Multi-decadal Changes in Water Table Levels Alter Peatland Carbon Cycling

Globally, peatlands store a large quantity of soil carbon that can be subsequently modified by hydrologic alterations from land-use change and climate change. However, there are many uncertainties in predicting how carbon cycling and greenhouse gas emissions are altered by long-term changes in hydrology. Therefore, the goal of this study was to quantify how multi-decadal manipulations of water table (WT) levels affected carbon cycling (plant production and net ecosystem exchange from three eddy covariance towers) in a peatland complex modified by levee construction, which created a wetter area up-gradient of the levee (mean WT was 12.1 cm below the surface), a dry area below the levee (36.8 cm), and an adjacent reference site not affected by the levee (21.6 cm). We found that mean total plant production was greatest in the reference site (311.9 g C m−2 y−1), followed by the dry site (290.5 g C m−2 y−1), and lowest in the wet site (227.1 g C m−2 y−1). Net ecosystem exchange during the growing season was negative for all sites (sink), with the wet site having the greatest sink and the dry site having the lowest sink. Ecosystem respiration increased and CH4 emissions decreased with a decreasing WT level. This research demonstrates that human alteration of peatland WT levels can have long-term (>50 years) consequences on peatland carbon cycling.