Effects Of Global Warming On Vegetation Pattern In Chinese Arid And Semi-arid Area

The global surface temperature has shown a significant upward trend since industrial revolution and the greenhouse effect caused by carbon dioxide is the main factor causing climate warming.Arid and semi-arid areas account for 41%of the global land area,carrying 38%of the world's population,and are extremely sensitive to climate change and human activities.On one hand,the increase of temperature and the decrease of precipitation will lead to the possibility of desertification in arid and semi-arid areas.On the other hand,the fertilization effect caused by carbon dioxide will promote the growth of vegetation in this area.So what is the response of ecosystems in arid and semi-arid areas to global warming?Regional vegetation ecosystem is the key to study the ecosystem in arid and semi-arid areas.As the"engineer of ecosystem",vegetation plays an important role in promoting the energy and material circulation of regional ecosystem,effectively preventing wind erosion,restraining desertification and regulating the stability of ecosystem.Vegetation pattern is a kind of regular spatial structure formed by vegetation macroscopically.It is the quantitative distribution of vegetation in time and space and the direct reflection of the impact of climate change on ecosystem.China is a country seriously affected by desertification.Therefore,study the vegetation pattern of vegetation ecosystem in arid and semi-arid areas of China can quantitatively depict the impact of climate change on vegetation ecosystem in arid and semi-arid areas of China,understand the impact and feedback mechanism and provide a certain basis for the healthy development of ecosystem and put forward effective desertification control policies.Based on infiltration feedback,a dynamic model of vegetation pattern is established to study the spatial distribution characteristics of vegetation pattern in arid and semi-arid regions of China and discuss the evolution trend of vegetation pattern under the background of warming.The main conclusions are followed:(1)Taking the area near Wuwei,Gansu Province as an example,based on the local temperature and precipitation factors,the precipitation is divided into surface water and groundwater.the climate vegetation dynamic model of plant biomass surface water groundwater is applied according to the infiltration mechanism.The results show that the distribution characteristics of the numerical pattern are consistent with the local actual situation,which indicates that the dynamic model considering climate change and warming factors can well describe the distribution structure of vegetation in this area.The results of numerical analysis show that under the current situation of carbon dioxide emissions,when the daily precipitation is less than 0.46mm and the annual average temperature is higher than 11?,the vegetation pattern will tend to desertification from point distribution;The formation process of stable pattern structure shows that,compared with temperature,precipitation is the key factor affecting the formation of vegetation pattern.When the concentration of carbon dioxide increases to a certain extent,its fertilizer effect will be reflected,which has a certain modulation effect on the growth of plants.(2)We take Wuwei,Gansu Province and Hulunbeier grassland which is sensitive to climate change and has serious desertification in recent years as example.Based on different carbon dioxide emission scenarios,the evolution trend of vegetation pattern under RCP2.6,RCP4.5 and RCP8.5 climate change scenarios is compared.The results show that the area around Wuwei tends to be oasis under RCP2.6 and RCP4.5 climate scenarios,and desertification under RCP8.5.The results show that RCP2.6 and RCP4.5 scenarios should be maintained,especially in RCP4.5 scenario,which fully reflects the modulation of carbon dioxide fertilization effect.Even the increase of temperature and the decrease of precipitation cannot prevent the growth of vegetation in the region.In Hulunbuir grassland,the change of climate elements and the actual decrease of vegetation in recent years all show that the region is sensitive to climate change and desertification is serious.The evolution of vegetation pattern under current,RCP4.5 and RCP8.5 climate scenarios shows that the area tends to desertification especially fast in Current scenario.It is mainly due to the regulation of carbon dioxide fertilization under RCP4.5 and RCP8.5,which makes the growth of plants increase,but the increase of temperature and the decrease of precipitation in the later stage make desertification inevitable.RCP2.6 scenario still shows a good trend of ecosystem development.