Linking process to pattern in community assembly in dry evergreen Afromontane forest of Hararghe highland, Southeast Ethiopia




Limiting similarity, environmental filtering, functional traits, spatial scale, non-metric dimensional scaling




Many scholars have attempted to identify the role of deterministic and stochastic processes in community assembly, but there is no consensus on which processes dominate and at what spatial scales they occur. To shed light on this issue, we tested two non-exclusive processes, scale-dependent hypotheses: (i) that limiting similarity dominates on small spatial scales; and (ii) that environmental filtering does so on a large scale. To achieve this, we studied the functional patterns of dry evergreen Afromontane forest communities along elevation gradients in southeastern Ethiopia using floristic and functional trait data from fifty-four 0.04 ha plots. We found evidence of functional overdispersion on small spatial scales, and functional clustering on large spatial scales. The observed clustering pattern, consistent with an environmental filtering process, was most evident when environmental differences between a pair of plots were maximized. To strengthen the link between the observed community functioning pattern and the underlying process of environmental filtering, we demonstrated differences in the topographical factors of the most abundant species found at lower and higher elevations and examined whether their abundance varied over time or changed with time along the elevation. We found (i) that the largest functional differences in the community (observed between lower and upper dry evergreen Afromontane forest assemblages) were primarily the result of strong topographical influence; and (ii) that the abundance of such species varied along the elevation gradient. Variation in stand structure and tree species diversity within the DAF plots shows that topography is among the important drivers of local species distribution and hence the maintenance of tree diversity in dry Afromontane forest.

Our results support the conclusion that environmental filtering at large spatial scales is the primary mechanism for community merging, since functional grouping pattern was associated with species similarities in topographic variation, ultimately leading to changes in species abundances along the gradient. There was also evidence of competitive exclusion at more homogeneous and smaller spatial scales, where plant species compete effectively for resources.

Author Biographies

Teshome Wondimu, Hawassa University

Wondo Genet College of Forestry and Natural Resources, Hawassa University, 

P.O.Box 128


Muktar Mohammed , Oda Bultum University

Oda Bultum University
P.O.Box: 226, Chiro, Ethiopia
TEL: + 251 915743701 or +251930313005



Abiyot Berhanu, Zerihun Woldu & Sebsebe Demissew. 2016. Elevation patterns of woody taxa richness in the evergreen Afromontane vegetation of Ethiopia. Journal of Forestry Research 28: 787-793.

Ali, A., Lin, S.L., He, J.K., Kong, F.M., Yu, J.H. & Jiang, H.S. (2018) Climatic water availability is the main limiting factor of biotic attributes across large-scale elevational gradients in tropical forests. Sci Total Environ, 647, 1211–1221.

Ali, A., Lin, S.L., He, J.K., Kong, F.M., Yu, J.H. & Jiang, H.S. (2019) Elucidating space, climate, edaphic and biodiversity effects on aboveground biomass in tropical forests. Land Degradation and Development.

Andersen, K.M., Endara, M.J., Turner, B. L. & Dalling, J.W. (2012). Trait-based community assembly of understory palms along a soil nutrient gradient in a lower montane tropical forest. Oecologia, 168, 519–531.

Arellano G, Cala V, Fuentes A, Cayola L, Jørgensen PM & Macía MJ. (2016) A standard protocol for woody plant inventories and soil characterization using temporary 0.1-ha plots in tropical forests. Journal of Tropical Forest Science, 28(4), 508–516.

Baraloto, C. et al. (2012) Using functional traits and phylogenetic trees to examine the assembly of tropical tree communities. Journal of Ecology, 100, 690–701.

Cadotte, M.W. & Tucker, C.M. (2017) Should environmental filtering be abandoned? Trends in Ecology and Evolution, 32, 429–437.

Cavender-Bares, J., Ackerly, D.D., Baum, D.A. & Bazzaz, F.A (2004) Phylogenetic overdispersion in Floridian Oak communities. American Naturalist, 163, 823–843.

Cavender-Bares, J., Kozak, K.H., Fine, P.V.A. & Kembel, S.W. (2009) The merging of community ecology and phylogenetic biology. Ecology Letters, 12, 693–715.

