|Smith, Tomorra -|
|Kolka, Randall -|
|Zhou, Xiaobo -|
|Helmers, Matthew -|
|Cruse, Richard -|
Submitted to: Biogeochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 10, 2014
Publication Date: April 27, 2014
Citation: Smith, T.E., Kolka, R.K., Zhou, X., Helmers, M.J., Cruse, R.M., Tomer, M.D. 2014. Effects of native perennial vegetation buffer strips on dissolved organic carbon in surface runoff from an agricultural landscape. Biogeochemistry. 120:121-132. Interpretive Summary: Dissolved organic carbon constitutes a small yet important part of a watershed's carbon budget because it is the most mobile and biologically reactive form of carbon. Agricultural practices which promote carbon sequestration may also influence dissolved organic carbon concentrations and load in surface runoff, consequently impacting stream ecosystem processes. This study evaluated how the presence, extent, and hillslope position of strips of native prairie vegetation (NPV) affected the concentration and mass load of dissolved organic carbon during a three-year (2008-2010) study of small agricultural watersheds in Iowa. Dissolved organic carbon concentrations were greatest where prairie strip occupied 10% of the watershed and were placed at the footslope. However, the total mass of dissolved organic carbon export was greatest from 100% cropped watersheds because the prairie vegetation reduced runoff volumes. Data from two reference watersheds restored to 100% native prairie showed that conversion to prairie reduced concentrations and loads of dissolved organic carbon losses in runoff. The incorporation of prairie strips into Midwest croplands can benefit stream ecosystems and water quality by decreasing loads of dissolved carbon delivered from uplands in runoff. This study complements prior-published results from the same experiment that showed nutrient and sediment losses were also decreased by prairie strips. These specific results will be of greatest interest to members of the scientific community who conduct research on carbon budgets and aquatic ecosystems in Midwestern agricultural landscapes.
Technical Abstract: Dissolved organic carbon (DOC) constitutes a small yet important part of a watershed’s carbon budget because it is the most mobile and biologically reactive form of carbon. Agricultural practices which promote carbon sequestration may also influence DOC concentrations and load in surface runoff, consequently impacting stream ecosystem processes. In a long-term experiment at the Neal Smith National Wildlife Refuge in central Iowa, four treatments with strips of native perennial vegetation (NPV) varying in slope position and extent (proportion of area) were randomly assigned among twelve small agricultural watersheds in a balanced incomplete block design. Runoff samples from 2008-2010 were analyzed for DOC concentrations and correlated with flow data to determine flow weighted DOC concentrations and flux per watershed area. From analysis over the three-year study, flow weighted DOC concentrations were greater in the 10% NPV at the footslope than the 20% NPV in contours watersheds. Differences in concentration were not reflected in loads because the NPV treatments reduced runoff volumes significantly. The findings suggest that of the four treatments, the conversion of 10% of an agricultural watershed's area into NPV in the footslope position significantly increased DOC concentrations but decreased export when compared to 100% agricultural watersheds. Results indicate that the incorporation of NPV as buffer strips may benefit surface water quality by decreasing DOC loading to streams. We also compared two watersheds that were restored to 100% NPV and found significant decreases in DOC concentrations and loads indicating that conversion to prairie leads to less watershed DOC export.