Role of environmental variables on plant community formation in simien mountains national park afromontane vegetation

Abstract

Simien Mountains National Park, a UNESCO World Heritage Site, supports fragile Afromontane ecosystems, yet detailed information on its vegetation ecology remains limited. This study employed 139 stratified systematic sampling plots to characterize plant communities and examine relationships between vegetation and selected environmental variables. Plant communities were classified using hierarchical cluster analysis and plant–environment relationships were explored through ordination techniques. A total of 354 vascular plant taxa, representing 91 families, were recorded. Herbs constituted the dominant growth form (61.86%). Species richness was highest in Asteraceae (16%). Endemism was notable (12.2%), including seven species restricted to SMNP, underscoring the park’s national conservation importance. Cluster analysis identified four plant communities distributed along an elevational gradient of 2244–3150 m a.s.l. All communities exhibited relatively high diversity (Shannon index: 4.03–4.50; Fisher’s α: 25.4–35.1) and moderate compositional turnover (Jaccard similarity: 0.28–0.64), indicating substantial ecological heterogeneity. Canonical correspondence analysis showed altitude was the strongest environmental variable responsible for patterns of plant community formation, followed by soil properties, slope, and pH. Results demonstrate that SMNP supports rich species composition, endemism, and with spatial variation in vegetation composition. These findings provide a quantitative ecological baseline that can inform site-specific conservation planning and future monitoring.

Supplementary Information

The online version contains supplementary material available at 10.1038/s41598-025-34916-1.

Introduction

Ethiopia is renowned for its remarkable topographic diversity, which encompasses lofty mountains, flat-topped plateaus, deep gorges, river valleys, and plains¹. This diverse relief makes the country unique in Africa. The altitude spans from the highest summit of Ras Dejen (4,550 m a.s.l) in Gondar to the Danakil depression (110 m a. s.l.)^2,3. The highlands, above 1,500 m, constitute approximately half of the country’s total area⁴. The heterogeneous nature of land resources creates varied ecological conditions that support diverse ecosystems and a wide range of biodiversity². The abundance of flora and fauna in Ethiopia is largely attributed to its diverse ecological settings, climate, and topography.

The flora of Ethiopia is highly heterogeneous and comprises approximately 6027 species of higher plants, of which approximately 10% are endemic⁵. However, biodiversity is under severe threat from anthropogenic pressures⁶. Many endemic species are critically endangered⁷. Conservation efforts by various organizations have achieved some success⁸; for example, the Walia ibex in the SMNP has improved from critically endangered to endangered, and site-specific enclosures have facilitated vegetation recovery. Such success demonstrates that active conservation can revive biodiversity; however, these measures alone remain insufficient against ongoing threats^6,8.

The Simien Mountains National Park (SMNP), located on the northern edge of the Simien Mountains massif, was inscribed as a UNESCO World Heritage Site in 1978 because of its exceptional biophysical features and rich biodiversity⁹. Understanding vegetation ecology is essential for biodiversity conservation; although numerous studies have examined the park^10–16, information on biodiversity metrics and how environmental variables shape plant community formation and species distribution remains limited.

The park faces anthropogenic pressures, including land degradation and habitat fragmentation, leading to reduced forest cover, mainly in inaccessible areas¹⁷. Sub-Afroalpine and Afroalpine vegetation has lost much of its natural structure and ecological function, affecting wildlife habitats such as those of the red fox⁹. Previous studies^18,19 have been largely descriptive, focusing on species inventories without quantifying diversity metrics or analyzing soil-vegetation interactions, leaving a clear research gap. Therefore, this study aimed to (i) quantify plant community structure using established biodiversity indices, (ii) analyze how soil variables influence vegetation patterns, and (iii) provide evidence to guide site-specific conservation strategies. These objectives directly address the knowledge gap by moving from descriptive inventories to analytical ecological assessments.

Materials and methods

Descriptions of the study area

The study was conducted in SMNP, located on the northern periphery of the Simien Mountains massif in northern Ethiopia. The park lies approximately 857 km north of Addis Ababa and 120 km northeast of Gondar city, within the Amhara Regional State. SMNP was established in 1966 and currently covers an area of approximately 412 km²²⁰. It lies within five districts, namely Debark, Adiarkay, Janamora, Beyeda, and Tellemit, and shares borders with 42 kebeles, stretching from 13 °06’ 44.09’’ to 13⁰ 23’ 07.85’’ N latitude and from 37⁰ 51’ 26.36’’ to 38⁰ 29’ 27.59’’ E longitude (Fig. 1). The Simien Mountains constitute the highest regions of the Ethiopian Plateau (4,550 m a.s.l.)^18,19. The park’s unique landscapes and high biodiversity, with endemic species, led to its designation as a UNESCO World Heritage Site in 1978 (SMNP Office report, 2020).

