Nitrate Sorption As a Mechanism to Buffer N Export At the Coweeta Hydrologic Laboratory.

The retention of nitrate (NO3- ) within forested catchments has been a focus of study in recent years partially due to the recognition of the potential negative impacts of chronic N deposition on forest ecosystem productivity and function and a growing concern regarding the eutrophication of adjacent aquatic ecosystems. Understanding mechanisms of NO3- retention within forest ecosystems and how retention capacity affects export across spatial, temporal and depositional scales is crucial for identifying ecosystems sensitive to such issues. Few studies have determined possible abiotic NO3- retention mechanisms in forest soils and their potential in buffering N export. We propose that NO3- sorption varies predictably based on soil chemical properties (e.g. organic matter, mineralogy, pH) and that NO3- sorption capacity will explain changes in soil-solution NO3- flux through mineral soil horizons during the dormant season when uptake is expected to be minimal. These relationships suggest that NO3- sorption may be a relevant and predictable mechanism to buffer NO3- export from forest ecosystems. The selective dissolution techniques used in this study allows for the possible application of this research to spatially explicit databases (e.g. STATSGO2) created by the NRCS State Soil Geographic database.