HYDROLOGICAL IMPACTS ON WETLAND CARBON FLUX RESIDUALS

Wetland vegetation often takes in more atmospheric carbon dioxide (CO 2 ) during photosynthesis than it releases during respiration and decomposition. On the global scale, wetlands help moderate atmospheric CO 2 , the greatest contributor to anthropogenic climate warming. Carbon dioxide fluxes between the ecosystem and atmosphere measured at wetland sites help monitor the extent to which wetlands act as sinks, and sometimes sources, of atmospheric carbon and how their roles are changing over time. Precise model predictions of wetland carbon sequestration or expulsion are paramount to accurately diagnosing future concentrations of atmospheric carbon and the subsequent consequences to the climate system. However, significant model error exists in predicting these processes. Moreover, wet regions such as temperate wetlands are predicted to become wetter and warmer due to anthropogenic climate change. The ensuing impact on wetland hydrology and nutrient cycling will further complicate the prediction of CO 2 fluxes. To determine whether or not hydrology currently plays a prominent role in prediction error, the residuals between high-frequency multi-year carbon dioxide flux measurements from a Wisconsin and two Canadian wetland sites and the corresponding predictions from a suite of nearly one dozen independent ecosystem models are compared to observed water table measurements. A correlation between hydrology and model error would indicate how models could be improved to better predict the relationship between climate change and wetland carbon cycling.