Compositional Controls on Carbon Storage in Peatlands

Peatlands cover a small percentage of the earth surface, but the exact mechanisms of how a third of the Earths global soil carbon is sequestered is not yet resolved. Therefore, this thesis aims to explore the relationship between the chemical composition of peat soils and organic matter and their response to various physical and environmental stimuli in three standalone projects, so that we may be able to better understand the fate of the carbon currently stored in peatland systems. (1) We analyzed peat samples from the Spruce and Peatland Responses Under Changing Environments (SPRUCE) project to explore ecosystem-scale warming effects on peatland carbon storage in vegetative organic matter using Fourier Transform Infrared spectroscopy (FTIR). We found that the depth of the sample had a larger effect than the amount of in situ heat the sample was exposed to. (2) Wooden blocks were positioned at pre-determined depths within the peat soil horizon in a bog in tropical Borneo and incrementally removed at different time points, with the last blocks being removed after eight years in situ. By taking dimensional data from the blocks, and using FTIR to observe any shift in chemical composition, we found that the blocks mechanically decayed before large trends in chemistry emerged. Depth of the blocks and exposure to aerobic conditions were important drivers in the rate of decay in this bog system. (3) To observe how carbohydrate content drives the rate of CO2, CH4 production in anoxic peatland systems, we created incubations from peat samples representing a range of latitudes and parent vegetation. We found that the carbohydrate content positively drove the rate of CO2, CH4 production; but this was only true for samples that were not from habitats that primarily consist of Sphagnum moss. Results from our projects suggest that the current store of carbon in peatlands are compositionally stable under stress from a changing climate, at least on the timescale of this experiment. Further work is needed to fully understand the processes that govern controls on carbon storage in peatland systems as our findings raise questions that the scope of our studies do not answer.