Abstract
We studied the influence of east and west aspects on floristic composition, diversity, structure and treeline of afromontane cloud forests at Rira in the Bale Mountains, southeast Ethiopia. In addition, we studied how aspect relates to and/or interacts with other topographic and edaphic factors in influencing vegetation diversity. Stratified systematic plot sampling was used to survey the floristic composition, diversity and structure of forests on east- and west-facing slopes. The sample plot size was 20 × 20 m and a total of 36 plots were inventoried. A total of 72 composite soil samples were collected and analysed. Woody species richness of the forest on the east-facing slope was 1.7 times higher than on the west-facing slope. Shannon, Simpson and Log-series alpha diversity indices and evenness of forests on the east-facing slope were significantly higher than on the west-facing slope. NMDS ordination indicated that the east- and west-facing slopes formed two clusters of species and aspect explained 55.2 % and 10.4 % of the variation in species richness and abundance, respectively. There was no significant difference between aspects in stand structure except in dominant height, which was higher on the east-facing slopes. There was significant interaction between aspect and elevation in influencing woody species diversity. The four plant community groups, which were identified using cluster and indicator species analysis were represented differently on the east and west aspects. The treeline on the east-facing slope (3352 m) was located about 110 m higher than on the west-facing slope (3240 m). Soil moisture deficiency was unlikely to be a limiting factor on either site. Near the equator, east–west aspect was shown to have considerable impact on floristic composition, diversity, structure, and treeline position of montane forests. Diurnal cloud movement patterns and its impact on microclimate of slope aspect should be taken into account in future studies of cloud forest diversity, structure, and treeline position.
Similar content being viewed by others
References
Amare T, Hergarten C, Hurni H, Wolfgramm B, Yitaferu B, Gebre Selassie Y (2013) Prediction of soil organic carbon for ethiopian highlands using soil spectroscopy. ISRN Soil Sci 2013:1–11. http://dx.doi.org/10.1155/2013/720589. http://www.hindawi.com/journals/isrn/2013/720589/ Accessed 14 Jan 2014
Badano EI, Cavieres LA, Molina-Montenegro MA, Quiroz CL (2005) Slope aspect influences plant association patterns in the Mediterranean matorral of central Chile. J Arid Environ 62:93–108
Bader MY, Ruijten JA (2008) A topography-based model of forest cover at the alpine tree line in the tropical Andes. J Biogeogr 35:711–723
Bale CL, Williams JB, Charley JL (1998) The impact of aspect on forest structure and floristics in some Eastern Australian sites. For Ecol Manag 110:363–377
Barnes BV, Zak DR, Denton SR, Spur SH (1998) Forest ecology, 4th edn. Wiley, New York, p 792
Bekele T (1994) Vegetation ecology of remnant Afromontane forests of the central plateau of Shewa, Ethiopia. Acta Phytogeogr Suec 79:1–59
Brunori A, Nair PKR, Rockwood DL (1995) Performance of two Eucalyptus species at different slope positions and aspects in a contour-ridge planting system in the Negev desert of Israel. For Ecol Manag 75:41–48
Bussmann R (1997) The forest vegetation of the Harenna escarpment (Bale province, Ethiopia)—syntaxonomy and phytogeographical affinities. Phytocoenologia 27(1):1–23
Dalen L, Hofgaard A (2005) Diffrentail regional tree dynamics in the Scandes mountains. Antarct Alp Res 37(3):284–296
Danby R (2003) A multiscale study of tree-line dynamics in southwestern yukon. Arctic 56(4):427–436
Edwards S, Demissew S, Hedberg I (1997) Flora of Ethiopia and Eritrea: Hydrocharitaceae to Arecaceae, vol 6. The National Herbarium, Addis Ababa University, Addis Ababa, p 586
FAO (2005) New_LocClim: local climate estimator (version 1.10). Environment and natural resources, working paper number 20 (CD-ROM). FAO, Rome
Fekedulegn D, Hicks RR, Colbert JJ (2003) Influence of topographic aspect, precipitation and drought on radial growth of four major tree species in an Appalachian watershed. For Ecol Manag 177:409–425
Fekedulegn D, Colbert JJ, Rentch JS, Gottschalk KW (2004) Aspect differences in vegetation, soil and microclimatic characteristics of an Appalachian watershed. Castanea 69(2):92–108
