COMPOSITIONAL GRADIENTS OF PLANT COMMUNITIES IN SUBMONTANE RAINFORESTS OF EASTERN TANZANIA

Abstract

MUNISHI, P. K. T., SHEAR, T. H., WENTWORTH, T. & TEMU, R. A. P. C. 2007. Compositional gradients
of plant communities in submontane rainforests of eastern Tanzania. This study classified plant communities
and examined the environmental correlates of community compositions in two submontane rainforests
on the ranges of Eastern Arc Mountains, Tanzania. Using agglomerative cluster analysis, indicator species
analysis and non-metric multidimensional scaling (NMS) ordination, based on importance value of tree
species, five distinct plant communities were identified in the Usambara and six in the Uluguru mountains.
The communities corresponded closely to variations in topography and soil physical and chemical properties.
The different communities occurred on clay soils in lower elevations and on sandy-clay to sandy-clay-loam
soils in higher elevations. Two topographic and 14 edaphic factors were significant correlates of plant
community composition. Elevation was the strongest correlate of community composition on individual
mountain range followed by percent clay and soil pH. Landform index and soil Na concentration were
the major factors in separating plant communities on the west Usambara and Uluguru Mountains. There
were appreciable variations in plant community compositions and patterns on the two mountain ranges.
The results suggest that plant community patterns in the Eastern Arc Mountains vary from one range
to another and are influenced by a complex of local heterogeneity in topographic and edaphic factors.
The complex of factors influencing plant distribution can have a big bearing in species restoration and
biodiversity conservation in the Eastern Arc Mountains.