual household surveys to track socio-economic outcomes, including fodder and honey production.

Conclusions

The study “Impact of Area Closure on Woody Species Diversity and Soil Physicochemical Properties” in Hulberag District, Central Ethiopia, has successfully achieved three core objectives. The closure resulted in a threefold increase in woody species richness (8 to 24), a 154% increase in stem density (66 to 167.3 stems per hectare), and an increase in the Shannon diversity index from 3.13 to 3.36. Dominated confirming natural regeneration of pioneer species such as Euclea Schimperi. As for soil properties, the closure increased the soil organic carbon by 50% (2.05 to 3.07%), total nitrogen by 83%, available phosphorus by 33% (8.4 to 11.2 ppm) and the cation exchange capacity by 25% (18.3 to 22.8 cmolc/kg). It also reduced bulk density by 19% (from 1.52 to 1.28 g per cm3). Greatest gains were in the surface layer and on lower slopes where stem density increased 150%. Concerning community perceptions, 79.8% of respondents identified livestock fodder as the most valued resource, 29.6% identified honey production, and 53.1% of households with increased crop yields attributed this to gully rehabilitation and erosion control from the closure. The perceived benefits differed across gender and education lines, indicating the need for gender-sensitive benefit sharing. Key limitations include the absence of baseline data before closure establishment, a space-for-time substitution design that cannot fully confirm causality, and the use of a single 14-year old closure without multiple age classes to assess long-term dynamics. Including multiple-age classes in area closures would strengthen inferences about temporal dynamics and is recommended for future research.

Study limitations

Absence of baseline data from before the closure’s establishment, which hinders direct assessment of restoration trajectories. Space-for-time substitution design, which cannot fully confirm causality. Use of a single 14-year-old closure, without multiple age classes to assess long-term dynamics. Although efforts were made to match sites based on environmental characteristics, unmeasured factors may have contributed to observed differences. Including multiple age classes in area closures would strengthen inferences about temporal dynamics and is recommended for future research. Future longitudinal studies are also needed to confirm restoration dynamics over time.

Supplementary Information

Below is the link to the electronic supplementary material.

Abbreviations

AFR100

African Forest Landscape Restoration Initiative

ANOVA

Analysis of Variance

CEC

Cation Exchange Capacity

CRGE

Climate Resilient Green Economy

DBH

Diameter at Breast Height

ETH

National Herbarium of Ethiopia (Addis Ababa University)

FGD

Focus Group Discussion

HSD

Honestly Significant Difference

IVI

Importance Value Index

OC

Organic Carbon

PES

Payment for Ecosystem Services

SDG

Sustainable Development Goals

TN

Total Nitrogen

Author contributions

AH: Conceptualization, Methodology, Investigation, Data Curation, Writing-Original Draft.HM: Methodology, Formal Analysis, Validation, Writing-Review & Editing, Visualization.AK: Resources, Supervision, Project Administration, Funding Acquisition.TK: Formal Analysis, Data Curation, Writing-Review & Editing, Visualization.All authors read and approved the final manuscript.

Funding

This research was supported by Werabe University through the Natural Resource Management Research Grant (WRU/NRM/014/2022). The funder had no role in study design, data collection, analysis, interpretation, or manuscript preparation.

Data availability

The datasets generated and analyzed during this study are available from the corresponding author upon reasonable request.

Declarations

Ethics approval and consent to participate

This study received approval from Werabe University Research Ethics Committee (Reference: (WRU/NRM/014/2022). This study was conducted in accordance with the ethical principles of the Declaration of Helsinki. Permissions for vegetation and soil sampling was obtained from the Hulberag District Agriculture Office and local community leaders. All activities complied with local regulations and community agreements. Informed consent was obtained from all survey participants and community representatives prior to data collection.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.