Does the abundance of dominant trees affect diversity of a widespread tropical woodland ecosystem in Tanzania
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Date
2015-05-04
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Cambridge University Press
Abstract
Dominant woody species can determine the structure and composition of a plant community by affecting
environmental conditions experienced by other species. We explored how dominant tree species affect the tree species
richness, diversity, evenness and vertical structural heterogeneity of non-dominant species in wet and dry miombo
woodlands of Tanzania. We sampled 146 plots from eight districts with miombo woodlands, covering a wide range of
topographic and climatic conditions. We recorded 217 woody plant species belonging to 48 families and 122 genera.
Regression analysis showed significant negative linear associations between tree species richness, relative species
profile index of the non-dominant and the relative abundance of the dominant tree species (Brachystegia spiciformis
and Brachystegia microphylla in wet, and Brachystegia spiciformis and Julbernardia globiflora in dry miombo woodlands).
Shannon diversity and evenness had strong non-linear negative relationships with relative abundance of dominant
tree species. A large number of small individual stems from dominant and non-dominant tree species suggesting good
regeneration conditions, and intensive competition affecting survival. We suggest that dominant miombo tree species
are suppressing the non-dominant miombo tree species, especially in areas with high recruitments, perhaps because
of their important adaptive features (extensive root systems and ectomycorrhizal associations), which enhance their
ability to access limited nutrients.
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Keywords
Coexistence, Heterogeneity, Richness, Structure, Tree species