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 (F-r) and an assimilatory (F-a) CO2 flux. The fit of the Arrhenius temperature response to F-r showed that F-r was generally higher at low groundwater tables. The fit of a hyperbolic irradiance response to F-a showed that F-r was also generally higher at low groundwater tables, more than compensating for higher F-r. 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 F-r 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.