Long-term observation of the atmospheric exchange of CO2 with a temperate deciduous forest in southern Ontario, Canada

This paper reports the results of the analysis of eddy covariance CO2 data obtained at a successional forest of maple and aspen at Camp Borden in southern Ontario, Canada, between July 1995 and December 1997. The Michaelis-Menton model explains more than 50-65 percent of the observed variance of the daytime net ecosystem carbon exchange (NEE) during the growing season; leaf wetness appears to be an important variable contributing to the remaining variance. The whole-ecosystem respiration rate as a function of the 5-cm soil temperature shows a seasonal 'hysteresis' (higher rate in the later part of the year), suggesting a nonnegligible contribution by deep soil/roots and the influence of litter age. There is evidence of photosynthetic activities immediately after the spring snowmelt/soil warming, but the daily NEE did not switch sign till about 40 days later. (Author)