Indexed on: 09 Jan '07Published on: 09 Jan '07Published in: Climatic Change
This study explores the effects of atmospheric CO2 enrichment and climate change on soil moisture (Wr) and biome-level water limitation (LTA), using a dynamic global vegetation and water balance model forced by five different scenarios of change in temperature, precipitation, radiation, and atmospheric CO2 concentration, all based on the same IS92a emission scenario. LTA is defined as an index that quantifies the degree to which transpiration and photosynthesis are co-limited by soil water shortage (high values indicate low water limitation). Soil moisture decreases in many regions by 2071–2100 compared to 1961–1990, though the regional pattern of change differs substantially among the scenarios due primarily to differences in GCM-specific precipitation changes. In terms of LTA, ecosystems in northern temperate latitudes are at greatest risk of increasing water limitation, while in most other latitudes LTA tends to increase (but again varies the regional pattern of change among the scenarios). The frequently opposite direction of change in Wr and LTA suggests that decreases in Wr are not necessarily felt by actual vegetation, which is attributable mainly to the physiological vegetation response to elevated CO2. Without this beneficial effect, the sign of change in LTA would be reversed from predominantly positive to predominantly negative.