| Interaction between terrestrial ecosystem and climate system with the impact of human activities is one of the key scientific issues in the yield of global change research at the present time. In this paper, , the impact of future land use/cover change by using a regional integrated environmental model system (RIEMS) with the background of global warming on the summer climate in China were simulated. The dissertation consists of following three parts: Some climatic zones have shifted northward significantly during the last 50 years in China due to global warming and thus change of the climatic zones would induce vegetation belts to shift northward in the future. In the first part, the possible impacts of northward and southward shifts of actual and natural vegetation cover on Chinese summer climate were simulated respectively. The results show that the shift northward of actual vegetation could bring about the average temperature changes in summer with a cooling of above 0.3℃ in China and it could act on the regional warming tread as a reverse feedback: for a large portion of China to the south of 40 °N, the average temperature in summer decreases obviously, while the average rainfall increases in some of the southeast areas of China and there is a differential cyclone circulation over the southeast of China, which is favorable for the increase of water vapor over there. For the region to the north of 40 °N, the average temperature for summer increases obviously, while the average rainfall decreases and there is a differential anticyclone whose center located in eastern part of Mongolia. The simulation results of shift southward of actual vegetation in case of regional cooling trend show that the average temperature increases over 0.1℃ in China and it could also act on the regional cooling trend as a reverse feedback: for a large portion of China to the south of 40 °N, the average temperature in summer increases obviously, while the average precipitation decreases in the most areas of South China and there is a differential anticyclone circulation over there with its center located in the eastern part of southeast of China, which is unfavorable for the increase of water vapor over there. For the region to the north of 40 °N, the average temperature for summer has a small decrease, the average precipitation increase and there is a differential cyclone with its center located in eastern part of the Inner Mongolia Autonomous Region. The simulation results of potential and actual vegetation covers are similar in most respects, including the space distribution of the change of temperature, precipitation and atmospheric circulation in summer, however, human activities could enhance the reverse feedback of vegetation cover to the regional temperature change in most part of the region to the north of 35 °N and weaken the feedback in a relatively small areas of south of China. Comparing with the effects of glasshouse gases and aerosol on climate change, the feedback of the shift of vegetation belts to regional climate change could not be neglected in research of global change. In the second part, a set of numerical experiments are implemented to study the potential impacts of land use scenarios changes on the regional summer climate in 13 provinces of Northern China in the 2050 year by using RIEMS. These land use scenarios are the results of a System Dynamic model, which focuses on modeling land use scenarios change. After the different "what-if" scenarios controlled by GDP, population, market and technology advancement were built, six types of land use scenarios changes (namely, a, b, c, d, e and f) in the northern China in 2050 year were simulated. The results from RIEMS show that the six tpyes of 2050's land use scenarios changes could bring about local and nonlocal impacts on summer climate in different regions of northern China, especially in the arid/semi-arid region of Farming-Pastoral Zone, where the land use changes obviously too. Some measures in order to improve the ecological and environmental conditions such as afforestation, could have a favorable impact on the local climate: for the Northeast China and eastern part of Northwest China, scenario c is the most favorable scenario to alleviate the aridification owing to the most increase of woodland there with a decrease of thetemperature about 0.2℃ and a increase of the precipitation about 3%, whereas the temperature and rainfall have an inverse change in the South of North China. Comparing the different impacts of scenario c with d, it is not difficult to find that the scenario of which the economy development in higher speed and the demand for food supplies in higher speed is better than the scenario of which the economy development in slower speed and the demand for food supplies in slower speed. Finally, simulation is undertaken of climatic effects of desertification of grassland in the Eastern part of North China and disafforestation in the Southern part of China, and the climatic effects of several important surface physical parameters are compared with each other. Reaching results show that these two kinds of vegetation degradation may be stimulative factors to the increase trend of northern droughts and southern flood events, and the former seems to be the more important factor. It is confirmed that the arid/semi-arid region over Northern China is one of sensitive regions where the change of vegetation cover could cause more significant climatic effects than others. Different surface physical parameters influence on the regional summer climate in different ways. The single parameter act on the climate in local space scale mainly and the nonlocal climatic effects of land cover change should attribute to the integrated action of all parameters mostly.
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