Study On The Response Of Vegetation To Precipitation And Temperature Changes In The Inland River Basin Of Northwest

Over the past century of climate change on water resources,ecological environment and social and economic development,made a profound impact on both the growth of vegetation and distribution are greatly influenced by climate change,is a sensitive indicator of climate change,and closely related to climate change,vegetation and rainfall,temperature changes between the response is an important content of the scientific community,but most of the research is only qualitative response,There are few studies on the quantitative response relationship,especially in the northwest inland river basin.The northwest inland river basin has a vast area,covers a variety of climate types,complex landforms and landforms,and studies on climate change and vegetation change are typical and representative.To reveal the temporal and spatial variation rules and characteristics of climate factors and vegetation in the study area,and to analyze the response of vegetation to precipitation and temperature changes qualitatively and quantitatively,can not only enrich the research results on global climate change,but also provide scientific basis for future ecological environment improvement.In this paper,the Northwest Inland River Basin was used as the research area,using the monthly mean temperature,mean minimum temperature,mean maximum temperature,precipitation and the monthly normalized vegetation index(NDVI)data from 93 meteorological stations in the study area and its surrounding areas from 1951 to 2018,and the NDVI data from 2000 to 2018.Regression analysis,climate trend rate,pixel dichotomy model,correlation analysis,partial correlation analysis and other methods were used to fully reveal the spatiotemporal variation characteristics of climate factors and vegetation over the years,as well as the response relationship between qualitative and quantitative analysis.The main conclusions are as follows:1.The precipitation in most of the study area showed an increasing trend,and the spatial distribution pattern was more in the northwest and southeast,and less in the middle.The annual precipitation in the northern part of the Tianshan Mountains increased at the fastest rate(0.16mm/ year),but the change degree was not drastic.In Turpan Basin and its surrounding areas,the precipitation showed a downward trend(-0.04mm/ year)for many years,but the degree of change was more severe.On the whole,the spatial distribution pattern of precipitation from January to April and November to December in the study area was more in the northwest and less in the southeast.From May to October,the precipitation was more in the southeast and the northwest,but less in the rest areas.The precipitation increased at the fastest rate in summer,followed by autumn,and the slowest in spring.The precipitation in Delingha increased at the fastest rate in summer(1.15mm/ year),while the precipitation in Torrey showed an obvious less trend in spring(-0.28mm/ year).2.The three types of temperature in most of the study area showed an upward trend,with the average minimum temperature rising at the fastest rate(0.011?/ year),followed by the average maximum temperature(0.068?/ year),and the average minimum temperature rising at the slowest rate(0.047?/ year).The increase rate of the average minimum temperature near Qinghai Lake was the most obvious(0.075?/ year).The average maximum temperature in the vicinity of the Tarim Basin showed a slight decrease trend,but the decrease rate was not significant(-0.005?/ year).The three kinds of temperature in the north of the northern Tianshan Mountain and the south of the Qaidam Basin increased the fastest,and the degree of change was more drastic.The average temperature increased the fastest in summer(0.073?/ year),and the average maximum temperature and average minimum temperature increased the most in winter(0.027?/ year,0.061?/ year).The average temperature in the growing season increased at the rate of 0.029?/ year,the average minimum temperature and average maximum temperature increased at 0.036?/ year and0.022?/ year,respectively.3.From 2000 to 2018,NDVI in the study area showed an overall upward trend,with more NDVI in the northwest and southeast and less NDVI in the middle.It showed a single peak change trend in the year,reaching the annual maximum in August and the annual minimum in February.Vegetation growth in the north of the northern piedmont of the Tianshan Mountains gradually improved,while in the south of the northern piedmont of the Tianshan Mountains it showed a slight trend of decline.In the western part of the study area,the vegetation gradually became better from south to north,while in the eastern part,it gradually became better from north to south.4.From 2000 to 2018,the low,medium and low cover vegetation in the study area increased at the rates of 0.006/ year,0.0022/ year and 0.0008/ year,respectively,while the bare land area decreased rapidly(-0.009/ year).The medium and high vegetation coverage in the northern foothill of Tianshan Mountains and Qinghai Lake region increased slowly from April to August and reached the maximum,and gradually decreased from September to December.In the growing season,bare land showed a trend of rapid decrease(-0.0053/year),and the coverage of the other four types of vegetation showed an increasing trend.The low cover vegetation increased at the fastest rate(0.0027/ year),followed by the medium cover vegetation(0.0014/ year),and the high cover vegetation increased at the slowest rate.5.At the interannual scale,the area with significant positive correlation between vegetation and precipitation was the largest,while the area with positive(negative)correlation with the three types of temperature was not significantly different,indicating that the vegetation grew better with the increase of precipitation.At the monthly scale,the vegetation grew better with the increase of temperature,but too high temperature would inhibit the growth of vegetation.The area of partial correlation coefficients between vegetation and three types of air temperature in the north of northern Tianshan Mountain,the east of Hexi Corridor and the south of Tarim Basin passed the significant positive correlation test was larger.The vegetation is divided into five grades.When precipitation and temperature vary within a certain range,the vegetation responds to a certain range.For example,on the interannual scale,when precipitation,average temperature,average minimum temperature and average maximum temperature vary between 83.4?112.7mm,11.9?14.9?,1.9?5.3? and 9.06?12.3?,respectively,NDVI responses ranged from 0.105 to 0.11.