How does topography affect plant communities

RDA was selected due to its better visualization of the graph. In this analysis, 86 sample plots, species and 10 environmental variables altitude, slope, bulk density, moisture content, clay, pH, EC, available Phosphorus, CEC, and OM were included.

Adonis test was performed to determine the significance of the environmental variables on plant community distribution. Consequently, RDA ordination was plotted using cover-abundance values of plant species and data of significant environmental variables. One-way ANOVA followed by post-hoc Tukey HSD test was used whether there were significant mean differences among plant communities about environmental variables, species richness, diversity and evenness.

A total of species, belonging to 80 families were recorded in the study area. Asteraceae and Fabaceae were the top most dominant families.

Of the total plant species composition of the forest, 18 Five plant community types were identified from the hierarchical cluster analysis in the study area Fig 3. The community is named after one or two dominant indicator tree or shrub species selected by the relative magnitude of their indicator values. Consequently, the identified communities were Erica arborea-Osyris quadripartita , Discopodium penninervium-Echinops pappii , Olea europaea subsp.

This community is found in the Shangi Derkie forest patch, which has a very steep slope. The altitudinal range of this community type lies between and ma. The community has six indicator species with significant indicator values, namely; Erica arborea , Osyris quadripartita , Bersama abyssinica , Buddleja polystachya , Maesa lanceolata , and Rosa abyssinica.

The tree layer was dominated by Ekebergia capensis and Lepidotrichilia volkensii. The shrub layer was dominated by Lippia adoensis. The most dominant species in the herb layer include Kniphofia foliosa , Kalanchoe petitiana , Verbascum sinaiticum and Trifolium decorum.

This community type is represented by species, being the richest in a number of species among the five community types. The altitudinal range of this community type lies between and m a. The indicator species are Discopodium penninervium , Echinops pappii and Laggera tomentosa. The most dominant shrub species were Solanecio gigas , Maytenus arbutifolia , Solanum incanum , Rumex nervosus , Gnidia glauca and Acanthus sennii. The tree layer was dominated by Arundinaria alpina.

Liana such species such as Asparagus africanus and Phytolacca dodecandra were dominant. The herb layer was dominated by Plectranthus assurgens and Carduus schimperi. This community is comprised of species. This community lies between altitudes and m above sea level. Similar to community 1 and 2, Olea europaea subsp. The indicator tree and shrub species of this community are Olea europaea subsp. The dominant species in the tree layer include Apodytes dimidiata. The shrub species such as Rhus glutinosa , subsp.

The herb layer comprised of Oplismenus hirtellus , Impatiens hochstetteri , Impatiens rothii and Justicia heterocarpa. This community is comprised of 73 species. This community type is located between altitudes and m asl, and which is found in 3 forest patches: Bunise, Shangi Derkie, Aradie, and Masikana.

The indicator species are Euphorbia abyssinica and Prunus africana. The shrub layer includes Solanecio gigas and liana species Embelia schimperi were also dominant. The herb layer was dominated by Hypoestes forskaolii. It consists of 84 species. Community 5 found in the Samana forest patch. This community is established at lower elevations — m a. Dodonaea anguistifolia and Acokanthera schimperi are the characteristic species of the shrub, and tree layers, respectively. Other dominant tree species include Croton macrostachyus , Acacia seyal , and Combretum molle.

The shrub layer was dominated by Euclea schimperi. Dominant species of the herb layer were Bidens macroptera and Satureja abyssinica. On the other hand, community 4 had the highest evenness value followed by communities 3 and 5. Community 1 and 2 had the least evenness value Table 4. Results of plant community similarity indicated that communities 2 and 3, communities 1 and 2, communities 1 and 3 have the same similarity index values. The least similarity was between community 1 and 5, community 3 and 5, community 4 and 5 Table 5.

Altitude was positively correlated with moisture content, nitrogen and sand are negatively correlated with pH and bulk density. Nitrogen and phosphorus are positively correlated with soil moisture content and organic matter.

