Areas of residential development in the southern Appalachian Mountains are characterized by low riparian zone nitrogen cycling and no increase in soil greenhouse gas emissions

Abstract

The critical role streamside riparian zones play in mitigating the movement of nitrogen (N) and other elements from terrestrial to aquatic ecosystems could be threatened by residential development in the southern Appalachian Mountains. Many studies have investigated the influence of agriculture on N loading to streams but less is known about the impacts of residential development. Here we consider the dynamics of changing riparian land use in the southern Appalachians that includes increased residential development at the expense of both forests and agriculture. We hypothesized that increased inputs of inorganic N from residential development will increase nitrogen cycling rates relative to forests, thereby preventing terrestrial N retention and increasing soil nitrate losses through leaching. In addition, we hypothesized that such development will increase emissions of N2O, CO2, and CH4, all potent greenhouse gases. We found riparian soil potential N cycling rates as well as N2O and CO2 efflux to be much greater with agricultural land use compared to either forested or residential land use. Our data suggest that residential development of forested riparian ecosystems does not increase N cycling or removal and, thus, might allow for greater potential N leaching into streams. Both agricultural and residential land use exhibited CH4 efflux while forested ecosystems were responsible for CH4 uptake. Overall, regional greenhouse gas emissions are projected to decline as high N2O and CO2 emitting agricultural land is converted to residential use.