The Dual Response Of The Change Of Vegetation Coverage In Shaanxi Province To Climate Change And Human Activity

Vegetation is an important part of the ecosystem,and clarifying the change trend,distribution and driving mechanism of vegetation cover has important practical significance for ecological restoration and vegetation construction in the region.This article is based on the 2005 to 2018 MODIS-NDVI data set,meteorological data and related statistical data,using pixel dichotomy,unary linear regression trend analysis,standard deviation analysis,Hurst index,partial correlation analysis and residual analysis.Studying the characteristics of the temporal and spatial dynamic changes of vegetation coverage in Shaanxi Province in the past 14 years,and analyzing the correlation between the vegetation coverage changes in the study area in the past 14 years,meteorological factors and human activities,the main conclusions are as follows:(1)In the past 14 years,the overall vegetation coverage in Shaanxi Province has been good.Areas with medium or higher vegetation coverage accounted for 65.1%of the total area.There are obvious differences in spatial distribution.The northern area is lower than the central and southern areas,and the lower altitude areas are lower.In high-altitude mountain areas,the annual average vegetation coverage in Shaanxi Province is between 0.5-0.58 and fluctuates around 0.54 in terms of time.On the whole,the vegetation coverage in the study area has been relatively stable in the past 14 years.status.(2)From the perspective of the temporal and spatial evolution trend of vegetation coverage,the vegetation coverage of Shaanxi Province is showing an improvement as a whole.The improved area accounts for 55.843%of the total area of the province,covering an area of114813.21 km~2.The improved areas are mainly distributed in the loess plateau area in northern Shaanxi Province and southern Shaanxi.The volatility of vegetation coverage is not large,and the standard deviation is between 0-0.1739.The level of vegetation volatility is mainly affected by human activities.From the perspective of the sustainability of vegetation cover change,the Hurst index of Shaanxi Province is between 0.20 and 0.99,with an average value of 0.56,which has obvious spatial differences.Continuous change(69.89%)>anti-sustainable change(30.11%),the overall performance is continuous,indicating that the overall change in the future vegetation cover in Shaanxi Province will be continuous and stable;for urban areas with strong anti-sustainable changes,management and protection should be strengthened in the future development.(3)The annual average temperature in the past 14 years in Shaanxi has ranged from 3.28°C to16.15°C,with a difference of 12.87°C.The spatial distribution of the average annual temperature is roughly expressed as the existence of two high temperature zones with the Qinling Mountains as the dividing line.The high-temperature areas mainly appear in southern Shaanxi and Guanzhong areas,and the low-temperature areas appear in the Qinling Mountains,southeastern Shaanxi and northern Shaanxi.The average annual precipitation is between 179mm-1156mm,with a difference of 977mm,showing a gradual decrease in space from south to north,showing a linear distribution.The areas with more average annual precipitation are mainly distributed in the western and southern parts of Shaanxi.In the southern part of Guanzhong,the areas with lower average annual precipitation are mainly distributed in northern Shaanxi and eastern Guanzhong.From the slope of temperature and precipitation,the annual average temperature of the study area basically shows a downward trend,while the annual average precipitation changes.The trend shows a fluctuating trend of increasing and decreasing.(4)Vegetation coverage is mainly affected by moisture and heat conditions such as temperature and precipitation;on a seasonal scale,vegetation coverage changes and climate factors such as temperature and precipitation are mainly positively correlated.Among them,precipitation in winter,temperature in spring,and The partial correlation between precipitation and vegetation cover is weaker than that in other seasons.In terms of interannual variability,the partial correlation between precipitation and vegetation is not strong,which to a certain extent indicates that precipitation does not play a significant role in the growth process of vegetation,while the partial correlation between temperature and vegetation is relatively strong.The impact is greater in the process.(5)From 2005 to 2018,the impact of human activities on vegetation cover changes in Shaanxi Province gradually shifted to the direction of promotion,and the promotion effect continued to increase.The overall spatial distribution of residuals was mainly positive,and the area with positive residuals accounted for the province's total The area of 89.77%,the area with negative residual error accounted for 10.23%of the total area of the province.In Shaanxi,most areas of the residual trend are positive,of which 57.08%are the areas with a positive residual trend.Northern Shaanxi is the most widely distributed,followed by Southern Shaanxi and Guanzhong the least.The area with negative residual trend accounted for 1.92%,mainly distributed in Guanzhong Plain urban agglomeration,Hanzhong urban area and Ankang urban area.From spring to winter,the area where human activities promote vegetation growth increased from 19.87%to 38.23%,while the area where human activities inhibited vegetation growth gradually decreased,from 7.78%to 2.45%,the areas where the promotion of vegetation growth in spring,summer and autumn It is the most widely distributed in northern Shaanxi and changes with Yan'an as the center.The area of winter promotion is mainly in the Qinling area ofsouthern Shaanxi,expanding from Ningqiang in Hanzhong to Ankang and Shangluo,while from spring to winter,there is a development trend from north to south;The affected areas are concentrated in the Guanzhong area,and developed from northern Shaanxi to the Hanzhong Hantai area of southern Shaanxi to the Hanbin area of Ankang.Both the afforestation area and grain yield have had a positive effect on the change of vegetation cover.