CEC is positively correlated with organic matter, nitrogen and phosphorus. Soil pH shows a positive correlation with phosphorus while EC shows a positive correlation with organic matter see Table 6. We described several of these variables are significant but none of them account for much variability except elevation. A high sum of squeres would indicate a lot of variability in the data, while a low sum of squeres most of the measurement close to mean would indicate a low amount of variability Table 7.

The RDA diagram indicated that the first axis was primarily correlated with elevation, clay, and moisture content, while the second axis was correlated with P, OM and moisture content Fig 4 , Table 8. The eigenvalue for the first and second axis were 0.

The first axis eigenvalue which closer to 1 and show distribution of the plant communities along the axis is good. The arrows in the diagram stand for the environmental factors, the length of each arrow indicates the contribution of the factor to ordination axes, The numbers refer to quadrat number, and the angle between the arrows and he axes indicates the correlation between the variable and the ordination axe.

Consequently, the first two axes are sufficient to reflect the relationship between species and environmental factors. In the first RDA axis, elevation was the most important variable and separated communities at high elevation communities 1, 2, 3, and 4 from communities distributed at lower elevation communities 5 on the ordination axis Fig 4. On the other hand, in the second axis, communities 2 and 3 were located on sites with higher organic matter and moisture content.

The values of the different environmental variables average for each plant community type are presented in Table 9. We found relatively high plant species richness in Dega Damot district forest patches. However, the study area is fewer species-rich, especially in woody species than similar studies conducted in the Afromontane forest in Ethiopia, e.

Tara Gedam and Abebaye forests [ 45 ], Afromontane forest patches of Awi zone [ 46 ] It has higher species richness than other dry Afromontane forests in Ethiopia such as the Zengena forest [ 47 ], Kuandisha forest [ 48 ], and Amoro forest [ 26 ]. Besides, the number of woody species recorded in this study is more or less similar to that of the Zege Peninsula forest [ 49 ] whereas [ 50 ] recorded low woody species in the vegetation of Kalfou forest reserve, Cameroon.

The difference in species composition among the different areas is due to the number of plots sampled and its size can somehow explain this heterogeneity of the species richness. Thus, the present study suggests that the Dega Damot district had relatively high species composition, compared to other similar vegetation types in Ethiopia. The dominance of Asteraceae was reported from other studies in dry evergreen Afromontane forests vegetation type [ 23 , 52 , 53 ].

The dominance of Asteraceae in the present study may indicate that the forest patches might have been under a certain level of disturbances. As reported by [ 55 ] and [ 54 ], Asteraceae usually have a preference for open and disturbed lands to grow. Similarly, the results from the study area showed that relatively high endemicity Ethiopia is one of the centers of plant endemism in East Africa [ 57 ].

This study is in line with the typical feature of Afromontane forests that house numerous endemic species [ 58 ]. However, the Ethiopian Afromontane forests are one of the most degraded forests and continuously shrinking mainly due to anthropogenic disturbances [ 59 , 60 ]. Based on the hierarchical cluster analysis result, 5 plant communities were identified in the study area.

However, the location of the 3 community types community 2, 3, and 4 had overlapping ranges of elevation. Elevation represents a complex gradient combination of many different environmental factors such as topography, soil, moisture and climate [ 59 ] So that it is difficult to separate other environmental factors [ 61 ]. The vegetation of the area is classified as dry evergreen Afromontane forest and grassland complex DAF [ 28 ] and dominated by the species Olea europaea subsp.

The Olea europaea subsp. The identified plant communities are characterized by their different floristic composition. This could be attributed to variations in environmental factors. According to [ 62 , 63 ], the variation species composition among plant communities probably associated with the effects of environmental factors.

Nevertheless, species diversity and richness were not the same among plant communities. For instance, the highest species richness and diversity were recorded in community 1. On the contrary, community 5 had the least species richness and diversity than the remaining community types. The reason for high species diversity and richness of community 1 may be due to the highest altitudinal ranges in which this community is found — m. Also, community 5 type is the most disturbed community due to settlement, agricultural expansion, overgrazing by livestock and crossing road.

