Surface CO2 exchange in an intensively managed peat pasture

Aerodynamic measurements of CO2 (F) and latent heat (lambda E) exchange were made in an intensively managed peat pasture during 2 consecutive years; the fetch was approximately 1.5 km. Surface conductance (g(s)) was calculated from the Penman-Monteith equation. F was split into a respiratory CO2 flux (F-r) and an assimilatory CO2 flux (F-a). F-r was non-linearly related to air temperature (T-a), revealing a distinct seasonal pattern in its value normalized to T-a. F-a was hyperbolically related to short-wave irradiance, the seasonal pattern of its maximum value compared to that of normalized F-r. T-a proved to be a major factor: F-a tended to maintain a positive response to T-a over much of the actual T-a range. Aerial vapour pressure deficit (D) was generally too low (<1 kPa) to have an effect on F-a.