DEVELOPMENT OF AN INDEX FOR ORGANIC MATTER QUALITY IN PEATLANDS SOILS

The vulnerability of peatland carbon reservoirs to decomposition in a warming climate remains a key uncertainty in Earth System Models. This will be determined in part by the “quality” of the peatland organic matter, i.e. the ease by which it is decomposed by the microbial community. We developed an index of organic matter quality based on the biochemical composition of the peat. The index uses a principal components analysis of proxies based on the carbohydrate composition, hydrolysable amino acids, C:N, pH, and nutrient availability in the peat porewater. The index was compared with measurements of aerobic and anaerobic respiration rates from microcosm incubations of peat from several depth intervals in cores collected from four areas of Miner Lake Bog (Fennville, MI). We found that both the index and respiration rates declined with depth in the cores. In general, the correlation between organic matter quality and respiration was strongest for aerobic CO2 production, intermediate for anaerobic CO2, and weakest for CH4. This indicates that organic matter quality is an important predictor of the vulnerability of peat to decomposition. However, other factors may be more important in determining CH4 production. With further development, the index can be employed in other peatlands to interpret the organic matter quality and predict future greenhouse gas emissions.