The Alaska Peatland Experiment: two decades of hydrologic experiments show resilience in peatland CO2 respiration

Northern peatlands are experiencing some of the most rapid climate warming on the planet, which is compounded by increases in the extent and severity of climate-related disturbances such as drought, wildfire, and permafrost thaw.  Cumulatively these changes lead to both peatland wetting and drying at various scales. Since 2005, we have maintained large-scale flooding and drought experiments in an Alaskan rich fen. While peatland science is dominated by the paradigm that deep catotelm C is protected from mineralization by lack of O₂ supply, our results show remarkable resilience or lack of sensitivity of ecosystem respiration to fluctuations in water table position. This presentation will outline the rationale and support for three hypotheses we are testing to explain this trend: 1) changes in food web dynamics between detrital and algal channels promotes resilience in peatland autotrophic respiration; 2) changes in plant species composition in response to wetting or drying, such as increases in sedge abundance affects soil redox pool recharge and ultimately controls the ratio of CO₂ to methane production; and 3) humic substances contribute to the regeneration of electron acceptor pools via electron shuttling, leading to more sustained anaerobic respiration rates than previously described.  Support for these hypotheses are not mutually exclusive, and demonstrate that the influence of hydrologic changes on peatland carbon emissions will be mediated by complex vegetation and soil processes.