Stream carbon dynamics in low-gradient headwaters of a forested watershedThis article is part of a larger document. View the larger document here.
Headwater streams drain more than 70 percent of the total watershed area in the United States. Understanding of carbon dynamics in the headwater systems is of particular relevance for developing best silvicultural practices to reduce carbon export. This study was conducted in a low-gradient, predominantly forested watershed located in the Gulf Coastal Plain region, to (1) investigate spatiotemporal dynamics of carbon concentrations in the headwaters, (2) assess the relationships among stream carbon and nutrient conditions, and (3) quantify carbon export from the entire watershed. Fifteen sites were selected along four first-to-third order streams. Monthly and storm event water samples were collected from December 2005 to September 2007. These samples were analyzed for total and dissolved organic and inorganic carbon, nitrate/nitrite nitrogen, and total and dissolved phosphorus. In addition, instream water quality parameters (dissolved oxygen, temperature, pH) were measured monthly at each site to gather information on stream environmental conditions. The study found a seasonal variation of stream carbon concentration ranging from 9.6 to 30.0 mg/L with the lowest concentrations in January and February. There was a clear increasing trend of dissolved inorganic carbon from the winter to summer months, indicating a critical metabolic role of carbon supply and transport. Over the entire 22 months, the watershed exported a total of 1054.35 t carbon, in a decreasing trend of fluxes from 5.2 to 1.3 kg/ha per month with the increasing drainage area. This information can be useful for designing silvicultural practices that will conserve and maintain ecosystem carbon.