Document: GRE-3-52-55

The influence of edaphic factors and plant diversity on detritivore community composition: Termites and decomposition in semi-arid grasslands and woodlands of the Okavango Delta, Africa.

SCHUURMAN, G.W.*

University of Washington, Seattle, WA 98195, USA ¹

Abstract:
Understanding how communities contribute to biogeochemical processes is difficult because in most ecosystems much of mineralization, immobilization, and decomposition is mediated by complex mesofaunal and microbial communities. In semi-arid African savannas, however, decomposition is carried out primarily by the termite community, which is composed of readily identified and manipulated species. Study of this relatively simple decomposer community has revealed the importance of community composition in the ecosystem functioning of the decomposer subsystem. In particular, the presence of fungus-growing species of the sub-family Macrotermitinae, which vary in distribution and abundance, was associated with wood decomposition rates three times higher than in sites where they were absent. Following experimental determination of termite community composition, I used physical, chemical, and stable isotope analyses, to examine how edaphic factors and plant diversity influence termite diversity. Fungus comb stable carbon isotope ratios (ranging from -11.14 to -24.22 ⁰/ ₀₀ vs PDB) showed that the dominant, mound-building species, Macrotermes michaelseni, generally considered a grass specialist, consumes both grass (all C₄ in the study site) and wood litter and shows no clear preference. Results also showed that soil properties, particularly clay content, are important determinants of Macrotermitine distribution. Collectively, these findings suggest that edaphic factors have a major influence on termite distribution, while local plant diversity may have some influence on abundance but is a less important determinant of distribution.

Keywords: Decomposition, savanna, community ecology, stable isotopes, edaphic factors, termites, Macrotermitinae, Macrotermes

This abstract is being presented at: 3:15 PM in session:
Oral Session #67: Decomposition Processes.