Fig. 1.

Map of the study area showing study sites and plots by Getinet.

(source: ArcGIS version 10.8; URL: http://my.esri.com/).

The mountain range topography resulted from uplift and basaltic lava extrusions during the late Mesozoic to early Tertiary, followed by erosion, creating cliffs, canyons, gorges, and rugged peaks (Fig. 2). Climate varies with altitude; analyses from the Debark (1964–2023) and Chenek (2007–2023) stations indicate a unimodal rainfall pattern, with 75% of the annual precipitation occurring between June and August (Fig. 3). Temperatures ranged from 6.3 to 22.7 °C in Debark and 2.3–16.8 °C in Chenek.

Fig. 2.

Major landform types of the Simien Mountains by Getinet Masresha.

(source: ArcGIS version 10.8; URL: http://my.esri.com/).

Fig. 3.

SMNP climate diagrams for Debark and Chenek stations.

Vegetation is classified into four zones: Afroalpine, ericaceous belt, Afromontane, and woodland (Fig. 4). The Afromontane zone (2,000–3,000 m a.s.l.) represents less steep escarpments and contains remnant forest patches dominated by Prunus africana, Apodytes dimidiata, Olea europaea subsp. cuspidata, and Pittosporum viridiflorum, with a sparse herb layer due to grazing and human disturbance¹⁸.

Fig. 4.

Vertical zonation of Simien Mountain’s vegetation by Getinet Masresha.

(source: ArcGIS version 10.8; URL: http://my.esri.com/).

Study design and sampling

After a reconnaissance survey, a stratified systematic sampling design was applied to account for the heterogeneity in vegetation across the study area. Sampling intensity was proportional to local floristic diversity: areas with higher diversity and rapid changes in cover received more plots, while homogeneous areas received fewer plots²¹. A total of 139 main plots (20 × 20 m) were distributed across four representative Afromontane forest patches (Adarmaz, Muchila, Limalimo, and Debir-Sankaber). Within each main plot, five 2 × 2 m subplots (four corners and one center) were established to capture fine-scale herbaceous and juvenile woody species data. Species identity and percentage cover of adult woody plants were recorded in main plots. The cover of herbaceous species recorded in subplots was extrapolated to the main plot by multiplying subplot cover values by the proportion of subplot area to main plot area, and then standardized using Braun-Blanquet scales (1–9)²². This allows integration of fine-scale vegetation into plot-level analyses.

All plant specimens were collected with vernacular names and codes, identified at the National Herbarium of Ethiopia (ETH) following standard herbarium protocols using the Flora of Ethiopia and Eritrea (FEE) and cross-referenced with authenticated ETH specimens. Scientific names were verified using the World Flora Online database (https://wfoplantlist.org/), and voucher specimens were curated at ETH.

From each subplot, five soil cores (0–30 cm depth, three 10 cm layers) were composited into one representative sample per main plot. Soil variables were selected for their influence on nutrient availability, water retention, and plant growth, which are key determinants of vegetation patterns. Soil analyses included pH, texture, organic matter, total nitrogen, available phosphorus, exchangeable potassium, electrical conductivity, and cation exchange capacity, following standard procedures²³. Terrain variables (altitude, slope, aspect, and coordinates) were measured at plot centers using GPS, clinometer, and compass. Aspect values were codified for software integration (N = 0, NE = 1, E = 2, SE = 3, S = 4, SW = 3.3, W = 2.5, NW = 1.3)²⁴.

Data analyses

Florestic composition and plant community classification

Floristic composition was analyzed using descriptive statistics. Hierarchical cluster analysis (R 4.3.3) with similarity ratio and Ward’s method identified distinct plant communities. The optimal number of clusters was determined using the Elbow method²⁵. Synoptic tables summarized species occurrences, with synoptic-cover abundance values calculated as the product of species frequency and mean cover²⁶.

Diversity indices

Species diversity was quantified using Shannon–Wiener (H′) for species richness and relative abundance, while Pielou’s evenness (J) measured species distribution uniformity, allowing meaningful comparisons among communities.

Where S = total number of species, Pi = proportion of individuals of species i, ln stands for the natural logarithm, and Hmax′ = maximum diversity. Shannon-Wiener was preferred for its robustness to sample size and ability to weight rare and common species.

Species richness Estimation

Non-parametric species richness estimators (ACE, Chao1, Chao2, Jackknife 1, Jackknife 2, and Bootstrap) were applied to quadrat-based data to estimate total species richness, as they do not rely on parametric abundance models^27,28. Species richness was computed in EstimateS v 9.1.0²⁹, with sample order randomized 100 times to obtain mean estimates across accumulation levels.

Comparisons of species composition among communities

Jaccard’s Similarity Index and β-diversity quantified floristic similarity and turnover between communities^30,31.

