Dynamic Change Of Vegetation Cover And Its Response To Climatic Factors In Zulihe Basin Based On MODIS/NDVI Data

This paper selected the Zulihe Basin,which is located in the transition from semi-arid to arid areas,and selected the temperature and precipitation data of 32 meteorological stations in Gansu Province from 1956 to 2016,the MODIS/NDVI data set from 2000 to 2010,and the DEM image data of the river basin.The methods of spatial interpolation,one-dimensional linear trend line simulation and M-K non-parameter test were adopted.The characteristics of climate change in Zulihe Basin from 1956 to 2016,vegetation cover change from 2000 to 2010 and the response relationship between them were analyzed from regional level and grid level.The following key results have been achieved:(1)From 1956 to 2016,the average annual and seasonal temperature of the basin showed an upward trend.The average seasonal temperature increased by an increase in winter>autumn>spring>summer.The spatial distribution of annual and seasonal temperatures showed an increasing trend from Southeast to Northwest.The spatial distribution of temperature in the four seasons is higher in the South than in the North and central regions,and the area of most regions is on the rise.(2)From 1956 to 2016,the annual precipitation in this watershed showed a downward trend as a whole.except for winter,the seasonal precipitation decreased in spring,summer and autumn.The spatial distribution of annual and seasonal precipitation decreases from south to north in general,and the eastern area of annual precipitation goes from east to west in parallel,the central area increases from east to west,and the western area decreases from east to west.the area where the spatial distribution of seasonal precipitation tends to decline is much larger than that of the rising area.(3)The spatial distribution of vegetation:the vegetation distribution in this watershed is patchy mosaic,increasing in turn from north to south.The average vegetation coverage in many years is similar to that in many years.the spatial distribution of NDVI is increasing from north to south in four seasons.(4)The average annual NDVI is positively correlated with the horizontal change and spatial distribution of air temperature and precipitation.the vegetation grows faster with the increase of air temperature,and the increase of precipitation promotes the growth of vegetation,which indicates that the annual precipitation and air temperature are the main meteorological factors that affect the interannual dynamic change of vegetation in Zulihe Basin.Analysis of NDVI changes in the average annual and seasonal trends in the study area can be obtained,and the growth performance of vegetation in autumn is the best.In Zulihe Basin,the temperature and precipitation in autumn are the most suitable climatic conditions for vegetation growth.(5)Owing to the large-scale implementation of the project of returning farmland to forest and grass,NDVI value increased from 0.024 to 0.070 in 2000?2010,and the average change rate was 0.0046/a.NDVI is positively correlated with air temperature and precipitation,reaching a very significant level(a = 0.05).