Carbon and Nitrogen Isotopic Measurements from Southern Appalachian Soils: Assessing Soil Carbon Sequestration under Climate and Land-Use Variation

Abstract

Measurements of the distribution of carbon and nitrogen isotopes in soils are needed due to their potential to improve our understanding of soil CO 2 emissions and sequestration under varying climatic conditions and land management technologies. Organic carbon and nitrogen isotopic and elemental composition was measured in baseline forest soils as well as in anthropogenically and intermittently flooded soils in the southern Appalachian Mountains. For the undisturbed forest soils, the consistent relationship between elemental and isotopic composition in the soil column, across soil organic matter pools, was supportive of the hypothesis that isotopic signature is reflective of microbial induced carbon turnover and nitrogen decomposition. A climatologic analysis suggested that isotopic indicators of soil organic matter turnover were influenced by mean annual temperature at our study sites, as well as in 10 other regional and global soil carbon and nitrogen isotopic studies. Intermittently flooded soils showed carbon and nitrogen distributions that reflected successive high magnitude events where sediments were deposited upon a developing forest floor. Measurements from soils disturbed by mining, agriculture, and recreation suggest the potential for using carbon and nitrogen isotopes to indicate the degree of soil organic matter turnover induced by different land management scenarios.