Foster P (2001) The potential negative impacts of global climate change on tropical montane cloud forests. Earth-Sci Rev 55:73–106
Frazer GW, Canham CD, Lertzman KP (1999) Gap light analyzer (GLA), version 2.0: imaging software to extract canopy structure and gap light transmission indices from true-colour fisheye photographs, users manual and program documentation. Millbrook, Simon Fraser University, Burnaby, British Columbia, and the Institute of Ecosystem Studies
Friis I, Demissew S, Breugel P (2010) Atlas of the potential vegetation of Ethiopia. Det Kongelige Danske Videnskabernes Selskab, Copenhagen, p 306
Gallardo-Cruz JA, Perez-Garcia EA, Meave JA (2009) β-diversity and vegetation structure as influenced by slope aspect and altitude in a seasonally dry tropical landscape. Landscape Ecol 24:473–482
Gaston KJ (1994) Rarity. Population and community biology series 13. Chapman and Hall, London, p 205
Grace J, Berninger F, Nagy L (2002) Impacts of climate change on tree line. Ann Bot 90:537–544
Grieser J, Gommes R, Bernardi M (2006) New LocClim—the local climate estimator of FAO. Geophys Res Abstr 8:2
Grubb PJ (1997) Control of forest growth and distribution on wet tropical mountains: with special reference to mineral nutrition. Annu Rev Ecol Syst 8:83–107
Hamilton LS (1995) Mountain cloud forest conservation and research: a synopsis. Mt Res Dev 15(3):259–266
Hedberg I, Edwards S (1989) Flora of Ethiopia, vol 3. Pittosporaceae to Araliaceae. The National Herbarium, Addis Ababa and Uppsala University, Uppsala, p 659
Hedberg I, Edwards S, Nemomissa S (2003) Flora of Ethiopia and Eritrea, vol 4(2). Part 1: Apiaceae to Dipsacaceae. The National Herbarium, Addis Ababa and Uppsala University, Uppsala
Hillman JC (1988) The Bale mountain national park area, southeast Ethiopia, and its management. Mt Res Dev 8(2/3):253–258
Hitimana J, Kiyiapi JL, Njunge JT (2004) Forest structure characteristics in disturbed and undisturbed sites of Mt. Elgon moist lower montane forest, western Kenya. For Ecol Manag 194:269–291
Holland PG, Steyn DG (1975) Vegetational responses to latitudinal variations in slope angle and aspect. J Biogeogr 2:179–183
Johansson MU, Fetene M, Malmer A, Granström A (2012) Tending for cattle: traditional fire managment in Ethiopian montane heathlands. Ecol Soc 17(3):19
Kebede M, Kanninen M, Yirdaw E, Lemenih M (2013) Vegetation structural characteristics and topographic factors in the remnant moist Afromontane forest of Wondo Genet, south central Ethiopia. J For Res 24(3):419–430
Kinjanjui JM, Karachi M, Ondimu KN (2013) Natural regeneration and ecological recovery in Mau forest complex. Kenya. Open J Ecol 3(6):417–422
Körner C (1998) A re-assessment of high elevation tree-line positions and their explanation. Oecologia 115:445–459
Lulekal E, Kelbessa E, Bekele T, Yineger H (2008) Plant species composition and structure of the Mana Angetu moist montane forest, south-eastern Ethiopia. J East Afr Nat Hist 97(2):165–185
McCune B, Dylan K (2002) Equations for potential annual direct incident radiation and heat load. J Veg Sci 13:603–606
McCune B, Grace BJ (2002) Analysis of ecological communities. MJM Softw Des, Oregon, p 300
McCune B, Mefford MJ (2011) PC-ORD. Multivariate analysis of ecological data, version 6. MjM Software, Gleneden Beach
Miehe G, Miehe S (1994) Zur oberen Waldgrenze in tropischen Gebirgen. Phytocoenologia 24:53–110
Moore PD (2008) Tropical forests. Facts on File Inc, New York, p 246
Negash M, Starr M (2013) Litterfall production and associated carbon and nitrogen fluxes of seven woody species grown in indigenous agroforestry systems in the south-eastern Rift Valley escarpment of Ethiopia. Nutr Cycl Agroecosyst 97:29–41
Nigatu L, Tadesse M (1989) An ecological study of the vegetation of the Harenna forest, Bale, Ethiopia. Sinet 12(1):63–93
Pallant J (2001) SPSS survival manual: a step by step guide to data analysis using SPSS for windows. Open University Press, Buckingham, p 334
R Core Team (2013) R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna. http://www.R-project.org
Rahbek C (1995) The elevational gradient of species richness: a uniform pattern? Ecography 18(2):200–205
Ritchie JT, Gerakis A, Suleiman A (1999) Simple model to estimate field-measured soil water limits. Trans ASAE 42(6):1609–1614