Anthropogenic land-use change is one of the most important factors contributing to global change [ 64 ], and changes in landscape structure and agricultural land-use intensity are likely to influence plant community composition and species richness. Changes in land-use practice may result in continuously or more abruptly deteriorating environmental conditions for some plant species, causing their decline in abundance and distribution [ 65 ].

For instance, over the last 31 years, the forest cover of Dega Damot district has decreased while areas under farmland, grazing, and settlements have increased [ 25 ]. Therefore, these anthropogenic land-use changes might influence the plant community formation of the present study in a different plant species richness and diversity.

These due to the location of this community have relatively similar environmental factors soil and altitudinal range.

Community 5 located at the lowest elevation with low content of organic matter, soil moisture content and which may have a less floristic similarity from the remaining plant community types Community 1, 2 and 3. The distribution of plant communities in the study area reflects the combined influence of altitude and soil factors. Based on the results of RDA, elevation was the major environmental variable in explaining variations in plant species distribution and patterns of plant community formation although there are overlaps among some community types.

This might be associated with a continuous change in environmental variables along the elevational gradient [ 63 , 66 ]. Other studies conducted in Ethiopia [see 18 , 23 , 67 ] also noted that altitude is the most important environmental variable for the determinant of vegetation variation. Moreover [ 68 ], reported that vegetation distribution influenced by elevation.

Besides, elevation is a vital environmental factor that affects the atmospheric pressure, moisture, and temperature which have a strong influence on the growth and development of plants and the distribution of vegetation [ 69 ].

Moreover, organic matter was also the most important constraining variable in plant community formation of the study area. Research in the Jibat forest, Ethiopia, by [ 19 ] reported that plant distributions were affected by the organic matter at a higher elevation.

SOM, its role in soil structure and moisture retention capability are well known [ 70 , 71 ]; these effects may account for its relevance for determining plant species distribution and community formation in the study area, besides its role as a source of soil nutrients to plants.

The mineralization of organic matter is a contributing factor in supplying available mineral nutrients for plant use and through decomposition process the available nitrogen. Similar to the present findings, nitrogen and P were also attributed to have significant effects on species compositions of plant communities in remnant Afromontane forests on the central plateau of Shewa [ 20 ].

Phosphorus is an essential nutrient for the growth of plant. This result is also in agreement with past similar works in in Afromontane and transitional rainforest vegetation of southwestern Ethiopia [ 67 ]. Furthermore, a study conducted in Brazil by [ 72 ], P was the main factor that distinct plant communities. Topographic features associated with soil properties are strongly correlated with species distribution and plant community structure on a local scale [ 33 ].

For instance, the Dodonaea anguistifolia-Acokanthera schimperi community, with a low content of organic matter, soil moisture content, and N, is differentiated from the other community types in the study area. The anthropogenic disturbances are higher at the lower altitudes selective cutting of trees, grazing by livestock and expanding of farmlands and the temperature is also higher at these altitudes. Generally, in the study area, the soil organic matter is higher at higher altitudes.

This might be due to the decreased decomposition of organic matter and the long-term accumulation of organic matter [ 73 ]. Much of the soil nitrogen is obtained from organic matter [ 74 ] and hence is bound in higher quantities at higher elevations. Five plant communities were identified from this study.

Among all of the investigated environmental factors, elevation, moisture content, slope, pH, EC, clay, OM, and phosphorus were found to significantly explain variation in species composition and community formation in the study area. Elevation was the most important environmental factor influencing species distribution and community formation.

The lower elevation resulted in a decline in species richness, diversity, organic matter, moisture content, especially in the community 5 in the forest. The anthropogenic disturbances present in this community type may also contribute to the low species richness and diversity recorded.

Also, Dodonaea anguistifolia-Acokanthera schimper i community type is not correlated to all the measured environmental variables. Therefore, it can be concluded that other environmental factors may influence the plant community formation, which is required to be additionally studied. The authors express their deepest thanks to Agriculture and Rural Development Office of the Dega Damot District as well as to the respective chairpersons for their assistance for field data collection.

