Density fractionation of soils from the Nevada Desert FACE Facility

These data are the result of a soil density fractionation experiment conducted on soils from the Nevada Desert FACE (Free Air Carbon Dioxide Enrichment) Facility located in Mars, NV. This study was a 10 year experiment where an undisturbed arid ecosystem was exposed to elevated atmospheric CO2 (550 ppm). The experiment had three control plots and three elevated CO2 plots. At the end of the experiment, soils were harvested from beneath five major vegetation cover types and unvegetated interspace. These species included A. dumosa, L. tridentata, L. Pallidum, L. Andersonii, and P. rigida. Bulk soils were collected in 20 cm increments from 0-100 cm. Bulk density was measured as kg soil per m2 in 20 cm increments from each plot in the experiment. The bulk density used for stock calculations here was an average of the values taken at each depth across all 6 plots. The density fractionation was conducted using sodium polytungstate at 1.85 g cm^-3. A separate set of soils from the top 0-20 cm of the soil profile were also isolated into a < 20 um fraction for analysis by pyrolysis GC/MS. Heavy and light fraction were treated with HCl fumigation to remove inorganic carbon prior to analysis for organic C and 13C and non acidified samples were analyzed for total N and 15N at the Cornell Stable Isotope Lab. Pyrolysis GC/MS samples were analyzed at Dr. Grandy's lab at UNH.