A model investigation of vegetation-atmosphere interactions on a millennial timescale

摘要

A terrestrial biosphere model with dynamic vegetation capability, IntegratedBiosphere Simulator (IBIS2), coupled to the NCAR Community Atmosphere Model(CAM2) is used to investigate the multiple climate-forest equilibrium statesof the climate system. A 1000-year control simulation and another 1000-yearland cover change simulation that consisted of global deforestation for 100 years followed by re-growth of forests for the subsequent 900 years wereperformed. After several centuries of interactive climate-vegetationdynamics, the land cover change simulation converged to essentially the sameclimate state as the control simulation. However, the climate system takesabout a millennium to reach the control forest state. In the absence of deepocean feedbacks in our model, the millennial time scale for converging tothe original climate state is dictated by long time scales of the vegetationdynamics in the northern high latitudes. Our idealized modeling studysuggests that the equilibrium state reached after complete globaldeforestation followed by re-growth of forests is unlikely to bedistinguishable from the control climate. The real world, however, couldhave multiple climate-forest states since our modeling study is unlikely tohave represented all the essential ecological processes (e.g. altered fireregimes, seed sources and seedling establishment dynamics) for there-establishment of major biomes.