Molecular-Scale Organic Matter Composition of a Sub-Arctic Soil Profile: a C and N K-Edge XANES Study.

It is well known that organic plant detritus decomposes slowly at polar latitudes, resulting in accumulations of large quantities of C in the landscape. Global warming scenarios predict a positive feedback in these regions, where increased atmospheric temperatures can result in enhanced respiration in these biomes, resulting in accelerated CO₂ production. Polar soils also are subjected to cryoturbation, where organic surface material is entrained deep in the soil profile. Initial decomposition studies revealed that subsoil organic horizons were not respiring at the same rate as surface horizons, despite similar C contents. The purpose of this project is to elucidate the chemical structures of C and N in the organic and mineral soils throughout the profile of a subarctic soil, and to relate the organic chemistry to descriptors of microbial community dynamics.