Predicting Ecosystem Responses to Elevated CO2 Concentrations

O ne of the many changes occurring in the biosphere due . to human activities is the increase in the carbon dioxide concentration of the atmosphere. This change is due both to the burning of fossil fuels, which is ejecting approximately 5-6 gT of carbon into the atmosphere yearly, and to deforestation, which may account for another 1~2 gT (Moore and Bolin 1986/87, Detwiler and Hall 1988). The preindustrial atmospheric CO2 concentration has been estimated at 280 cm3m-3 (Gammon et al. 1985), increasing to 350 cmm3 today (Keeling et al. 1989). This rise is an increase of 21 % in 170 years, with the most rapid increase occurring since 1950, when the concentration was 310 cm3m3 • We do not yet know how these changes are affecting terrestrial ecosystems, This ignorance is partly because we have relatively poor records of the functional and structural response of any ecosystem through