The Change Of Ecological Characteristics Of Mountainous Areas Of Southwest China And Its Relationship With Human Activities

Since the Western Development Program launched in the 20th century,the economy and tourismin Southwest China have developed rapidly.In 2017,the economic growth rates of Guizhou,Tibet,and Yunnan were top three in China.The economic growth rate of Guizhou has remained in top three for 27consecutive quarters since the first quarter of 2011.Only Guizhou and Tibet maintain a gowth rate larger than 10 among all the provinces.Besides,the economic growth rates of Sichuan,Chongqing,Guangxi,and Qinghai are also significantly higher than the national level,all of them exceeding 7%.This shows that there was a rapid economic growth in Southwest China.In the future,the increasing trend of economic growth will stillkeep on.Southwest China is located on the second stage of topography.The land surface is undulating,and the elevation of most areas is between 1500 and 2000 meters.The mountainous areas cover a wide area and span the the Qinghai-Tibet Plateau and the Yun-Gui Plateauwhich belongs to the world's high altitude areas.The ecosystem is fragile in Southwest China,but its value is quite importan since it is anecological barrier of South China.However,during the historical period,intense human activities did serious damage to ecosystems in some areas,which causing a decrease of ecosystem service functions.A series of ecological problems came up such as vegetation degradation,land desertification and soil erosion.In recent years,the government has reinforced environment protection and improvement.At the same time,the rapid development of urbanization and economy played an important positive role in the restoration of the ecosystem in Southwest China.However,at present,we do not have a clear understanding of the overall situation of the ecological environment and the development path of ecological restoration in Southwest China.This study is based on MODIS-NDVI,MODIS-NPP,land cover data from European SpaceAgency and statistical yearbook data from 2000 to 2015.With the help of ArcGIS and SPSS,this study applied linear regression method,land-use transfer matrix method,and multiple linear regression method to analyze the changes in the ecological characteristics and the impact of human activities on it.The main conclusions of this study are as follows:1.The NDVI in Southwest China increasedsharply,but the regional differences were significant.?1?From 2000 to 2015,the overall NDVI of Southwest China and the NDVI of forest-grasslandboth showed an incresingtrend.The overall rate was 0.0017/a and the rate of forest-grassland was 0.0014/a.The average NDVI values between years in Southwest differ greatly spatially,showing a decreasing trend from northwest to southeast.The NDVI increasing areas took up38.02%of the total area of Southwest China.The area with no significant changes accounted for 57.81%and the reducing area took up 4.17%.From 2000 to 2015,the overall NDVI decreased along with the increase of altitude,and the rate was0.1248/km.?2?The change rates of NDVI in different vegetation types in Southwest China were as follows:grassland>cultivated vegetation>coniferous forest>shrub>steppe>swamp>desert>alpine vegetation>meadow>broad-leaved forest>other>coniferous and broad-leaved mixed forest.2.The NPP in Southwest China shows a flucutaing rising trend?1?From 2000 to 2015,the NPP in Southwest China showed a fluctuating risingtrend with a rateof 2.34gC·m^-2yr^-1/a,and the rate of forest-grassland was 2.66 gC·m^-2yr^-1/a.The spatial distribution of averageNPP is low in the northwest and high in the southeast.The area with increased NPP accounts for21.89%of the total area in Southwest China,the area with no significant change accounts for 66.72%and area with decreasing NPP accounts for 11.45%.The NPP value showed a trend of firstly increasing and then decreasing along with the increasing altitude.The overall decreasing rate was 126.966 gC·m^-2yr^-1/a.?2?The change rates of NPP in different vegetation types were as follows:grassland>cultivatedvegetation>coniferous forest>shrub>mixed coniferous and broad-leaved forest>swamp>meadow>broad-leaved forest>others>steppe>alpine vegetation>desert.3.The land cover in Southwest China has changed significantly?1?From 2000 to 2015,the area of cultivated land,grassland and other land in SouthwestChinadecreased.Among them,the area of cultivated land reduced mostwith a loss of 781,200 hectares in 16years.The area of forest,construction land and wetland increased.Among which,the growth rate of construction land was the largest.The area of construction land increased by three times during 16 years.Cultivated land was mainly converted to forest?46.05%?and construction land?31.68%?.Forestwas mainly converted to cultivated land?68.17%?.Grassland was mainly converted to cultivated land?38.82%?and other land?41.46%?.Wetland was mainly converted to forest?54.46%?.Other land was mainly converted to forest?60.00%?and grassland?30.68%?.?2?From 2000 to 2015,the changing areas of land cover changewere mainly concentrated in thealpine meadow area of Naqu in northern Tibet,Wenchuan earthquake area in Sichuan Basin,nature reserve area in southwestern Yunnan,developed tourism area in Guilin,Guangxi and land desertification area in Bijie,Guizhou.In these areas,human activities have an important impact on the changes of land cover.4.The phenomenon of forest transition in Southwest ChinaThere was an“U”relationship between the changes of forest area and industrial output value percapita.At the county level,forest transition was exited inSouthwest China.The increase of changes in meat production have a significant negative effect on the changes in forest area?significant level,0.05?.The increase of the rural population has a significant positive effect on the changes of forest land area?significant level of 0.1?.The increase of temperature has a positive effect on the changesof forest area?significant level of 0.01?.Elevation and precipitation have no significant impact on the changes of forest area.