Terrestrial ecosystems may have significant feedbacks to global climate change, although the magnitude and direction of these feedbacks is largely unknown. Boreal wetlands are of particular importance due to their large extent, production of anaerobic "greenhouse" gases, globally significant stores of carbon in peat, and potential feedbacks with increased temperatures. We propose to manipulate water-table levels and soil temperatures in bog and fen mesocosms to determine the direct and indirect feedbacks between climate change and southern boreal peatlands. Intact blocks of peat, with the accompanying shrub, moss, and graminoid vegetation layers will be used. Also, the regional groundwater flow in natural fens will be simulated. A full array of community and ecosystem responses will be measured, including trace gas fluxes, nutrient mineralization and availability, net changes in carbon and nutrient pools, changes in soil substrate quality over time, pore water chemistry, plant community composition, plant nutrient uptake, plant and microbial biomass, and primary productivity. %%% Our central hypothesis is: Temperature and aeration status directly control the rates and partitioning of trace gas fluxes and soil nutrient availability in peatlands, but this climate - soil link is constrained by soil substrate quality. Soil nutrient availability in turn controls plant dynamics, which will feedback on soil substrate quality. The previous research of the investigators has shown that the three primary controlling variables (substrate quality, temperature, aeration status) interact in nonlinear, nonintuitive ways. Direct experimentation will unravel the hierarchy of controlling factors in boreal peatlands and allow us to make robust predictions of responses to future climate change.