Ordination of vegetation environmental data

Preliminary DCA indicated a gradient length of 4.6, supporting a unimodal model^22,32. Canonical correspondence analysis (CCA) was then performed to examine relationships between vegetation composition and environmental variables. Nine significant environmental variables were selected using Monte Carlo permutation tests and the Adonis function. The variation explained by the first four CCA axes was considered in subsequent analyses.

Results

Floristic composition

The floristic analyses of the entire study area yielded a total of 354 species distributed across 255 genera and 91 families. Three hundred fifty-one plant specimens were identified at the species level, while the remaining three were identified at the subspecies level. This total included eight pteridophytes, one gymnosperm, and 82 angiosperms (15 monocotyledons and 67 dicotyledons) families. In the study area, 10 ferns, 1 gymnosperm, 292 dicot, and 51 monocot species were recorded (Supplementary material).

The most species-rich families were Asteraceae (16%; 33 genera, 56 species), Poaceae (6%; 16 genera, 23 species), Fabaceae (6%; 17 genera, 22 species), Lamiaceae (5%; 10 genera, 18 species), and Rubiaceae (4%; 9 genera, 15 species) (Fig. 5). Collectively, these five families accounted for 37% of the total recorded species. Nine additional families contained between 7 and 10 species each, while the remaining 77 families were species-poor, each contributing 1–6 species and together accounting for 41% of the flora. This pattern indicates a floristic structure characterized by dominance of a few species-rich families and a large number of families with low species representation.

Fig. 5.

Percent species contribution of families.

Regarding growth forms, herbs dominated 61.86% (219 species), followed by woody species 38.14% (135 species: 50 trees, 56 shrubs, 29 lianas). Among the herbs, 14 were ferns and two epiphytic species. Notably, 13 species were new records for the Gondar floristic region (1 tree, 4 shrubs, 8 herbs; Table 1), reflecting gaps in previous floristic documentation rather than recent colonization.

Table 1.

New vascular plants recorded from the Gondar floristic region in the FEE.

No	Species	Family	Habit
1	Acanthopale aethio-germanica	Acanthaceae	Shrub
2	Achyrospermum schimperi	Lamiaceae	Herb
3	Acmella caulirhiza	Asteraceae	Herb
4	Commelina benghalensis	Commelinaceae	Herb
5	Conyza spinosa	Asteraceae	Shrub
6	Erica trimera	Ericaceae	Tree
7	Gomphocarpus fruticosus	Asclepiadaceae	Shrub
8	Isoglossa punctata	Acanthaceae	Herb
9	Misopates orontium	Scrophulariaceae	Herb
10	Momordica pterocarpa	Cucurbitaceae	Herb
11	Oplismenus burmannii	Poaceae	Herb
12	Pilea tetraphylla	Urticaceae	Herb
13	Psychotria orophila	Rubiaceae	Shrub

Endemism and conservation status showed that 45 species (12.71%) were endemic to Ethiopia, seven of which were strictly endemic to SMNP (Table 2). Endemic species were predominantly herbs (62.22%), followed by shrubs (26.67%), lianas (6.67%), and trees (4.44%), with Asteraceae accounting for 40% of endemic taxa.

Table 2.

List of endemic species in the Afromontane portion of SMNP vegetation.