Chalmandrier, L. et al. (2017) Spatial scale and intraspecific trait variability mediate assembly rules in alpine grasslands. Journal of Ecology, 105, 277–287.

Chase, J.M. (2014) Spatial scale resolves the niche versus neutral theory debate. Journal of Vegetation Science, 25, 319–322.

Chave, J., Coomes, D., Jansen, S., Lewis, S.L., Swenson, N.G. & Zanne, A.E. (2009) Towards a worldwide wood economics spectrum. Ecology Letters, 12(4), 351–366.

Chiarucci, A., Maccherini, S. & De Dominicis, V. (2001) Evaluation and monitoring of the flora in a nature reserve by estimation methods. Biological Conservation, 101, 305-314.

Colwell, R.K. & Winkler, D. (1984) A null model for null models in biogeography. Pages 344–359 in Strong, D.R., Simberloff, D., Abele, L.G., & Thistle, A.B., editors. Ecological communities: conceptual issues and the evidence. Princeton University Press, Princeton, New Jersey, USA.

Cornelissen, J. H. C. et al. (2003) A Handbook of protocols for standardised and easy measurement of plant functional traits worldwide. European Journal of Ecology, 51, 335–380.

Cornwell, W.K. & Ackerly, D.D. (2010) A link between plant traits and abundance: Evidence from coastal California woody plants. Journal of Ecology, 98(4), 814–821.

Cornwell, W.K. & Ackerly, D.D. (2009) Community assembly and shifts in the distribution of functional trait values across an environmental gradient in coastal California. Ecological Monographs, 79, 109–126.

Cornwell, W.K. & Ackerly, D.D. (2015). Community assembly and shifts in plant trait distributions across an environmental gradient in coastal California. Ecological Monographs, 79, 109–126.

Cornwell, W.K., Schwilk, D. & Ackerly, D.D. (2006) A trait based test for habitat filtering: convex hull volume. Ecology, 87, 1465–1471.

de Bello, F., Lavorel, S., Lavergne, S., Albert, C.H., Boulangeat, I., Mazel, F. & Thuiller, W. (2013a) Hierarchical effects of environmental filters on the functional structure of plant communities: a case study in the French Alps. Ecography, 36, 393–402.

de Bello, F., Vandewalle, M., Reitalu, T., Leps, J., Prentice, H.C., Lavorel, S. & Sykes, M.T. (2013b) Evidence for scale- and disturbance-dependent trait assembly patterns in dry seminatural grasslands. Journal of Ecology, 101, 1237–1244.

De Cáceres, M., Legendre, P. & Moretti, M. (2010) Improving indicator species analysis by combining groups of sites. Oikos, 119(10), 1674–1684.

Di´az, S. & Cabido, M. (2001) Vive la difference: plant functional diversity matters to ecosystem processes. Trends in Ecology and Evolution, 16, 646–655.

Diamond, J.M. (1975) Assembly of species communities. Pages 342–444 in Cody, L., and Diamond, J., editors. Ecology and evolution of communities. Harvard University Press, Cambridge, Massachusetts, USA.

Donovan, L.A., Maherali, H., Caruso, C.M., Huber, H. & Kroon, H.D. (2011) The evolution of the worldwide leaf economics spectrum. Trends in Ecology and Evolution, 26(2), 88–95.

Dyer, J.M. 2009. Assessing topographic patterns in moisture use and stress using a water balance approach. Landscape Ecology 24(3): 391-403.

Edwards, S., Tadesse, M., Demissew, S. & Hedberg, I. (2000) Flora of Ethiopia and Eritrea. In: Magnoliaceae to Flacourtiaceae. The National Herbarium, vol. 2. Addis Ababa University, Addis Ababa & Uppsala (1).

Elias, E. (2016) Soils of the Ethiopian Highlands: Geomormology and Properties.CASCAPE Project, ALTERA, Wageningen University and Research Centre (Wageningen UR). The Netherlands.

Ermias Aynekulu, Aerts, R., Moonen, P., Denich, M., Kindeya Gebrehiwot, Va˚gen, T-G,. Wolde Mekuria & Boehmer, H.J. (2012) Altitudinal variation and conservation priorities of vegetation along the Great Rift Valley escarpment, northern Ethiopia. Biodiversity and Conservation, 21, 2691–2707.

