Presentation Title

Understanding the Biogeochemical Drivers of Dissolved Organic Carbon Dynamics: A Multiscalar Approach

Abstract

Variability in DOC export from forested headwater catchments has been attributed to an array of different hydrologic, biotic and geochemical drivers. A major challenge in understanding DOC dynamics has been relating long-term regional trends and patterns to specific processes at the catchment scale. We address this challenge by integrating methodologies that analyze trends and processes across different spatial scales. On the regional scale, we evaluate long-term monotonic trends in flow-adjusted DOC concentrations of headwater streams from the eastern United States. The direction of the trends is compared with catchment attributes compiled in a comprehensive and publicly available dataset, “Catchment Attributes and Meteorology for Large-Sample Studies” (CAMELS). At the catchment scale, we tested specific process-based hypotheses on the role of changes in rain composition (ionic strength and pH variations) on aggregate stability in riparian vs hillslope derived soils. This is accomplished through leaching experiments performed on top-soil cores from two forested headwater catchments (the Susquehanna Shale Hills Critical Zone Observatory in Pennsylvania and the Sleepers River Research Watershed in Vermont).

The results of the trend analysis display that there is clear regional heterogeneity in the dynamics of DOC in headwater catchments. However, while there was no clear evidence of geographic continuity, there is evidence of continuity in catchment attributes. Our results suggest that long-term increased DOC mobilization is in part a product of catchments with low landscape connectivity becoming more frequently connected as a function of increasing frequency in high precipitation storm events. Results of the leaching experiments indicate that DOC mobilization and aggregate stability as a function of rain composition are spatially specific on both the catchment and regional scale. Soils from the Sleepers River Watershed in Vermont consistently leached more DOC with aggregates destabilizing under lower ionic strength treatments. In the Susquehanna Shale Hills Critical Zone Observatory, DOC mobility and aggregate stability did not appear to respond the differently to the treatments, but did show variability based on catchment position.

Primary Faculty Mentor Name

Julia Perdrial

Status

Graduate

Student College

College of Arts and Sciences

Program/Major

Geology

Primary Research Category

Engineering & Physical Sciences

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Understanding the Biogeochemical Drivers of Dissolved Organic Carbon Dynamics: A Multiscalar Approach

Variability in DOC export from forested headwater catchments has been attributed to an array of different hydrologic, biotic and geochemical drivers. A major challenge in understanding DOC dynamics has been relating long-term regional trends and patterns to specific processes at the catchment scale. We address this challenge by integrating methodologies that analyze trends and processes across different spatial scales. On the regional scale, we evaluate long-term monotonic trends in flow-adjusted DOC concentrations of headwater streams from the eastern United States. The direction of the trends is compared with catchment attributes compiled in a comprehensive and publicly available dataset, “Catchment Attributes and Meteorology for Large-Sample Studies” (CAMELS). At the catchment scale, we tested specific process-based hypotheses on the role of changes in rain composition (ionic strength and pH variations) on aggregate stability in riparian vs hillslope derived soils. This is accomplished through leaching experiments performed on top-soil cores from two forested headwater catchments (the Susquehanna Shale Hills Critical Zone Observatory in Pennsylvania and the Sleepers River Research Watershed in Vermont).

The results of the trend analysis display that there is clear regional heterogeneity in the dynamics of DOC in headwater catchments. However, while there was no clear evidence of geographic continuity, there is evidence of continuity in catchment attributes. Our results suggest that long-term increased DOC mobilization is in part a product of catchments with low landscape connectivity becoming more frequently connected as a function of increasing frequency in high precipitation storm events. Results of the leaching experiments indicate that DOC mobilization and aggregate stability as a function of rain composition are spatially specific on both the catchment and regional scale. Soils from the Sleepers River Watershed in Vermont consistently leached more DOC with aggregates destabilizing under lower ionic strength treatments. In the Susquehanna Shale Hills Critical Zone Observatory, DOC mobility and aggregate stability did not appear to respond the differently to the treatments, but did show variability based on catchment position.