No	Species	Family	Habit	Status
1	Argyrolobium schimperianum	Fabaceae	Shrub	EN
2	Bidens pachyloma	Asteraceae	Herb	LC
3	Carduus macracanthus	Asteraceae	Herb	LC
4	Centrus nanus	Poaceae	Herb	VU
5	Ceropegia sobolifera*	Asclepiadaceae	Climber	CR
6	Chiliocephalum schimperi	Asteraceae	Herb	NT
7	Clematis longicauda	Ranunculaceae	Climber	LC
8	Conyza spinosa	Asteraceae	Shrub	VU
9	Crassocephalum macropappum	Asteraceae	Herb	LC
10	Crepis tenerrima	Asteraceae	Herb	EN
11	Crepis xylorrhiza *	Asteraceae	Herb	CR
12	Cussonia ostinii	Araliaceae	Tree	NT
13	Cynoglossum zeylanicum	Boraginaceae	Herb	LC
14	Echinops longisetus	Asteraceae	Shrub	LC
15	Festuca macrophylla	Poaceae	Herb	VU
16	Gymnanthemum myrianthum	Asteraceae	Shrub	VU
17	Habenaria platyanthera *	Orchidaceae	Herb	CR
18	Herniaria abyssinica	Caryophylaceae	Herb	EN
19	Impatiens tinctoria	Balsaminaceae	Herb	LC
20	Laggera tomentosa	Asteraceae	Herb	LC
21	Leucas stachydiformis	Lamiaceae	Shrub	NT
22	Mikaniopsis clematoides	Asteraceae	Climber	LC
23	Millettia ferruginea	Fabaceae	Tree	LC
24	Otostegia tomentosa subsp. steudneri	Lamiaceae	Shrub	VU
25	Pentameris trisetoides	Poaceae	Herb	NT
26	Peucedanum petitianum	Apiaceae	Herb	LC
27	Phragmanthera macrosolen	Loranthaceae	Shrub	LC
28	Pimpinella pimpinelloides *	Apiaceae	Herb	CR
29	Plectranthus garckeanus	Lamiaceae	Herb	LC
30	Pseudognaphalium melanosphaerum	Asteraceae	Herb	VU
31	Sagina abyssinica subsp. abyssinica	Caryophylaceae	Herb	NT
32	Saxifraga hederifolia	Saxifragaceae	Herb	LC
33	Senecio farinaceous	Asteraceae	Herb	EN
34	Senecio fresenii	Asteraceae	Herb	NT
35	Senecio myriocephalus	Asteraceae	Shrub	LC
36	Senecio unionis	Asteraceae	Herb	VU
37	Snowdenia mutica *	Poaceae	Herb	CR
38	Solanecio gigas	Asteraceae	Shrub	LC
39	Solanum macracanthum	Solanaceae	Shrub	LC
40	Solanum hirtulum	Solanaceae	Herb	LC
41	Solanum marginatum*	Solanaceae	Shrub	LC
42	Sonchus melanolepis	Asteraceae	Herb	VU
43	Thalictrum minus subsp. maxwellii	Ranunculaceae	Herb	NT
44	Verbascum benthamianum *	Scrophulariaceae	Shrub	LC
45	Verbascum stelurum	Scrophulariaceae	Herb	VU

Taxa endemic to SMNP are indicated by asterisk (*). EN = Endangered, LC = Least concerned, NT = Near threatened, VU = Vulnerable, CR = Critically endangered.

Overall, the results indicate a relatively high floristic richness with a notable contribution of endemic species; however, these findings are limited to the sampled plots and may not fully capture the entire floristic variability of SMNP.

Community types in the Afromontane vegetation

Cluster analysis of 139 plots containing 354 species identified four distinct plant communities, as determined by the elbow method (Fig. 6) and validated through hierarchical clustering (Fig. 7). The communities varied in size, ranging from 12 to 40 plots (Table 3), and were named according to their dominant species (Table 4).

Fig. 6.

Optimal number of clusters by elbow method.

Fig. 7.

Hierarchical cluster analysis for Afromontane vegetation in SMNP.

Table 3.

Altitudinal range and plots of each community type.

Community type	Altitudinal range	Number of plots	Plots in the community
Adarmaz	2244–2758	37	1–4, 6, 7, 9, 10, 14–19, 21–32, 34–40, 46, 70, 89, 134
Muchila	2469–3065	40	11,13, 41–43, 47–69, 71, 73, 75–80, 84, 85, 113, 133
Limalimo	2658–2905	27	81–83, 86–88, 90–95, 97–99, 101–105, 108, 109, 112, 120, 135–138
Sankaber	2895–3150	12	114–117, 119, 124, 127–132

Table 4.

Synoptic abundance value for a species having a value of ≥ 1 in at least one community type and values in bold refer to dominant species.

