Responses Of Different Vegetation Types To Climate Change And Monsoon Systems In Southwest China

Southwest China is located in the monsoon-affected intersection with complex terrains and fragile ecosystems.The growth of vegetation is affected by climate and monsoon changes.This paper identified areas with significant climate change in Southwest China,discussed the characteristics and differences of different types of vegetation in response to climate and monsoon changes,and divided areas where vegetation was significantly affected by the monsoon using CN05 gridded climate data set(1961-2016),NCEP/NCAR reanalysis wind field data(1948-2018),GIMMS NDVI data(1982-2015)and Land Cover data,applying correlation analysis,catastrophe analysis,students' t-test.The results show that:(1)During 1961-2016,the temperature in Southwest China increased by 0.24?/10 a.The abrupt change occurred in the 1990 s while in the 2000 s was the period time with the largest increase.There were volatile changes in moisture,a relatively high level was in the 1990 s.Spatially,the study area was divided into seven areas which climatic variables changed significantly,including one area with rapidly increasing temperatures(H-T),one area which getting wet and hot(W-H),one area with extremely wet and warmer trends(EW-W),two areas which getting dry and warm(D-W-?/?),and two areas with no significant changes in climate(N-C-?/?).(2)During 1982-2015,the East Asian summer monsoon index(EAMI)and the Plateau summer monsoon(IPM)changed non-significantly,while the South Asian summer monsoon index(SAMI)showed a trend with 0.66/10 a.In a long time periods(1948-2018),the EAMI,the SAMI and the IPM showed the trend of-0.36/10 a,-0.27/10 a and 0.18/10 a,and had an abrupt change in 1976,1990 and 1970,respectively.(3)During 1982-2015,the annual average NDVI and maximum NDVI of broadleaf forests,mixed forests,and evergreen monsoon forests increased by 0.005 to 0.015/10 a,while the average NDVI of the evergreen monsoon forests in summer increased by 0.012/10 a.From the perspective of the characteristics of the interannual changes of vegetation: firstly,the correlation between vegetation and variables characterizing temperature changes was stronger than the correlation between vegetation and variables characterizing water changes.Secondly,mixed forests had the strongest correlation and lag correlations with climate factors,followed by grasslands and broadleaf forests in summer.Finally,evergreen monsoon forests had no significant correlation with the variables that characterize changes in temperature and water.(4)In the west of the study area,the plateau summer monsoon had a significantly positively correlated with vegetation.The correlation between mixed forests and plateau monsoon was stronger,grasslands had the most obvious difference between strong/weak monsoon years,and broadleaf forests had the weakest correlation with plateau monsoon.In the western part of the study area,the vegetation was mainly affected by the South Asian monsoon.The vegetation in the west(east)of 105°E had significantly positively(negatively)correlation with the South Asian monsoon.The response between Various vegetation types and monsoon from strong to weak was followed by broadleaf forests,grasslands and mixed forests.