EXCHANGE OF CARBON-DIOXIDE BY A DECIDUOUS FOREST - RESPONSE TO INTERANNUAL CLIMATE VARIABILITY

The annual net uptake of CO2 by a deciduous forest in New England vari ed from 1.4 to 2.8 metric tons of carbon per hectare between 1991 and 1995. Carbon sequestration was higher than average in 1991 because of increased photosynthesis and in 1995 because of decreased respiration. Interannual shifts in photosynthesis were associated with the timing of leaf expansion and senescence. Shifts in annual respiration were as sociated with anomalies in soil temperature, deep snow in winter, and drought in summer. If this ecosystem is typical of northern biomes, in terannual climate variations on seasonal time scales may modify annual CO2 exchange in the Northern Hemisphere by 1 gigaton of carbon or mor e each year.