Species	Adarmaz	Muchila	Limalimo	Debir-Sankaber
Euphorbia ampliphylla	3.89	0.53	0.14	0
Olea capensis subsp. macrocarpa	3.81	0.53	0.11	0
Calpurnia aurea	3.14	0.33	0.39	0
Hypoestes forskaolii	3.03	1.28	0.86	0
Clausena anisata	2.46	1.2	0.14	0
Clutia abyssinica	2.41	1.65	0.39	0.17
Olea europaea subsp.cuspidata	2.27	0.73	0.75	0.17
Apodytes dimidiata	2.16	0.78	1.71	0
Impatiens hochstetteri	2.14	0.25	0.11	0
Achyrospermum schimperi	1.76	0.03	0.14	0
Girardinia bullosa	1.46	0	0	0
Carissa spinarum	1.41	0.15	0.36	0
Myrsine melanophloeos	0.16	4.10	0.57	0.92
Myrica salicifolia	2.54	3.50	1.96	0
Myrsine africana	3.16	3.46	3.05	0.53
Jasminum abyssinicum	2.57	3.44	1.11	3.22
Clematis simensis	2.6	3.41	2.37	1.74
Selaginella goudotiana	2.91	3.41	2.71	0
Cyperus fischerianus	0.57	3.11	0	0.17
Nuxia congesta	1.51	2.88	1.43	0
Geranium arabicum	0.89	2.88	2.54	2.75
Koordersiochoa longiarista	1.3	2.60	1.82	0.17
Adiantum poiretii	1.43	2.48	1.64	0.17
Asparagus africanus	0.16	2.43	1.11	1.08
Alchemilla cryptantha	0.97	2.25	0.82	1.75
Osyris lanceolata	1.14	2.20	1.21	0.08
Bersama abyssinica	2.05	2.13	1.29	0
Rosa abyssinica	0.49	2.08	1.21	0.83
Erica trimera	0.19	1.75	0.43	0
Galium spurium	0.3	1.58	0.07	0.17
Hypoestes triflora	1.22	1.45	1.36	0
Veronica abyssinica	0.03	1.33	0.36	0.58
Crassocephalum macropappum	0.35	1.23	0.64	1.5
Gymnosporia arbutifolia	2.73	2.23	3.64	1.5
Pittosporum viridiflorum	0.43	2.78	3.07	0.17
Pavetta abyssinica	3.15	3.41	3.06	0.26
Justicia ladanoides	0.7	0.65	2.82	0.25
Vernonia rueppellii	1.65	1.63	2.25	0
Dombeya torrida	1.65	1.7	1.96	0
Dovyalis abyssinica	1.03	1.4	1.96	0
Brucea antidysenterica	1.41	0.4	1.79	0
Allophylus abyssinicus	0.51	0.4	1.79	0
Galiniera saxifraga	0.19	1.13	1.54	0
Mikaniopsis clematoides	0.11	0.45	1.5	0.17
Sanicula elata	0.27	0.4	1.5	0.17
Achyranthes aspera	0.57	1.25	1.36	1.33
Scepocarpus hypselodendron	0.95	1.15	1.32	0.08
Tacazzea conferta	0	0	1.25	0
Trifolium semipilosum	0.57	0.3	1.11	0.92
Erica trimera	0	0.75	0.11	3.81
Cynoglossum amplifolium	0.03	0.9	0.64	3.67
Tenaxia subulata	0	0	0.07	2.75
Anthriscus sylvestris	0	0	0.18	2.67
Rumex nepalensis	0.05	0.15	0.43	2.5
Zehneria scabra	0.22	0.7	0.5	1.92
Cerastium lanceolatum	0.14	0.28	0.57	1.83
Cynoglossum zeylanicum	0.27	0.45	0.54	1.75
Pentameris trisetoides	0	0	0.04	1.67
Lactuca inermis	0.03	0.15	0.07	1.58
Arabis alpina	0	0	0	1.58
Andropogon lima	0	0	0.18	1.50
Senecio myriocephalus	0	0.1	0.04	1.33
Micromeria imbricata	0.14	0.05	0.54	1.25
Thymus schimperi	0	0.18	0.07	1.17
Andropogon amethystinus	0	0	0.18	1.08
Pterocephalus frutescens	0	0	0.04	1.08

1. Euphorbia ampliphylla – Olea capensis subsp. macrocarpa: 37 plots, 142 species, altitude 2244–2758 m, steep northeast-facing slopes (avg. 27.8%). Dominant trees/shrubs: Myrica salicifolia, Clausena anisata, Olea europaea subsp. cuspidata; dominant herbs: Hypoestes forskaolii, Selaginella goudotiana.

2. Myrsine melanophloeos – Myrica salicifolia: 40 plots, 165 species, altitude 2469–3065 m, steep slopes (avg. 33.3%). Dominant trees/shrubs: Myrsine africana, Pavetta abyssinica, Nuxia congesta; ground flora: Selaginella goudotiana, Cyperus fischerianus.

3. Gymnosporia arbutifolia – Pittosporum viridiflorum: 27 plots, 148 species, altitude 2658–2905 m, medium slopes (avg. 20.9%). Dominant trees: Gymnosporia arbutifolia, Pittosporum viridiflorum; dominant herbs: Justicia ladanoides.

4. Erica trimera – Cynoglossum amplifolium: 12 plots, 92 species, altitude 2895–3150 m, gentle to medium slopes (avg. 20.1%). Dominant tree/shrub: Myrsine melanophloeos; herbaceous layer: Cynoglossum amplifolium, Geranium arabicum.

In conclusion, these communities represent distinct assemblages along altitudinal and topographic gradients, although some species overlap occurs among community types.

Comparisons of species diversity among communities in Afromontane vegetation

Diversity indices varied among communities (Table 5). Fisher’s α was lowest in Debir-Sankaber (25.4) and highest in Muchila (35.1). Shannon diversity ranged from 4.03 (Debir-Sankaber) to 4.50 (Muchila), and evenness from 0.87 (Adarmaz) to 0.89 (Debir-Sankaber).

Table 5.

Shannon-Wiener diversity, fisher α diversity and richness of the communities.

