Effect of drainage on CO2 exchange patterns in an intensively managed peat pasture

Eddy correlation measurements of CO2 exchange (F) were made in intensively managed peat pastures at 2 different groundwater tables during most of a growing season. F was separated into a respiratory (Fr) and an assimilatory (Fa) CO2 flux. The fit of the Arrhenius temperature response to Fr showed that Fr was generally higher at low groundwater tables. The fit of a hyperbolic irradiance response to Fa showed that Fa was also generally higher at low groundwater tables, more than compensating for higher Fr. The daily CO2 balance suggested that the low groundwater pasture was a larger CO2 sink or a smaller CO2 source than the high groundwater pasture during the measurement period. The difference in Fr between the groundwater tables was substantially less than the factor 2 difference in level of soil subsidence. This suggests that oxidization of soil organic matter was a relatively minor factor in soil subsidence.