NSFDEB-NERC: Mycorrhizal drivers of soil organic matter formation and decomposition

土地覆盖的变化，例如从草原到森林的转变，或者从森林到草原的转变，已经成为一种常见的现象。土壤微生物的变化，如与植物根结构相关的真菌，可能伴随着这些植被的变化。由于土壤有机质的形成和分解是由植物-微生物-土壤相互作用决定的，因此土地覆盖的变化可能会导致土壤有机质的积累、储存和物理保护的变化。这个美英合作项目，使用最先进的方法，将调查草原和森林如何利用它们不同类型的共生根部真菌，转化植物残渣输入和土壤有机质。实验将确定从草原到森林的过渡是增强还是退化土壤。此外，这项研究将创造新的计算工具来模拟土壤，以更好地预测土地覆盖变化后的碳和氮动态。这项研究将通过对未来陆地碳循环的更准确预测，帮助管理者确定可持续的土地管理决策。除了国际合作，该项目还将为博士后科学家和本科生提供指导。这项研究将(1)确定温带牧草和针叶树与其相关菌根相互作用影响土壤有机质形成和分解的机制；(2)将这一机制理解整合到一个新的基于过程的模型中；(3)利用现有的从草原到森林的土地利用变化的时间序列来独立验证生态系统C库长期变化的模型预测。该项目包括一套完整的温室、田间和模型研究，不同的组成部分在美国和英国进行。植物和菌根生物量的连续13C同位素标记将被用来准确追踪根分泌物和菌根产物形成颗粒或溶解有机物时的命运，然后通过物理封闭或矿物质结合来稳定。在野外，将确定不同的菌根类型对13C标记的草和树木残留物的分解、二氧化碳产生和土壤有机质形成的影响。贝叶斯推理将用于使用实验数据对新模型进行参数化，模型预测将使用从草原到森林过渡时间序列收集的碳储量变化数据进行评估。土壤有机质因物理遮挡或矿物组合而稳定的程度将被用来评估基于过程模型的结果，并说明新模型作为碳循环预测和生态系统管理的政策工具的可靠性。

Changes in land cover, such as the transition from grassland to forest, or vice-versa, have become a common occurrence. Changes in soil microorganisms, such as fungi associated with plant root structures, can accompany these vegetation changes. Because the formation and decomposition of soil organic matter is determined by plant-microbe-soil interactions, the land-cover change may result in a change in the accrual, storage and physical protection of soil organic matter. This US-UK collaborative project, using state-of-the-art methods, will investigate how grasslands and forests, with their different types of symbiotic root fungi, transform plant residue inputs and soil organic matter. Experiments will determine whether the transition from grassland to forests enhances or degrades soils. Additionally, the research will create new computational tools to model soils to better predict carbon and nitrogen dynamics after land cover change. This research will help managers identify sustainable land management decisions through more accurate forecasting of future terrestrial carbon cycling. In addition to international collaboration, this project will provide mentoring for post-doctoral scientists and undergraduate students. This research will (1) determine the mechanisms by which temperate grasses and coniferous trees in interaction with their associated mycorrhizae affect soil organic matter formation and decomposition; (2) integrate this mechanistic understanding in a new process based model; and (3) use existing chronosequences of land use change from grassland to forest to independently verify model projections of long-term changes in ecosystem C stores. The project consists in an integrated set of greenhouse, field and modelling studies, with different components carried out in the US and UK. Continuous 13C isotope-labeling of plant and mycorrhizal biomass will be used to accurately trace the fate of root exudates and mycorrhizal products as they form particulate or dissolved organic matter, and then stabilize via physical occlusion or mineral bonding. In the field, the effects of different mycorrhizal types on the decomposition of 13C-labeled grass and tree residues, CO2 production, and soil organic matter formation will be determined. Bayesian inference will be used to parameterize the new model using the experimental data, and model projections will be evaluated using data on carbon stock changes collected from a grassland-forest transition chronosequences. The degree of soil organic matter stabilization by physical occlusion or mineral-association will be used to evaluate the process-model based findings and inform on the reliability of the new model as a policy tool for C cycling projections and ecosystem management.