Diversity indices	Adarmaz	Muchila	Limalimo	Debir- Sankaber
Shannon	4.32	4.50	4.38	4.03
Evenness	0.87	0.88	0.88	0.89
Fisher α	30.7	35.1	35.0	25.4
Richness	142	165	148	92
Rarefaction	169	203	187	120

In conclusion, the relatively small variation in diversity and evenness values suggests broadly comparable species distribution patterns among communities, despite differences in richness and environmental conditions.

Species richness Estimation

Nonparametric species richness estimators’ analyses revealed the total species richness and sampling effort (Table 6). Jackknife 2 yielded the highest estimates (168.6–203.3), while ACE provided the lowest (100.7–173.8). Observed species represented 79–96.9% of estimated richness, indicating substantial sampling completeness.

Table 6.

Number of samples, observed species and estimated species richness based on different estimators at the four forest patches.

Characteristics	Adarmaz	Muchila	Limalimo	Debir-Sankaber
No of samples	37	40	28	12
Sobs	142	165	148	92
ACE	148.5	173.8	155.2	100.7
Chao1	151.1	171.6	152.8	96.3
Chao2	154.5	184.3	166.5	104.4
Jacknife1	163.4	194.3	181.7	116.8
Jacknife2	168.6	203.3	187.4	120.3
Bootstrap	152.9	179.4	164.9	104.7
Species collection degree	84.2–94.0%	81.2–96.2%	79–96.9.9%	76.5–95.5%

In conclusion, these results suggest that sampling effort was generally adequate, although additional sampling could reveal further species, particularly in less-sampled communities such as Debir-Sankaber.

Comparisons of species composition similarity among communities

Jaccard similarity and β-diversity analyses revealed moderate to low floristic similarity among the Afromontane plant communities, with Jaccard similarity indices ranging from 0.28 to 0.64 and corresponding β-diversity values ranging from 0.22 to 0.39 (Table 7). The lowest similarity was observed between the Adarmaz and Debir-Sankaber communities (J = 0.28), indicating pronounced species turnover, whereas the highest similarity occurred between Adarmaz and Muchila (J = 0.64), reflecting a greater overlap in species composition. Overall, lower similarity values were consistently associated with higher β-diversity, highlighting substantial species turnover along environmental gradients across the study area.

Table 7.

Comparisons of floristic composition among afromontane communities.

Community	Adarmaz	Muchila	Limalimo	Debir-Sankaber
Adarmaz	1.00	0.64	0.58	0.28
Muchila	0.22	1.00	0.63	038
Limalimo	0.26	0.22	1.00	0.44
Debir-Sankaber	0.57	0.46	0.39	1.00

*Values in bold indicate Jaccard (J) similarity index and values in italics indicate β-diversity index.

Ordination of vegetation and environmental variables

Canonical Correspondence Analysis (CCA) revealed the environmental gradients shaping plant distribution in SMNP’s Afromontane vegetation. Detrended Correspondence Analysis (DCA) indicated high β-diversity (axis length = 4.6426), reflecting substantial heterogeneity among communities (Table 8).

Table 8.

DCA result showing the heterogeneity of vegetation composition.

DCA axes	DCA1	DCA2	DCA3	DCA4
Eigenvalues	0.5017	0.2434	0.1806	0.1538
Decorana values	0.5292	0.2360	0.1729	0.1575
Axis lengths	4.6426	2.6252	2.4527	3.6305

Nine environmental variables significantly influenced species distribution (Table 9). Based on CCA (Table 10), altitude was the primary driver, strongly correlated with axis 1 (0.977), followed by pH (−0.580), phosphorus (AP, −0.176), total nitrogen (−0.295), and electrical conductivity (−0.364). Axis-1 explained 41% of variation, axis-2 (16%), axis-3 (10%), and axis-4 (8.8%), with the cumulative variation explained by the first four axes being 75.8%. Axis-1 captured most variation in species composition, primarily influenced by altitude and soil chemistry, whereas axis-2 was mainly affected by organic matter and slope.

Table 9.

Result of function adonis test of environmental variables.

Variable	Df	Sum of Squares	Mean of Squares	F.Model	R 2	Pr (> F)
Altitude	1	3.8288	3.8288	18.9955	0.15795	0.01 **
Slope	1	0.9100	0.9100	4.5147	0.03754	0.01 **
AP	1	0.5439	0.5439	2.6986	0.02244	0.01 **
CEC	1	1.2449	1.2449	6.1765	0.05136	0.01 **
K	1	0.5318	0.5318	2.6384	0.02194	0.02 *
OM	1	0.4491	0.4491	2.2282	0.01853	0.01 **
pH	1	0.5699	0.5699	2.8274	0.02351	0.01 **
EC	1	0.4403	0.4403	2.1845	0.01817	0.03 *
Clay	1	0.2208	0.2208	1.0956	0.00911	0.29
Sand	1	0.2809	0.2809	1.3938	0.01159	0.12
TN	1	0.6286	0.6286	3.1189	0.02593	0.02 *
Aspect	1	0.2795	0.2795	1.3868	0.01153	0.11
Residuals	71	14.3109	0.2016		0.59039
Total	83	24.2395			1.00000

Significant environmental variables are indicated by asterix at their P-value, DF = degree of freedom, Pr = probability, F. = F test model, R² = Coefficient of determination.

