Microbial Abundance and Community Composition with Depth At Different Positions within An Agricultural Landscape.

Subsurface soil layers contribute significantly to global soil organic carbon (SOC) stocks, however, the controlling mechanisms of subsurface SOC dynamics are not well understood. Recent developments have suggested that surface and subsurface soil layers may exhibit differences in terms of SOC stabilization/destabilization mechanisms; one hypothesis proposes differences in microbial community structure and abundance with depth as a contributing factor.

The objective of this study is to characterize soil microbial community structure and abundance with depth in three different topographic positions (2 erosional; 1 depositional) within an agricultural landscape, and to relate potential differences to associated physiochemical conditions and carbon content. In the fall of 2010, A horizon samples were collected at 5 cm increments, including one buried A horizon extending to a depth of 90cm. Microbial community structure and relative abundance will be analyzed using phospholipid fatty acid (PLFA) analysis. It is expected that abundance of functional groups and microbial biomass will decrease with depth within each profile, and will vary between landscape positions. Assessing microbial community structure and abundance in this landscape will provide the basis for further work that aims to link community structure with function in terms of SOC cycling.