Sariyildiz T, Anderson JM, Kucuk M (2005) Effects of tree species and topography on soil chemistry, litter quality, and decomposition in Northeast Turkey. Soil Biol Biochem 37:1695–1706
Scatena FN, Bruijnzeel LA, Bubb P, Das S (2010) Setting the stage. In: Bruijnzeel LA, Scatena FN, Hamilton LS (eds) Tropical montane cloud forests: science for conservation and management. Cambridge University Press, Cambridge, pp 3–13
Schnitzer M (1982) Organic matter characterization. In: Page AL, Miller RHA, Keeney DR (eds) Methods of soil analysis. Part 2: Chemical and microbiological properties. American Society of Agronomy, Inc. and Soil Science Society of America, Inc., Madison, pp 581–594
Senbeta F, Denich M (2006) Effects of wild coffee management on species diversity in the Afromontane rainforests of Ethiopia. For Ecol Manag 232:68–74
Smith JMB (1977) Vegetation and microclimate of east and west-facing slopes in the grasslands of MT Wilhelm, Papua New Guinea. J Ecol 65(1):39–53
Tadesse M, Nigatu L (1996) An ecological and ethnobotanical study of wild or spontaneous coffee, Coffea arabica in Ethiopia. In: van der Maesen JG, van der Burgt XM, van Medenbach de Rooy JM (eds) The biodiversity of african plants. Kluwer, Dodrecht, pp 277–294
Tallents LA, Macdonald DW (2011) Mapping high-altitude vegetation in the bale mountains. Walia, Ethiopia, pp 97–117. doi:10.1111/j.1365-2656.2011.01911.x
Teketay D, Bekele T (1995) Floristic composition of Wof-Washa natural forest, Central Ethiopia: implications for the conservation of biodiversity. Feddes Repert 106:127–147
Tesfaye G, Teketay D, Fetene M (2002) Regeneration of fourteen tree species in Harenna forest, southeastern Ethiopia. Flora 197:461–474
Tesfaye G, Teketay D, Assefa Y, Fetene M (2004) The impact of fire on the soil seed bank and regeneration of Harenna forest, southeastern Ethiopia. Mt Res Dev 24(4):354–361
Teshome E, Randall D, Kinahan A (2011) The changing face of the Bale Mountains National Park over 32 years: a study of land cover change. Walia, Ethiopia, pp 118–130
Uhlig SK (1988) Mountain forests and the upper tree limit on the southeastern plateau of Ethiopia. Mt Res Dev 8(2/3):227–234
Uhlig SK, Uhlig K (1991) Studies on the altitudinal zonation of forests and alpine plants in the central Bale Mountains, Ethiopia. Mt Res Dev 11(2):153–156
Wesche K (2003) The importance of occasional droughts for afroalpine landscape ecology. J Trop Ecol 19:197–208
Wesche K, Miehe G, Kaeppeli M (2000) The significance of fire for afroalpine ericaceous vegetation. Mt Res Dev 20(4):340–347
Yadav AS, Gupta SK (2006) Effect of micro-environment and human disturbance on diversity of woody species in the Sariska tiger project in India. For Ecol Manag 225:178–189
Yimer F, Ledin S, Abdelkadir A (2006a) Soil property variations in relation to topographic aspect and vegetation community in the south-eastern highlands of Ethiopia. For Ecol Manag 232:90–99
Yimer Y, Ledin S, Abdelkadir A (2006b) Soil organic carbon and total nitrogen stocks as affected by topographic aspect and vegetation in the Bale Mountains, Ethiopia. Geoderm 135:335–344
Yimer Y, Ledin S, Abdelkadir A (2007) Change in soil organic carbon and total nitrogen content in three adjacent land use types in the Bale Mountains, south-eastern highlands of Ethiopia. For Ecol Manag 242:337–342
Zhang D, Hui D, Luo Y, Zhou G (2008) Rates of litter decomposition in terrestrial ecosystems: global patterns and controlling factors. J Plant Ecol 2:85–93
Acknowledgments
The authors are very grateful for the logistical support offered by the Wondo Genet College of Forestry and Natural Resources during the field work. The financial support of the Department of Forest Sciences, University of Helsinki is thankfully acknowledged.
Author information
Authors and Affiliations
Corresponding author
Additional information
Project funding: This study was financially supported by the Department of Forest Sciences, University of Helsinki.
The online version is available at http://www.springerlink.com
Corresponding editor: Zhu Hong
Rights and permissions
About this article
Cite this article
Yirdaw, E., Starr, M., Negash, M. et al. Influence of topographic aspect on floristic diversity, structure and treeline of afromontane cloud forests in the Bale Mountains, Ethiopia. J. For. Res. 26, 919–931 (2015). https://doi.org/10.1007/s11676-015-0155-4
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s11676-015-0155-4