Falster, D.S. & Westoby, M. (2003) Plant height and evolutionary games. Trends in Ecology and Evolution, 18, 337–343.

FAO. (2005) New_LocClim: local climate estimator (version 1.10). Environment and natural resources, working paper number 20 (CD-ROM). FAO, Rome.

Friis, I., Demissew, S. & van Breugel, P. (2010) Atlas of the potential vegetation of Ethiopia, Biologiske Skrifter, vol 58. The Royal Danish Academy of Science and Letters, Copenhagen.

Fukami, T., Bezemer, T.M., Mortimer, S.R. & Putten, W.H.V.D. (2005) Species divergence and trait convergence in experimental plant community assembly. Ecology Letters, 8(12), 1283–1290.

Funk, J.L., Larson, J.E., Ames, G.M., Butterfield, B.J., Cavender-Bares, J., Firn, J., et al. (2017). Revisiting the Holy Grail: Using plant functional traits to understand ecological processes. Biological Reviews, 92, 1156–1173.

Gallien, L. (2017) Intransitive competition and its effects on community functional diversity. Oikos, 126, 615–623.

Garnier, E., Cortez, J., Billès, G., Navas, M-L., Roumet, C., Debussche, M., et al. (2004) Plant functional markers capture ecosystem properties during secondary succession. Ecology, 85, 2630–2637.

Gauch, H.G., Whittaker, R.H. & Singer, S.B. (1981) A Comparative Study of Nonmetric Ordinations. The Journal of Ecology, 69(1), 135.

Getaneh Gebyehu, Teshome Soromessa, Tesfaye Bekele & Demel Teketay. (2019) Plant diversity and communities along environmental, harvesting and grazing gradients in dry Afromontane forests of Awi Zone, northwestern Ethiopia. Taiwania, 64(3), 307-320.

Gotelli, N.J. & Colwell, R.K. (2001) Quantifying biodiversity: procedures and pitfalls in the measurement and comparison of species richness. Ecology Letter, 4, 379–91.

Gotzenberger, L. et al. (2012). Ecological assembly rules in plant communities—approaches, patterns and prospects. Biological Reviews, 87, 111–127.

Green, P.T., Harms, K.E. & Connell, J.H. (2014) Nonrandom, diversifying processes are disproportionately strong in the smallest size classes of a tropical forest. Proceedings of the National Academy of Sciences of the United States of America, 111, 18649–18654.

Grieser J., Gommes, R. & Bernardi, M. (2006) New LocClim-the local climate estimator of FAO. Geophysical Research Abstracts, 8:2.

Grime, J.P. (2006) Trait convergence and trait divergence in herbaceous plant communities: Mechanisms and consequences. Journal of Vegetation Science, 17, 255–260.

Guo, Y., Wang, B., Mallik, A.U., Huang, F., Xiang, W., Ding, T., et al. (2017) Topographic species-habitat associations of tree species in a heterogeneous tropical forest. Journal of Plant Ecology 57, 1–10

Hedberg, I., Hedberg, O., Edwards, S. & Sebsebe Demissie. (1997) Flora of Ethiopia and Eritrea. Vol. 6, Hydrocharitaceae to Arecaceae, National Herbarium, Addis Ababa University.

Heino, J. & Tolonen, K.T. (2017) Ecological drivers of multiple facets of beta diversity in a lentic macroinvertebrate metacommunity. Limnology and Oceanography, 62, 2431–2444.

Hettenbererova, E., Hajek, M., Zelený, D., Jirouskova, J. & Mikulaskova, E. (2013) Changes in species richness and species composition of vascular plants and bryophytes along a moisture gradient. Preslia, 85, 369–388.

HilleRisLambers, J., P.B. Adler, W.S. Harpole, J.M. Levine & M.M. Mayfield. 2012. Rethinking community assembly through the lens of coexistence theory. Annual Review of Ecology, Evolution, and Systematics 43:227–248.

