Decomposition signals of warming in Arctic soils identified by FTICR and NMR

Abstract:

Northern latitudes contain large stocks of soil carbon vulnerable to decomposition with rapid warming in the Arctic. Within the Arctic, winter months are becoming more important because they are warming even faster than summer months, increasing overwinter rates of processes such as soil respiration. However, recent evidence indicates that overwinter soil respiration can become carbon limited. Hence a predictive understanding of soil respiration requires knowledge of temperature interactions with soil carbon availability at low temperatures. To do this we used FTICR and NMR to determine changes in tundra soil organic horizon extractable C chemistry in soils incubated from -4 to 20 deg. C. All soil subsamples were incubated at temperatures: below freezing (-4 deg. C) where microbial processes are known to be limited by low temperatures and ice but still active; just above freezing (4 deg.C) where some microbial reactions, such as macromolecule depolymerization, can be temperature limited, and a warm soil (20 deg. C) where the goal was to alleviate all temperature limitations to soil microbes. FTICR and NMR are being coupled to identify and quantify key reaction products from macromolecular decomposition. This will identify key molecular signals associated with decomposition and microbial activity that can be used to evaluate carbon availability to decomposers at low temperatures and guide future analyses.