THE POTENTIAL RESPONSE OF GLOBAL TERRESTRIAL CARBON STORAGE TO A CLIMATE-CHANGE

An analysis is undertaken to examine the potential impacts of a global climate change on patterns of potential terrestrial C storage and res ulting fluxes between terrestrial and atmospheric pools. A bioclimatic model relating the current distribution of vegetation to global clima te patterns is used to examine the potential impacts of a global clima te change on the global distribution of vegetation. Climate change sce narios are based on the predictions of two general circulation model e quilibrium simulations for a 2XCO2 atmosphere. Current estimates of C reserves in the vegetation types and associated soils are then used to calculate changes in potential terrestrial C storage under the two cl imate change scenarios. Results suggest a potential negative feedback to increasing atmospheric concentrations of CO2, with the potential fo r terrestrial C storage increasing under both scenarios. These results represent an equilibrium analysis, assuming the vegetation and soils have tracked the spatial changes in climate patterns. An approach for providing an estimate of the transient response between the two equili bria (i.e., current and 2XCO2 climates) is presented. The spatial tran sitions in vegetation predicted by the equilibrium analyses are classi fied as to the processes controlling the transition (eg., succession, dieback, species immigration). Estimates of the transfer rates related to these processes are then used to estimate the temporal dynamics of the vegetation/soils change and the associated C pools. Results sugge st that although the equilibrium analyses show an increased potential for C storage under the climate change, in the transient case the terr estrial surface acts as a source of CO2 over the first 50 to 100 yrs f ollowing climate change.