EAGER: MSB: Collaborative Research: Chemical and Microbial Mechanisms Linking Litter Quality and Decomposition Rate

对驱动分解的化学和微生物机制缺乏机械上的理解。枯枝落叶中木质素：氮或木质素：纤维素的比例通常与分解速率呈负相关，常被用来预测质量损失。此外，传统的经验模型通常将微生物活动的一般模式与环境变量联系起来。这两种预测方法都是相互关联的；都不是明确表示底物和微生物活动的动态相互作用，而微生物活动决定了分解的速度。最近，一种分解的理论模型(Guild-Based Decomacy Model，GDM)将凋落物化学变化与微生物群落组成和生化活动的变化结合在一起，但该模型尚未得到实验验证。这个项目将测试一组假设，这些假设解决了木质素、纤维素、氮(N)和微生物群落组成之间的相互作用对凋落物分解速度的影响。结果将用于改进和验证GDM，从而改进对全球变化下分解的预测。模式植物拟南芥的木质素和纤维素浓度不同的突变株将用于凋落物分解实验。在阿拉斯加北部生态系统的施氮肥和对照地块中，这些垃圾的化学和微生物成分将被跟踪分解。DNA的核苷酸类似标记将允许在环境中确定假定的木质素和纤维素降解菌的相对丰度。就将拟南芥凋落物与自然凋落物相关联而言，该项目是高风险的。它在提供对生态系统动力学的更好的机械性和预测性理解方面是高回报的。更广泛的影响包括一种重要的模式植物在分解研究中的新应用，对一名毕业生和一名本科生的培训，以及为当地高中生开发夏季“突变人夏令营”。

A mechanistic understanding of the chemical and microbial mechanisms that drive decomposition is lacking. Lignin:nitrogen or lignin:cellulose ratios of litter are frequently negatively correlated with decomposition rates and are often used to predict mass loss. In addition, traditional empirical models typically relate generic patterns of microbial activity to environmental variables. Both predictive approaches are correlative; neither explicitly represents the dynamic interaction of substrate and microbial activity that determines the rate of decomposition. Recently, a theoretical model of decomposition (Guild-based Decomposition Model, GDM) integrated the dynamics of changing litter chemistry with changing microbial community composition and biochemical activities, but this model has yet to be experimentally validated. This project will test a set of hypotheses that address interactions among lignin, cellulose, nitrogen (N), and microbial community composition on decomposition rates of litter. Results will be used to refine and validate GDM, thus improving predictions of decomposition under global change. Mutant lines of the model plant Arabidopsis thaliana that vary in lignin and cellulose concentrations will be used for litter decomposition experiments. The chemical and microbial composition of that litter will be tracked as it decomposes in N-fertilized and control plots in an Alaskan boreal ecosystem. Nucleotide analog labeling of DNA will permit the determination of the relative abundance of putative lignin- and cellulose-degrading microbes in situ.This project is high-risk in terms of relating Arabidopsis litter to natural litter. It is high-payoff in terms of supplying a better mechanistic and predictive understanding of ecosystem dynamics. Broader impacts include a novel application of an important model plant to decomposition studies, training for one graduate and one undergraduate student, and development of a summer "Mutant Camp" for local high school students.