Hulshof, C.M. & Swenson, N.G. (2010) Variation in leaf functional trait values within and across individuals and species: An example from a Costa Rican dry forest. Functional Ecology, 24(24), 217–223.

Hulshof, C.M., Violle, C., Spasojevic, M.J., Mcgill, B., Damschen, E., Harrison, S., et al. (2013) Intra-specific and inter-specific variation in specific leaf area reveal the importance of abiotic and biotic drivers of species diversity across elevation and latitude. Journal of Vegetation Science, 24(5), 921–931.

Jiang, Z., Ma, K., Liu, H. & Tang, Z. (2018) A trait-based approach reveals the importance of biotic filter for elevational herb richness pattern. Journal of Biogeography, 00:1–11.

Kassambara, A. (2017) Practical guide to principal component methods in R: PCA, M (CA), FAMD, MFA, HCPC, factoextra. Vol. 2. STHDA.

Keddy, P.A. (1992) Assembly and response rules: two goals for predictive community ecology. Journal of Vegetation Science, 3, 157–164.

Kohyama, T., Suzuki, E., Partomihardjo, T., Yamada, T. & Kubo, T. (2003) Tree species differentiation in growth, recruitment and allometry in relation to maximum height in a Bornean mixed dipterocarp forest. Journal of Ecology, 91, 797–806.

Kraft, N.J.B. & Ackerly, D.D. (2010) Functional trait and phylogenetic tests of community assembly across spatial scales in an Amazonian forest. Ecological Monographs, 80:401–422.

Kraft, N.J.B., Adler, P.B., Godoy, O., James, E.C., Fuller, S. & Levine, J.M. (2015) Community assembly, coexistence and the environmental filtering metaphor. Functional Ecology, 29, 592–599.

Kraft, N.J.B., Valencia, R. & Ackerly, D.D. (2008) Functional traits and niche-based tree community assembly in an Amazonian forest. Science, 322, 580–582.

Kraft, N.J. & Ackerly, D.D. (2010) Functional trait and phylogenetic tests of community assembly across spatial scales in an Amazonian forest. Ecological Monographs, 80(3), 401–422.

Kraft, N.J.B., Godoy, O., & Levine, J.M. (2015) Plant functional traits and the multidimensional nature of species coexistence. Proceedings of the National Academy of Sciences USA, 112, 797–802.

Laliberte, E. & Legendre, P. (2010) A distance-based framework for measuring functional diversity from multiple traits. Ecology, 91, 299–305.

Lavorel, S. & Garnier, E. (2002) Predicting changes in community composition and ecosystem functioning from plant traits: Revisiting the Holy Grail. Functional Ecology, 16, 545–556.

Le Bagousse-Pinguet, Y., Gross, N., Maestre, F.T., Maire, V., de Bello, F., Fonseca, C.R., Kattge, J., Valencia, E., Leps, J. & Liancourt, P. (2017) Testing the environmental filtering concept in global drylands. Journal of Ecology, 105, 1058–1069.

Lebrija-Trejos, E., Meave, J.A., Bongers, F. & Poorter, L. (2010) Functional traits and environmental filtering drive community assembly in a species-rich tropical system. Ecology, 91(2), 386–398.

Legendre, P. (2008). Studying beta diversity: Ecological variation partitioning by multiple regression and canonical analysis. Journal of Plant Ecology, 1(1), 3–8.

Legendre, P. & Gallagher, E.D. (2001) Ecologically meaningful transformations for ordination of species data. Oecologia, 129(2), 271–280.

Legendre, P., Borcard, D. & Peres-Neto, P.R. (2005) Analyzing beta diversity: Partitioning the spatial variation of community composition data. Ecological Monographs, 75(4), 435–450.

Levin, S.A. (1992) The problem of pattern and scale in ecology. Ecology, 73, 1943–1967.

Lopez-Angulo, J., N.G. McGill, B.J. (2010) Matters of scale. Science, 328, 575–576.

Liu, J., Yunhong, T. & Slik, J.W.F. (2014) Topography related habitat associations of tree species traits, composition and diversity in a Chinese tropical forest. Forest Ecology and Management, 330, 75–81.

