INFLUENTIAL ENVIRONMENTAL PARAMETERS CONTRIBUTING ON TREE SPECIES DISTRIBUTION IN TWO FORESTS OF THE EASTERN AFROMONTANE HOTSPOT, TANZANIA

Abstract

Understanding the influence of environmental parameters in determining tree species distribution and how it might change over time is a vital issue for species distribution modeling (SDM), yet it is poorly addressed in most of tropical forests and has not been addressed in the Eastern Arc Mountains (EAMs). This study was conducted with the objective of identifying most influencial environmental parameters contributing on tree species distribution in East Usambara Forests (EUF) and Udzungwa Mountain Forests (UMF) of the EAMs, Tanzania. Novel modelling method called Maximum Entropy Distribution (Maxent, version 3.3.3k), was used to model the distribution of eight most dominant tree species based on the frequency of occurence and 11 uncorrelated environmental variables. The drivers of species distribution in EUF and UMF are mainly climatic and edaphic factors. Climate change effects were driven by all climatic variables followed by edaphic variables while topographic factors had no effect. Soil factors have shown stronger effects in the UMF than in the EUF while the effects of temperature and precipitation were strong in both sites. Further studies on physiological responses and range shifts of selected species to environmental change (e.g climate change) within the EAMs are recommended.

Keywords: Climate change - Eastern Arc Mountains - Maxent modeling - Tree species distribution.