THE EFFECTS OF VEGETATION CHANGE ON REGIONAL CLIMATE Ⅰ:SIMULATION RESULTS

In the context of a regional climate model(RegCM2),simulation is undertaken of climatic effects of changed vegetation over China,reaching results which show that the increase in flood events over the Changjiang Huaihe River Valleys and the aggravation of North China drought are likely to be under the joint action of desertification of the northern grassland and southern degradation of evergreen broadleaf trees,the latter seeming to be the primary factor. Severe vegetation degeneration leach to a positive feedback between rainfall reduction and degradation with the consequence that the disaster expands steadily outward and the hit-area is difficult to turn back into farmland. In contrast,less heavy degeneration causes a negative feedback between deterioration and rainfall reduction. And the stricken sector is likely to reclaim when human damages are decreased or removed. However,degeneration strengthens surface runoff, allowing flood occurrence. Vegetation deterioration makes the climate even more inhospitable. On the other hand,experiments show that the vegetation enlargement of northern grassland will lead to a mild climate,responsible for precipitation reduction in the outer belts of afforestation,which is possible to cause newly-planted trees to die stepwise inward,a result that means the current climate in the grassy land does not seem to support a plan on large-scale afforestation there.