A COMPARISON OF N-ALKANE AND N-ACID ISOTOPIC COMPOSITION IN PLANTS, SOILS, AND LAKE SEDIMENT FROM THE BIG HORN MOUNTAINS IN WYOMING
Environmental stressors and hydrologic setting can affect the deuterium and carbon isotope composition of alkanes and alkanoic acids within vegetation, litter, and sediment. However, the relationships between the source (plants), intermediary (litter), and sink (lake sediment) are not well characterized. In plants, metabolic processes determine 13C and 2H fractionation, which varies with needle age, canopy position, tree age, season, and year. Soil litter integrates the vegetation signal across time and space and, therefore, deuterium and carbon isotopic variation decreases compared to the variation within needle samples at each site. Finally, we compared the deuterium and carbon isotope values of the pine needles and soil litter to surface samples from the sediment cores. Although these ponds are small and their watersheds were well sampled, organic particles transported from adjacent regions or autochthonous aquatic vegetation contributions may mask the terrestrial signal. By sampling the terrestrial vegetation and soil litter, we link the sedimentary isotopic signals to the variability within the watershed and evaluate the representativeness of the sediment samples. This study demonstrates the resolution of biomarker isotope composition on local and regional scales in lake sediments.