Browse Subject Areas? Click through the PLOS taxonomy to find articles in your field. Abstract Plant community types are influenced by topographic factors, the physical and chemical properties of soil. Data Availability: All data are available with in the paper. Introduction The existence of plant communities is due to the interaction between plant species and their environment [ 1 ]. Materials and methods Description of the study area The study was carried out in a dry Afromontane forest landscape in Dega Damot district, Amhara Regional State, in the Northwestern part of Ethiopia.

Download: PPT. Fig 1. Location of forest patches in Dega Damot district, the star shows the small towns in the zone and in the district. Fig 2. Reconnaissance survey and sampling technique A reconnaissance survey was made in January across the forest patches to get an impression of the site conditions and identify the sampling sites in the study area. Table 2. Size, number of plots, transect and altitudinal range of forest patches.

Vegetation data collection In each plot, all individual trees and shrubs with a diameter at breast height DBH at 1. Environmental data collection Geographical data altitude, latitude, and longitude were recorded using GPS for each plot in the forest patches. Data analysis Plant community classification. Species diversity. Results Floristic composition A total of species, belonging to 80 families were recorded in the study area.

J Ecol 96 : — J Ecol 99 : — Funct Ecol 29 : — 9. Biometrics 60 : — 9. Ecology 90 : — Oxford : Blackwell Publishing. Ecol Indic 32 : 9 — Nord J Bot 31 : — J Ecol 93 : — J Ecol : — Ecology 95 : — J Math Model Algorithms 5 : — J Ecol : 93 — Ecography 35 : — Svenning JC On the role of microenvironmental heterogeneity in the ecology and diversification of neotropical rain-forest palms Arecaceae. Tarboton DG A new method for determination of flow directions and upslope areas in grid digital elevation models.

Water Resour Res 33 : — J Ecol 92 : — Species associations in a species-rich subtropical forest were not well-explained by stochastic geometry of biodiversity. Disentangling the effects of topography and space on distributions of dominant species in a subtropical forest. Chin Sci Bull 59 : — J Ecol 88 : — Oxford University Press is a department of the University of Oxford. It furthers the University's objective of excellence in research, scholarship, and education by publishing worldwide.

Sign In or Create an Account. Sign In. Advanced Search. Search Menu. Article Navigation. Close mobile search navigation Article Navigation. Volume Article Contents Abstract. Editor's Choice. Effects of topography on structuring species assemblages in a subtropical forest. Qinggang Wang , Qinggang Wang.

Oxford Academic. Ruwan Punchi-Manage. Zhijun Lu. Scott B. Zhiheng Wang. Yaoqi Li. Xiulian Chi. Dachuan Bao. Yili Guo. Junmeng Lu. Yaozhan Xu , Yaozhan Xu. Xiujuan Qiao.

Mingxi Jiang. Revision received:. Select Format Select format. Permissions Icon Permissions. Abstract Aims. Open in new tab Download slide. Table 1: results of MRT analyses and indicative species for all trees, three life stages sapling, juvenile and adult and two abundance levels common and rare in the ha Badagongshan Forest Dynamic Plot, Central China.

Total no. Variance Explained. Total species. Total stems. Habitat type. All species 0. Open in new tab. Table 2: the differences in variance explained by topographical habitats and the differences in Cross Validate Relative Error CVRE for MRT analyses between rare and abundant species; saplings and juveniles; and juveniles and adults. Soil resources and topography shape local tree community structure in tropical forests.

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R Development Core Team. Clustering rules: a comparison of partitioning and hierarchical clustering algorithms. Dispersal limitations, rather than bottlenecks or habitat specificity, can restrict the distribution of rare and endemic rainforest trees. Common and rare species respond similar niche processes in macroinvertebrate metacommunities. On the role of microenvironmental heterogeneity in the ecology and diversification of neotropical rain-forest palms Arecaceae.

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These differences in temperature, moisture, and exposure to wind and sun are called microclimates, and they are important predictors as to where various natural communities can be found.

For example, a windy hilltop with high evaporation and transpiration will tend to have a drier microclimate than a nearby sheltered ravine.

South-facing slopes will tend to be sunnier and drier than nearby north-facing slopes. This explains why snow melts away faster on south-facing slopes than on north-facing ones. A concave slope is like a bowl: it accumulates soil and moisture. A convex slope is the opposite.