Nutrient availability and late-stage decomposition

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Having measured litter decomposition rates in dozens of experiments over the last 20 years, I have concluded 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 use stable isotope analysis to determine the fate of litter carbon as it moves through the soil food web, and 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. I will also investigate the movement of N and characterize the nitrifying organisms in forest floors of different tree species with known differences in nitrate production and availability to improve our understanding of nitrogen cycling in forest soils and the factors that influence it. My findings will be communicated to modelers to assist to improving the reliability of ecosystem and carbon budget models used to inform decisions and policies related to forest management and carbon accounting.