Influence of soil fauna on litter decomposition

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Having measured litter decomposition rates in dozens of experiments over the last 20 years, I have concluded (FEM) that 1) our expectations that changes in rates of litter decomposition explain several phenomena such as rich sites getting richer, or higher N availability in clearcut or fertilized forests are incorrect, and that we will make no further progress in measuring, modeling or understanding decomposition rates until we better understand the process itself, in particular the later stages of decomposition.  Most of our estimates of litter decomposition rates have been derived from studies in which soil macrofauna have been excluded, and thus may seriously misrepresent long-term decay rates.  Most of the litter consumed by soil fauna is passed through the gut rather than completely decomposed; thus understanding of the fate of fecal material of soil fauna is necessary before we can accurately predict and model litter decomposition. Recent development of stable isotope analysis techniques allows us to address this previously intractable problem.   In the proposed research, I will 1) characterize soil faunal communities and nutrient availability in forests across a range of site conditions and under different tree species, 2) determine relationships between soil faunal and microbial communities and nutrient availability, 3 determine whether soil faunal and microbial communities are more closely correlated to broad factors such as regional climate, or to fundamental site factors such as soil texture, soil type, slope position, aspect, or to the nature of the trees and other vegetation on the site, 4) use stable isotope analysis to determine the fate of litter carbon as it moves through the soil food web, and 5) compare rates of C, N and P mineralization in ant nests compared with surrounding forest floor to better represent nutrient cycling in dry forest ecosystems in B.C.