The differences in diversity of ground-dwelling arthropod taxa under large and small trees

In the Kruger National Park, the factors that influence arthropod diversity and abundance are not well understood. However, arthropods are essential to the normal functioning of savanna ecosystems, and thus it is important to determine these factors. Because environmental factors associated with tree size may drive patterns of insect diversity and because park managers are actively investigating the impact of elephant damage on large tree populations, we aimed to assess the differences in arthropod communities beneath large and small trees with respect to several environmental characteristics including canopy cover, soil penetration, leaf litter mass, number of surrounding trees, and tree diameter, height, and canopy reach. Organisms were sampled using pitfall traps. We found that while arthropod species richness is not different between small and large trees, average arthropod abundance is greater beneath large trees. Specifically, we found that (1) diptera and coleoptera abundance is greater under large trees, (2) orthoptera abundance is greater under small trees, and (3) there is no difference in hymenoptera abundances. In a Spearman rank analysis, we found that though few correlations exist between insect abundances and the environmental factors measured, diptera abundance increases with tree diameter, height and canopy reach. The observed differences in arthropod abundance between small and large trees suggest that a mixture of trees of different sizes throughout these ecosystems contributes to heterogeneity of insect diversity in the landscape.