Soil Biogeochemistry: We are investigating the distribution of total soil carbon, soil CO2 concentrations, dissolved organic carbon (DOC), and soil microorganisms along hillslopes and with soil depth at the Shale Hills Critical Zone Observatory. These measurements will help us predict how soil microorganisms contribute to the weathering engine, and how soil development affects soil carbon storage and transport in this watershed. Jason Kaye (Department of Crop and Soil Sciences) and Susan Brantley (Geosciences) are interested in soil respiration rates at the Shale Hills Critical Zone Observatory. Soil respiration is the release of CO2 from plant roots and soil heterotrophic organisms to the atmosphere. Kaye’s group is working to quantify how water movement, water storage, and soil texture affect soil-atmosphere exchange rates of CO2. The flux of CO2 from soil is a critical component of the global carbon cycle, yet factors affecting this flux remain unclear.

Work by Danielle Andrews (advised by Henry Lin of Crop and Soil Sciences) examines how soil and landscape characteristics affect the movement of dissolved organic carbon (DOC) within the Shale Hills watershed. These studies indicate that DOC concentrations are correlated with topographic position. For instance, soil pore fluids in swale sites have elevated DOC relative to planar hillslope sites. Swales contain deeper soils than the planar hillslopes and are regions of convergent water flow that may facilitate organic matter collection and breakdown. Additionally, DOC concentrations were found to vary within the soil profile. For example, DOC increases above restrictive soil interfaces such as the clay-rich Bt horizon (Figure 1). Graduate student Tiffany Yesavage (advised by Susan Brantley of Geosciences) is investigating how variations in DOC and total carbon concentrations in turn may affect the distribution of different groups of microorganisms at different depths and topographic positions (Figure 2).

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The ultimate goal of this work is to understand how environmental parameters such as rates of regolith formation can be used to explain the distribution of CO2 and DOC in soils throughout the catchment. By creating this interdisciplinary team consisting of members from Crop and Soil Sciences and Geosciences, we hope to provide a theoretical basis for predicting soil carbon dynamics in shale-derived watersheds around the world.

 

Contacts: Jason Kaye (PI) and Susan Brantley (PI)