The measurement and modelling of the carbon dioxide exchange at a highArctic site in Svalbard

摘要

Well-documented models of soil respiration and C-3 photosynthesis are combined to investigate the overall carbon dioxide balance of a high arctic polar semidesert site near Ny-Alesund, Svalbard. Measurements of carbon dioxide fluxes from an eddy correlation system and climate variables are used to calibrate this combined model for the snowmelt-summer period in 1995. Particular emphasis was put on modelling effectively the separate soil respiration and net photosynthesis of the moss/lichen, vascular plant and bare soil areas within the heterogeneous site, and ascertaining whether moss/lichen communities could be effectively modelled using a C-3 photosynthetic model. The calibrated model of 1995 data was subsequently tested in predictive mode against eddy correlation nux measurements recorded in 1996. The model is shown to simulate effectively both years and highlights the important role that the timing of snowmelt, summer precipitation and soil temperature has upon the overall carbon dioxide balance of this site. A previous conjecture by the author from the limited flux measurements that the investigated period in 1995 was an overall sink for carbon dioxide and that the same period in 1996 was an overall source of carbon dioxide is borne out by the model runs with 3.9 +/- 3.7 gC m(-2) being assimilated into the vegetation during the 1995 period and 5.0 +/- 3.3 gC m(-2) being returned to the atmosphere during the same period in 1996.