Study On Spatial And Temporal Variation Of Vegetation Cover And Its Driving Factors

This paper takes Anhui Province as the research area, and the study period is 2000-2014 years. Applied methods include S-G filtering method, maximum value synthesis, Mean method, the trend analysis, stability analysis, dimidiate pixel model and correlation analysis. Using the MODIS NDVI data in 2000-2014 years on research area, the vector map of study region, monthly climate data set, Digital Elevation Model data and socio-economic statistical dat. Analysis the temporal and spatial variation characteristics of vegetation in Anhui province, and the response characteristics of vegetation NDVI to temperature, precipitation, topographic factors, population density and GDP changes. The main results are as follows:(1) 2000-2014 of NDVI in Anhui province showed a rising trend in annual, spring and autumn, and showed a slight downward trend in summer; The average vegetation coverage of Anhui province is fine, and it is gradually decreasing from north to south, in recent 15 years, the vegetation improvement was obvious, and the stability of NDVI was higher, and the stability was slightly worse in autumn and spring, in the annual, summer and autumn, the stability of the distribution of the gradient decreased from the south to the north; On the interannual scale, the vegetation cover is given priority to the moderate vegetation coverage and the lower vegetation coverage, the spatial distribution of vegetation coverage showed a trend of decreasing from north to south.(2) 2000-2014 of annual mean temperature in Anhui Province, showed a downward trend in annual, spring and summer, and the trend was increasing in autumn, precipitation showed an upward trend in the annual and seasonal; The correlation between vegetation NDVI and air temperature, precipitation in Anhui province is more significant, and the correlation with the temperature is better, vegetation NDVI basic synchronous response to changes in temperature, in addition to the Lag phase of summer is two months, the lag phase in the response of vegetation NDVI and precipitation change was 1 months, two months, 1 months and 0 months respectively in annual, spring, summer and autumn.(3) The vegetation NDVI in Anhui province was the biggest response to the same month change of temperature based on the station scale, the Lag period all was 0 months, The lag period of the response to the change of precipitation was 0-1 months, from the north to the South gradually increased trend; The maximum correlation coefficient of NDVI and temperature change response in Anhui province is on the whole, which is a gradual increasing trend from north to south, the maximum correlation coefficient with the change of precipitation showed the trend of increasing from the northeast to the southwest.(4) 2000-2014 of annual mean vegetation NDVI values in Anhui province increase with the increase of altitude, but when the altitude is greater than 1000 m, vegetation NDVI values decreased slightly, the NDVI growth rate of the vegetation at each altitude decreased with the increase of altitude; The average annual vegetation NDVI in Anhui province increased with the increase of slope gradient, with the increase of the grade of slope, the vegetation NDVI growth rate of the grade of slope became slower; The size of the average annual various aspect in Anhui province: sunny slope > half sunny slope > half shady slope > shady slope, each aspect to NDVI showed an upward trend, and the rate of rise was: sunny slope > half sunny slope > shady slope > half shady slope.(5) The main present positive correlation between NDVI and population density change response of each urban vegetation in Anhui province, spatial distribution on the performance of the north high south low distribution, the mostly present positive correlation of the changes in response to GDP, only 4 cities were negatively correlated, the spatial distribution is gradually decreasing from the northwest and southeast direction.