Guanzhong Area Of ​​vegetation Cover Change And Its Main Driving Factor Analysis

Vegetation plays an important role in globe changing and terrestrial ecosystem. It is not only according to vegetation protecting, but also playing an important role in cycling of globe energy and stabling of global climate for research of vegetation coverage and its main driving factors. Guanzhong Plain is located north of the Qinling Mountains, south of the Loess Plateau, includes Qinling Mountains, Guanzhong Plain and the Loess Plateau. It has complex terrain and various types of vegetation in Guanzhong area. It has great significance on the protection of the forests and high standard farmland for the research of vegetation coverage.In this paper, the SPOT NDVI data, DEM data, meteorological data, population data, GDP data and land coverage data are used to reveal the characteristic of vegetation cover and, analyses the main driving factors of vegetation cover change and forecast the trend of vegetation in research area based on remote sensing and geographic information system. Here are the main conclusions:(1)The condition of vegetation cover is good from1999～2010in Guanzhong Plain, the value of NDVI is highest in the northern slope of Qinling, lowest in urban area. The value of NDVI has a progressively decreasing from south to north. In the Study Period, the growth rate of NDVI is5%/10a. It has steadily increased trend of vegetation cover over12years, the mild improvement area accounted for70.39%, the basic constant region accounted for24.77%, the degradation area is concentrated in the urban area, accounted for only2.07%.(2)DEM data is used by analyzing the influence on vegetation cover from topography in elevation, slope and aspect. The vegetation cover shows improving trend in320m～3400m, on the contrary, the vegetation cover over3400m has a degradation trend. The slope value of NDVI increased rapidly with the increasing slope in0°～6°; the slope value of NDVI increased stably with the increasing slope in6°～15°;the vegetation cover increased slowly in15°～25°; slope value of NDVI decreased rapidly above25°. The slope value of NDVI in sunny slope was beyond shady slope, shady vegetation is more active than sunny.(3)On the whole, the temperature in Guanzhong area is increasing in the past12years, the temperature increased at a rate of0.23℃/10a, through the inspection of the significant level of0.01. The trend of precipitation was fluctuating in the past12years, but it was increasing overall. The correlation between NDVI and temperature is better, which compared significantly with a positive correlation accounted for33.26%; In general, NDVI and precipitation showing a weak positive correlation, weak positive related pixel accounted for54%, better significant positive correlation pixel accounted for13.01%.NDVI and the average annual temperature correlated negatively in the north of Wei river, but it has both positive and negative correlation between NDVI and annual precipitation; positive correlation coefficient is large between NDVI and average annual temperature, but it is on the contrary between NDVI and annual precipitation; the correlation coefficient of NDVI and average annual temperature higher than annual precipitation. The situation demonstrated that correlation between temperature and precipitation on vegetation is not synchronized.(4)Distribution of population in Guanzhong area has the characteristic of low-density. The area where population is less than100/km2is25958km2, accounting for46.82%. The area where population is more than5000/km2is441km2, accounting for only0.79%. Vegetation coverage decreased with the increasing population in Guanzhong area, the increasing rate of vegetation being smaller at the population of0～5000.When the population is more than5000, the vegetation cover has the trend of degradation. The high value of GDP is mainly concentrated in the area of the Weihe River valley, the highest GDP in Xi’an and its surrounding areas, NDVI decreases when the GDP increase.(5)The mean NDVI of each land use type is:grassland>woodland>plough>water> unutilized land>building land. Vegetation coverage of building is worst, the grassland is the best. The variation trend of land cover is:grassland>woodland>plough>water> unutilized>building land, increasing tendency of grass land is prominent, but it has degradation trend on building land.(6)Using correlation analysis and establishing a multiple linear regression model to get the influence of each factor. Elevation has the greatest impact on vegetation; followed by GDP, temperature, land use degree; population, slope, precipitation third; aspect is the minimal factor. The vegetation in the next10years,20years and30years are showing the trend of improvement. In the next30years, the growth rate of NDVI in each city is greater than0.049/10a.