Table 10.

Biplot scores for constraining variables and their correlation with the CCA axes,.

Factor	CCA1	CCA2	CCA3	CCA4
Altitude	0.977	0.10	0.107	0.091
Slope	−0.047	0.40	−0.754	0.365
AP	−0.176	−0.45	−0.019	0.290
K	−0.168	0.15	0.478	0.212
OM	0.185	−0.82	−0.116	0.180
EC	−0.364	−0.39	−0.406	−0.315
CEC	−0.060	−0.33	−0.300	0.366
TN	−0.295	−0.42	−0.377	0.017
pH	−0.580	0.22	0.017	0.415
Eigenvalue	0.47	0.18	0.12	0.089
Prop. explained	0.41	0.16	0.10	0.088
Cumulative Percentage	0.41	0.57	0.67	0.758

The CCA ordination diagram (Fig. 8) illustrates the spatial segregation of forest patches: Muchila plots cluster in Quadrant I, Limalimo in Quadrant II, Adarmaz in Quadrant III, and Debir-Sankaber in Quadrant IV. Environmental gradients such as phosphorus, organic matter, total nitrogen, electrical conductivity, and cation exchange capacity strongly influenced species distribution in Adarmaz. Slope and altitude shaped the composition in Muchila, while pH, slope, altitude, and potassium affected Limalimo. Debir-Sankaber species distribution was primarily driven by altitude and organic matter.

Fig. 8.

CCA Ordination diagram of plots with environmental variables biplot.

Overall, altitude emerged as the strongest environmental correlate of species composition within the sampled plots, while soil chemical properties and slope also contributed to community differentiation.

Discussion

Floristic composition

This study documented 354 vascular plant species in the Afromontane vegetation of SMNP, confirming the region’s high floristic richness. This diversity reflects the park’s complex topography deep gorges escarpments, ridges and plateaus which generates a mosaic of microhabitats supporting diverse species assemblages⁴. Compared with other Ethiopian highlands, SMNP is richer than Abune Yosef (199 species)³² and Arsi Mountains National Park (191 species)³³, but less diverse than the more extensive Bale Mountains (1321 species)³⁴ and Mount Kilimanjaro (1200 species)³⁵. These contrasts likely arise from differences in elevation range, geographic area, biogeographic history and survey intensity³⁶.

Asteraceae, Poaceae and Fabaceae were the most species-rich families, consistent with patterns from other Ethiopian highlands^32,33 and previous studies in SMNP^17,36. Their success is attributable to ecological adaptability and dispersal mechanisms; for example, many Asteraceae and Poaceae possess wind-dispersed diaspores suited to colonizing isolated montane habitats, while Fabaceae benefit from nitrogen-fixing associations and allelopathic traits that enhance establishment in nutrient-poor soils^37–41.

Herbs dominated the flora, as commonly observed in Afromontane systems where herbaceous species exhibit traits that enable survival under variable climatic conditions³⁷. Thirteen taxa recorded in this survey are new to the Gondar floristic region, adding to the 19 previously reported¹⁷, and underscoring that remote, topographically challenging areas of SMNP remain under-sampled^17,35.

Sampling limitations include difficult terrain, single-season sampling, and human disturbances, which likely led to underrepresentation of rare, cryptic, or seasonally ephemeral species and underscore the need for multi-season surveys in remote areas. Despite these constraints, the high species richness and new records highlight the conservation importance of the Simien Mountains, where protecting vulnerable habitats and integrating floristic data into management plans are essential to prevent local extinctions.

Species Diversity, distribution and endemism

Four distinct plant community types were identified; each structured by topography and disturbance gradients. Community 2 (Muchila patch) exhibited the highest species richness and diversity, likely due to intermediate disturbance, broad altitudinal range and moisture-retaining north-facing slopes³⁶. Community 3 (Limalimo forest patch) ranked second, reflecting improved protection following the park’s expansion. Community 1 (Adarmaz patch) appeared to represent a later successional stage with relatively lower diversity⁴². Community 4 (Debir–Sankaber), located near the ericaceous belt at the highest elevations, had the lowest richness, consistent with the well-documented decline of diversity at higher altitudes⁴³.

Beta diversity was greatest between the lowest (Adarmaz) and highest (Debir–Sankaber) communities, highlighting the strong influence of altitude on species turnover. Muchila, spanning the widest altitudinal range, shared the most species with other communities.