Luo, Y.H., Liu, J., Tan, S.L., Cadotte, M.W., Wang, Y.H., & Xu, K. et al. (2016) Trait-based community assembly along an elevational gradient in subalpine forests: Quantifying the roles of environmental factors in inter-and intraspecific variability. PLoS ONE, 11(5).

Magurran, A.E. & McGill, B.J. (2011) Biological diversity: frontiers in measurement and assessment. New York, Oxford University Press.

Mason, N.W.H. & Wilson, J.B. (2006) Mechanisms of species coexistence in a lawn community: Mutual corroboration between two independent assembly rules. Community Ecology, 7, 109–116.

Mason, N.W.H., de Bello, F., Dolezal, J. & Leps, J. (2011) Niche overlap reveals the effects of competition, disturbance and contrasting assembly processes in experimental grassland communities. Journal of Ecology, 99, 788–796.

Mason, N.W.H., Richardson, S.J., Peltzer, D.A., de Bello, F., Wardle, D.A. & Allen, R.B. (2012). Changes in coexistence mechanisms along a long-term soil chronosequence revealed by functional trait diversity. Journal of Ecology, 100, 678–689.

Mason, N.W.H., Richardson, S.J., Peltzer, D.A., de Bello, F., Wardle, D.A. & Allen, R.B. (2012) Changes in coexistence mechanisms along a long-term soil chronosequence revealed by functional trait diversity. Journal of Ecology, 100, 678–689.

Mayfield, M.M. & Levine, J.M. (2010) Opposing effects of competitive exclusion on the phylogenetic structure of communities. Ecology Letters, 13, 1085–1093.

Mcgill, B.J., Enquist, B.J., Weiher, E. & Westoby, M. (2006) Rebuilding community ecology from functional traits. Trends in Ecology and Evolution, 21(4), 178–185.

Mengistu Teshome, Zebene Asfaw & Gemedo Dalle (2020). Effect of environmental gradients on diversity and plant community distribution in remnant dry Afromontane forest of Mount Duro, Nagelle Arsi, Ethiopia. Biodiv. Res. Conserv., 58, 21-31.

Moeslund, J.E., Arge, L., Bøcher, P.K., Dalgaard, T. & Svenning, J.C. (2013) Topography as a driver of local terrestrial vascular plant diversity patterns. Nordic Journal of Botany, 31, 129–144.

Moles, A.T., Warton, D.I., Warman, L., Swenson, N.G., Laffan, S.W., Zanne, A.E., et al. (2009) Global patterns in plant height. J. Ecol. 97, 923–932.

Munkemuller, T. et al. (2013). Scale decisions can reverse conclusions on community assembly processes. Global Ecology and Biogeography, 23, 620–632.

Oksanen, J., Guillaume Blanchet, F., Friendly, M., Kindt, R., Legendre, P., McGlinn, D., et al. (2020) vegan: Community Ecology Package. R package version 2.5-7.

Ordonez, J.C., van Bodegom, P.M., Witte, J-P.M., Wright, I.J., Reich, P.B. & Aerts, R. (2009). A global study of relationships between leaf traits, climate and soil measures of nutrient fertility. Global Ecology and Biogeography, 18, 137–149.

Peres-Neto, P.R., Legendre, P., Dray, S. & Borcard, D. (2006) Variation partitioning of species data matrices: Estimation and comparison of fractions. Ecology, 87(10), 2614–2625.

Pérez-Harguindeguy, N., Díaz, S., Garnier, E., Lavorel, S., Poorter, H., Jaureguiberry, P. et al. (2013) New handbook for standardised measurement of plant functional traits worldwide. Australian Journal of Botany, 61(3): 167–234.

Purschke, O., Schmid, B. C., Sykes, M. T., Poschlod, P., Michalski, S. G., Durka, W., et al. (2013) Contrasting changes in taxonomic, phylogenetic and functional diversity during a long-term succession: insights into assembly processes. Journal of Ecology, 101(4), 857–866.

R Core Team. (2018) R: A language and environment for statistical computing. In R Foundation for statistical computing. Vienna: Austria

Sargent, R.D. & Ackerly, D.D. (2008) Plant–pollinator interactions and the assembly of plant communities. Trends in Ecology and Evolution, 23, 123–130.

