Carbon exchange of grazed pasture on a drained peat soil

Land-use changes have contributed to increased atmospheric CO2 concentrations. Conversion from natural peatlands to agricultural land has led to widespread subsidence of the peat surface caused by soil compaction and mineralization. To study the net ecosystem exchange of carbon (C) and the contribution of respiration to peat subsidence, eddy covariance measurements were made over pasture on a welldeveloped, drained peat soil from 22 May 2002 to 21 May 2003. The depth to the water table fluctuated between 0.02m in winter 2002 to 0.75m during late summer and early autumn 2003. Peat soil moisture content varied between 0.6 and 0.7m 3 m � 3 until the water table dropped below 0.5m, when moisture content reached 0.38m 3 m � 3 . Neither depth to water table nor soil moisture was found to have an effect on the rate of nighttime respiration (ranging from 0.4‐8.0lmolCO2m � 2 s � 1 in winter and summer, respectively). Most of the variance in night-time respiration was explained by changes in the 0.1m soil temperature (r 2 50.93). The highest values for daytime net ecosystem