Response Of Vegetation To Climate Change In Karst Area Of Central Yunnan

Climate change is the number one environmental problem faced by human beings today.Under the background of climate change,there are significant differences in response modes of different vegetation types.Therefore,exploring the response mechanism of vegetation to climate change will provide theoretical support for vegetation restoration and reconstruction.In this paper,seven typical vegetation sample areas of Shilin County in central Yunnan karst area are taken as the research object.The field practice investigation method,mathematical analysis method,' 3S 'technology and other methods are used.Combined with the existing meteorological original data,the response mechanism and process of vegetation to climate change are analyzed,and the stability of different vegetation types to cope with climate change is studied,so as to provide scientific and technological support for rocky desertification control,ecological restoration and reconstruction and water source construction in central Yunnan karst area.The results are as follows:(1)The average annual temperature in Shilin County from 1988 to 2017 was16.6 °C.1998 is the year of abrupt temperature change,and the temperature has been increasing since 1998,and there is a global periodic change in temperature from 14 to21 a.The average annual precipitation from 1988 to 2017 was 914.15 mm,fluctuated between 550.6 mm and 1362.2 mm,showing a downward trend overall,with a decline rate of-11.5 mm / 10 a.The abrupt change of precipitation series occurred in 2008,and the 10-20 a period oscillation was the strongest,with a global characteristic.(2)The NDVI values of Changhu,Guishan,Yuehu,Heilongtan,Tangzishan,Guanshan Reservoir and Yunnan pine forest from 1988 to 2017 were 0.29,0.32,0.26,0.29,0.17,0.28 and 0.27,respectively.The NDVI values of Yuehu,Tangzishan and Guishan showed an overall upward trend during the study period,and the rising rates were 0.015 / 10 a,0.006 / 10 a and 0.006 / 10 a,respectively.Changhu,Heilongtan,Guanshan Reservoir and Yunnan pine forest showed a downward trend,and the decline rates were-0.011 / 10 a,-0.005 / 10 a,-0.007 / 10 a and-0.005 / 10 a,respectively.(3)The highest vegetation coverage,moderate precipitation and temperature at altitude of 1800-1900 m are conducive to the growth and development of vegetation;8-15 degrees gentle slope,rich in soil mineral nutrients,while storing plant water;On the semi sunny slope,light and water are the most suitable,which can provide more favorable conditions for the growth and development of vegetation itself.(4)From the difference of different vegetation types,the vegetation change of evergreen broad-leaved forest is mainly affected by precipitation factors.The NDVI value of vegetation is high with more precipitation.The temperature has a great contribution to the vegetation change of secondary vegetation,coniferous forest and rocky desertification shrub,and the NDVI value of vegetation increases with the increase of temperature.The vegetation change in growing season was mainly positively correlated with precipitation and temperature from April to June.(5)The lake wetland has obvious influence on the change of lakeshore vegetation.By comparing the stability of seven vegetation areas,Changhu <Heilongtan < Guishan < Yuehu < Guanshan Reservoir < Songlin Yunnan <Tangzishan.Combined with the actual investigation,it is found that Tangzi Mountain,Guishan Mountain and Yunnan pine forest are far away from the lake,the average annual NDVI value of vegetation is small,the CV value is large,and the NDVI change is greatly affected by human activities.On the contrary,the Changhu,Heilongtan and Guanshan reservoirs are close to the lake,and the NDVI value of vegetation is high and stable.On the one hand,it is the effect of temperature and precipitation;on the other hand,it is the effect of lake storage.Close to the lake,the air humidity and soil moisture in the forest can be maintained,and the transpiration of vegetation can be reduced.In dry season,it can also supply the water needed for vegetation growth and development.The secondary vegetation is mainly planted around the lake in Yuehu area,and the NDVI value of vegetation shows a significant upward trend,indicating that the overall restoration of vegetation in this area is relatively good.At the same time,this also indicates that lake wetlands have a significant impact on the change of lakeshore vegetation.