Endemism accounted for 12.2% (45 taxa) of the flora, including seven species restricted to the Afromontane portion of SMNP. This level is comparable to other Ethiopian highlands (10–15%)^17,44–46 and reflects the role of the Simiens’ isolated plateaus and escarpments in promoting speciation^47,48. Many endemic species are herbaceous and therefore vulnerable to grazing and trampling, underscoring the need for targeted conservation of these microhabitats.

Environmental drivers of vegetation patterns

Canonical Correspondence Analysis (CCA) revealed that altitude is the dominant environmental gradient shaping species distribution, strongly correlating with the first axis. Altitude integrates changes in temperature, moisture and soil conditions, all of which influence plant establishment and growth^49–51. Slope aspect and angle also played significant roles, with north- and northwest-facing slopes supporting richer vegetation due to greater moisture retention ^[36]. Steeper slopes influence soil formation, erosion and microclimate, contributing to variation in community composition^52–54.

A key result is the clear imprint of historical human disturbance on present vegetation. Forest patches are now largely confined to inaccessible escarpments and gorges, indicating extensive past fragmentation. The absence of characteristic dry Afromontane trees such as Juniperus procera from forest stands now found mainly in churchyards further reflects historical deforestation and vegetation replacement. Although anthropogenic pressure has decreased since the area’s designation as a national park, ongoing disturbances such as controlled grazing, beekeeping and edge effects continue to influence vegetation structure and species turnover^55–58.

Management implications

SMNP supports substantial Afromontane biodiversity with high levels of endemism. The protection regime implemented after 1991, limiting agricultural expansion and large-scale logging, has likely contributed to observed recovery and enhanced plant diversity in many areas^59,60. Nevertheless, several management priorities emerge from this study:

1. Protection of inaccessible habitats: Remaining forest patches on cliffs and in deep gorges serve as natural refugia. Any development increasing access to these areas should be carefully evaluated to avoid unintended degradation.

2. Targeted conservation of endemics: Endemic and rare herbaceous species are particularly vulnerable to grazing and localized disturbances. Microhabitats supporting these taxa may require enhanced protection or complementary ex-situ measures.

3. Managing disturbance regimes: Intermediate disturbance appears to promote diversity in some areas. Management should maintain a mosaic of disturbance levels, ensuring strict protection of core refugia (e.g., Walia ibex habitats) while allowing sustainable traditional practices in buffer zones.

4. Addressing knowledge gaps: Continued discovery of previously unrecorded taxa highlights the need for further botanical exploration, especially in rugged, under-sampled terrain. Establishing long-term monitoring plots is recommended to track vegetation change under climate and management pressures.

Conclusions and recommendations

The Afromontane vegetation of SMNP exhibits substantial floristic richness, with 354 recorded species across 91 families, including 45 Ethiopian endemic species, seven of which are restricted to the park. This diversity is associated with pronounced altitudinal variation, topographic complexity, and heterogeneity in environmental conditions within the sampled plots, as reflected by the observed community differentiation and high species turnover.

This study quantified plant community composition and diversity patterns and examined their relationships with selected environmental variables, revealing that altitude, together with soil properties and slope, was strongly correlated with variation in species composition. The high β-diversity observed among communities indicates considerable spatial heterogeneity in species assemblages across forest patches. However, these patterns represent correlations based on the sampled data and do not imply direct causal relationships.

Despite evidence of past deforestation and ongoing anthropogenic pressures reported in previous studies, the results indicate that SMNP continues to support important reservoirs of Afromontane plant diversity, including endemic and conservation-priority taxa. Nevertheless, the findings are constrained by plot-based sampling and may not capture the full floristic variability of the park, particularly in less accessible areas.

From a management perspective, conservation efforts may benefit from prioritizing habitats that support high endemic richness and distinct community assemblages, particularly along altitudinal gradients. Continued botanical surveys, expanded spatial coverage, and long-term vegetation monitoring are recommended to improve understanding of temporal dynamics and disturbance responses. Integrating ecological information into site-specific management and conservation planning, together with stakeholder and community engagement, could contribute to the sustained conservation of SMNP’s plant biodiversity.

Supplementary Information

Below is the link to the electronic supplementary material.

Author contributions

G.M: Conceptualization, Field Data Collection, Data Analysis, Investigation, Laboratory Work, Manuscript Drafting; T.S: Supervision, Reviewing and Editing; M.W: Supervision, Reviewing and Editing, M.A: Conceptualization, Methodological Design, and Editing; and D.T: Reviewing and Editing; and W.M: Conceptualization and Editing and Prepared the Reference and Citation Following the Journal Style.

Data availability

Data is provided within the manuscript or Supplementary Materia.

Declarations

Competing interests

The authors declare no competing interests.