Litter decomposition and nitrogen cycling in forest soils: influences of tree species and site factors

在拟议中的研究中，我将测量几个常见的树种在常见的花园实验，以建立不同的N循环是树种之间的森林地面的N循环过程的毛利率和净利率，以及最有影响力的凋落物或森林地面的特性，在确定不同树种下的森林地面的优势N的形式和N通量。 这将告诉我们，为了林业、填海或应对气候变化的协助迁移而引入新树种将如何改变场地，特别是氮循环和可用性。我还将比较不同的气候，植被和土壤，这将提供新的见解土壤氮循环在天然林和影响这些周期的性质的因素，天然林中的N循环。 准确的分解预测和建模对于可靠地预测全球变化下生态系统中碳通量和平衡的变化至关重要。 我将测试两个建议的手段，以提高我们的能力，预测凋落物分解率-通过识别阈值，其中一个因素发挥压倒性的影响，和植物功能性状，准确地预测凋落物分解率。为此，我将使用长期实地实验的数据和样本，测量包括粗木质残体在内的凋落物的腐烂率。最后，我将测试新的假设，已经改变了我们对分解的思考-真正的木质素的分解开始早，是最活跃的早期分解，并在早期分解过程中的“木质素”的明显积累是由于新化合物的积累，而不是持久性的柠檬酸植物材料。我将测试这一点，通过测量浓度的变化Klason“木质素”和真正的木质素在凋落物在不同阶段的腐烂，以确定这些假设是否适用于北方森林中发生的分解在表面有机层。 这些研究将测试新的概念，提高我们预测和模拟森林土壤碳通量的能力。

In the proposed research, I will measure gross and net rates of N cycling processes in forest floors under several common tree species in common garden experiments to establish how divergent N cycling is amongst tree species, and the characteristics of the litter or forest floors that are most influential in determining the dominant N forms and N fluxes in forest floors under different tree species. This will inform us as to how introducing a new tree species for purposes of forestry, reclamation or assisted migration in response to climate change will alter the site, particularly nitrogen cycling and availability. I will also compare N cycling in natural forests that differ in climate, vegetation and soil, which will provide new insights into soil N cycling in natural forests and the factors that influence the nature of these cycles. Accurate prediction and modeling of decomposition is essential to reliably predicting changes in carbon fluxes and balances in ecosystems under global change. I will test two proposed means to improve our ability to predict rates of litter decomposition - through identification of thresholds at which one factor exerts overwhelming influence, and of plant functional traits that accurately predict rates of litter decomposition. For this I will use data and samples from long-term field experiments measuring rates of decay of litter including coarse woody debris. Finally I will test new hypotheses that have transformed our thinking about decomposition - that decomposition of true lignin begins early and is most active early in decomposition, and that the apparent accumulation of "lignin" during early decomposition is due to the accumulation of new compounds rather than persistence of recalcitrant plant material. I will test this by measuring changes in concentrations of Klason "lignin" and true lignin in litter at various stages of decay, to determine if these hypotheses apply to northern forests in which decomposition occurs in surface organic layers. These studies will test new concepts and improve our ability to predict and model carbon fluxes from forest soils.