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FLOW RECESSION AND STREAM FLOW INTERMITTENCY DOMINATE ORGANIC CARBON CHEMISTRY IN A HEADWATER MOUNTAIN STREAM

The objective of this research is to understand how flow recession and stream flow intermittency influence the transport and transformation of dissolved organic carbon (DOC). We hypothesized that as flow decreases and intermittency increases, the dominant scale controlling the quantity and quality of DOC in the stream will shift from catchment scale processes (i.e. hillslope/riparian connectivity, lateral inputs) to local valley-bottom, surface water-groundwater exchange processes. In the summer of 2016, we collected monthly samples every 10 meters along a 500-meter mountainous reach in Oregon. Stream surface flow transitioned from continuous to intermittent over the summer, with 18% of the study reach dry in August. Across the three sampling events, mean DOC concentration increased from 1.09 to 2.06 mg L-1, and coefficient of variance of DOC concentration also increased. The correlation between upslope accumulation area and DOC concentration (used to assess catchment controls) weakened as flow decreased and was weakest during intermittent conditions. This study suggests that stream intermittency significantly impacts the governing spatial scale controls of DOC processing, leading to a shift from catchment scale to local scale control over DOC.

Stephen Plont (POC,Primary Presenter), Department of Earth and Environmental Sciences, Michigan State University, USA, plontste@msu.edu;


Jay Zarnetske ( Co-Presenter/Co-Author), Department of Earth and Environmental Sciences, Michigan State University, USA, jpz@msu.edu;


Adam Ward ( Co-Presenter/Co-Author), Indiana University, adamward@indiana.edu;


Noah Schmadel ( Co-Presenter/Co-Author), Indiana University, noahschm@indiana.edu;