Dynamics of soil aggregation as affected by land use in grasslands and forests

草地和森林生态系统的一个重要过程是土壤聚集的动态过程。虽然通常被评估为静态现象，但土壤团聚体是不断形成和降解的。固持大量碳的土壤表现出规律性的团聚体周转，但我们发现，一些常见的草原土地利用导致了土壤的显著稳定。这种稳定性似乎至少部分归因于丛枝菌根真菌(AMF)的菌丝网络。森林中的土壤结构研究较少，也不太可能受到AMF的影响，AMF发生在森林中的水平低于草原。因此，外生菌根真菌和腐生真菌对森林土壤中的土壤团聚性具有更重要的作用。我们的总体假设是，随着土地利用强度的增加，总团聚体将减少，同时大团聚体的周转增加，微团聚体的形成减少。我们将在野外(草原和森林)使用菌丝生长核心来分离真菌对聚集动态的影响，并在温室中分离AMF、非AMF和细菌的影响。该项目的重点是土壤真菌的功能多样性，在这里定义为土壤聚集能力，如何受土地利用影响。我们期望该项目的结果能够为土地利用强度如何影响土壤团聚体的动态，以及土壤微生物之间的相互作用如何影响这些动态提供新的信息。

An important ecosystem process in grasslands and forests is the dynamic process of soil aggregation. Though often assessed as a static phenomenon, soil aggregates are constantly formed and degraded. Soils sequestering large amounts of C demonstrate regular turnover of aggregates, but we have found that some common grassland land uses lead to remarkably stable soils. This stability appears to be due, at least in part, to hyphal networks of arbuscular mycorrhizal fungi (AMF). Soil structure in forests is less well studied, and is less likely to be affected by AMF, which occur at lower levels in forests than in grasslands. Thus, ectomycorrhizal and saprophytic fungi are expected to be more important for soil aggregation in forest soils. Our overall hypothesis is that as land use intensity increases total aggregation will decrease, along with increased turnover of macroaggregates and decreased formation of microaggregates. We will use hyphal in-growth cores in the field (grassland and forest) to isolate fungal effects on aggregation dynamics, and in the greenhouse to separate effects of AMF, non-AMF, and bacteria. The project focuses on how functional diversity of soil fungi, defined here as ability to aggregate soils, is affected by land use. We expect the outcome of this project to provide novel information on how land-use intensity affects dynamics of soil aggregation, and on how those dynamics are influenced by interactions between soil microbes.