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

土壤团聚过程是草地和森林生态系统的一个重要过程。虽然通常被评价为静态现象，但土壤团聚体是不断形成和退化的。吸收大量碳的土壤表现出团聚体的定期更替，但我们发现一些常见的草原土地利用导致土壤非常稳定。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。森林土壤结构的研究较少，受AMF影响的可能性较小，AMF在森林中的发生水平低于草原。因此，预计外生菌根真菌和腐生真菌对森林土壤的土壤聚集作用更为重要。我们的总体假设是，随着土地利用强度的增加，总聚集体将减少，同时大团聚体的周转增加，微团聚体的形成减少。我们将在田间（草地和森林）使用菌丝生长核心来分离真菌对聚集动力学的影响，并在温室中分离AMF，非AMF和细菌的影响。该项目侧重于研究土壤真菌的功能多样性（这里定义为聚集土壤的能力）如何受到土地利用的影响。我们期望这个项目的结果能够提供关于土地利用强度如何影响土壤聚集动力学的新信息，以及这些动力学如何受到土壤微生物之间相互作用的影响。

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.