Nutrient availability and late-stage decomposition

在过去20年里，我在数十次实验中测量了凋落物的分解速度，我得出的结论是，在我们更好地理解分解过程本身，特别是分解的后期阶段之前，我们不会在测量、建模或理解分解速度方面取得进一步的进展。我们对凋落物分解速率的大部分估计都是从排除了大型土壤动物的研究中得出的，因此可能严重曲解了长期的腐烂速率。土壤动物消耗的大部分凋落物通过肠道，而不是完全分解；因此，在我们能够准确预测和模拟凋落物分解之前，了解土壤动物粪便物质的命运是必要的。稳定同位素分析技术的最新发展使我们能够解决这个以前难以解决的问题。在拟议的研究中，我将使用稳定同位素分析来确定凋落物碳在土壤食物网中移动时的去向，并将蚂蚁巢中的C、N和P矿化速率与周围森林地面进行比较，以更好地反映不列颠哥伦比亚省干燥森林生态系统中的养分循环。我还将调查N的移动并描述不同树种森林地面中硝化细菌的特征，这些树种在硝酸盐产生和有效性方面存在已知差异，以加深我们对森林土壤中氮素循环及其影响因素的理解。我的发现将被传达给建模人员，以帮助提高生态系统和碳预算模型的可靠性，这些模型用于为与森林管理和碳核算有关的决策和政策提供信息。

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.