Schamp, B. S., Chau, J. & Aarssen, L.W. (2008) Dispersion of traits related to competitive ability in an old-field plant community. Journal of Ecology, 96, 204–212.

Silvertown, J. (2004) Plant coexistence and the niche. Trends in Ecology and Evolution, 19, 605–611.

Snyder, R.E. & Chesson, P. (2004) How the spatial scales of dispersal, competition, and environmental heterogeneity interact to affect coexistence. American Naturalist, 164, 633–650.

Stoll, P. & Weiner, J. (2000) A neighborhood view of interactions among individual plants. Pages 11–27 in Dieckmann, U., Law, R., & Metz, J., editors. The geometry of ecological interactions: simplifying spatial complexity. Cambridge University Press, Cambridge, UK.

Stubbs, W.J. & Wilson, J.B. (2004) Evidence for limiting similarity in a sand dune community. Journal of Ecology, 92, 557–567.

Swenson, N.G., Enquist, B.J., Thompson, J. & Zimmerman, J.K. (2007) The influence of spatial and size scale on phylogenetic relatedness in tropical forest communities. Ecology, 88, 1770–1780.

Tadesse Woldemariam Gole, T. Borsch, M. Denich & Demel Teketay. (2008). Floristic composition and environmental factors characterizing coffee forests in southwest Ethiopia. Forest Ecology and Management, 255(7), 2138–2150.

Thompson, K., Petchey, O.L., Askew, A.P., Dunnett, N.P., Beckerman, A.P. & Willis, A.J. (2010) Little evidence for limiting similarity in a long-term study of a roadside plant community. Journal of Ecology, 98, 480–487.

Valencia, R.,. Foster, R.B, Villa, G., Condit, R., Svenning, J-Ch., Hernández, C., et al. (2004) Tree species distributions and local habitat variation in the Amazon: large forest plot in eastern Ecuador. Journal of Tropical Ecology, 92(2), 214–229.

Warren, R.J. & Bradford, M.A. (2011) The shape of things to come: woodland herb niche contraction begins during recruitment in mesic forest microhabitat. Proceedings of the Royal Society of London B: Biological Sciences, 278, 1390–1398.

Watkins, A.J. & Wilson, J.B. (2003) Local texture convergence: A new approach to seeking assembly rules. Oikos, 102, 525–532.

Weiher, E. & Keddy, P.A. (1995) Assembly rules, null models and trait dispersion: new questions from old patterns. Oikos, 74, 159–164.

Westoby, M. (1998) A leaf-height-seed (LHS) plant ecology strategy scheme. Plant Soil, 199, 213–227.

Westoby, M., Falster, D.S., Moles, A.T., And, P.A. V. & Wright, I.J., 2002. Plant ecological strategies: Some leading dimensions of variation between species. Annual Review of Ecology and Systematics, 33(1), 125–159.

White, S., Bork, E. & Cahill, J. (2014). Direct and indirect drivers of plant diversity responses to climate and clipping across northern temperate grassland. Ecology, 95, 3093–3103.

White, S., Bork, E. & Cahill, J. (2014) Direct and indirect drivers of plant diversity responses to climate and clipping across northern temperate grassland. Ecology, 95, 3093–3103.

Wright, I.J. et al. 2(004) The worldwide leaf economics spectrum. Nature, 428, 821–827.

Wright, I.J., Reich, P.B. & Westoby, M. (2001) Strategy shifts in leaf physiology, structure and nutrient content between species of high-and low-rainfall and high-and low-nutrient habitats. Functional Ecology, 15(4), 423–434.

Yang, J., Zhang, G., Ci, X., Swenson, N. G., Cao, M. & Sha, L., et al. (2014). Functional and phylogenetic assembly in a Chinese tropical tree community across size classes, spatial scales and habitats. Functional Ecology, 28(2), 520–529.




How to Cite

Asfaw, Z., Teshome Wondimu, M. ., & Mohammed Yusuf, M. . (2023). Linking process to pattern in community assembly in dry evergreen Afromontane forest of Hararghe highland, Southeast Ethiopia. European Journal of Ecology, 9(1).