The influence of land cover on dissolved organic carbon in Marquette County, Michigan streams

Dissolved organic carbon (DOC) has a variety of important functions in streams, from providing a food source for microbes to binding nutrients and metals.  DOC concentrations have been shown to correlate with various watershed and land cover metrics such as watershed area and the percent of watershed that is wetlands.   Areas with deep groundwater flow often have low DOC concentrations due to adsorpsion of DOC in inorganic soils.  Flow in riparian areas is often shallow and in contact with more organic material, making shallow flow more representative of the land cover it drains.  We hypothesized that riparian area and land cover would be more strongly correlated with DOC concentrations than watershed area and land use.  DOC was quantified from 26 streams three times during the growing season of 2008 in Marquette County of Michigan’s Upper Peninsula.  Concentrations ranged from 1.9 to 48.1 mg C L^-1.  Land cover was determined using both the National Land Cover Dataset (NLCD) and the National Wetland Inventory (NWI).  There were no significant correlations between DOC concentration and watershed area or land cover for both the NLCD and the NWI.   Riparian area and land cover were more strongly correlated with DOC concentrations than their watershed-level counterparts.