Study On Differences Of Vegetation Coverage Under Different Landforms In Nearly Similar Climate Units On The Loess Plateau

The implementation of returning farmland to forest or grass has significantly increased the vegetation cover in the Loess Plateau,but the effect of the policy is different in each region.By exploring the differences of vegetation coverage of different land forms in different regions under similar climatic conditions in the Loess Plateau,it is helpful to reveal the differences of comprehensive characteristics of vegetation in the Loess Plateau,understand the changes of vegetation coverage in similar units of the Loess Plateau in a more detailed manner,and accumulate scientific knowledge for the evaluation of ecological governance effectiveness and future governance.Therefore,the meteorological station data of the Loess Plateau are used to divide similar climate units.Based on the NDVI data of sentry 2 and the DEM data of ALOS satellite,different elevation,slope and aspect conditions are superimposed to divide similar climate units into different terrain conditions to study the difference of vegetation coverage.The main conclusions of this study are as follows:(1)In different is precipitation zone,under different slope conditions,from north to south,the change trend of NDVI area proportion of different grades in each precipitation zone is the same.When the gradient is greater than 5 °,along the gradient of different equal precipitation zones,the more precipitation,the area proportion of NDVI < 0.4gradually decreases,and the area proportion of NDVI ≥ 0.4 gradually increases,indicating that within this gradient range,the vegetation growth status is getting better and better with the increase of precipitation.Affected by the landforms of different zones,NDVI < 0.4 is intensively distributed in the precipitation zone closer to the north and uniformly distributed in the precipitation zone closer to the south.At the same time,the proportion of NDVI ≥ 0.4 area increases.Under the condition of different slope directions,along the gradient of different equal precipitation zones,the more precipitation,the area proportion of NDVI < 0.4 gradually decreases,and the area proportion of NDVI≥ 0.4 gradually increases.At the same time,the area proportion of NDVI ≥ 0.4increases with the increase of precipitation in equal precipitation zones,indicating that within this slope direction,the vegetation growth status is getting better and better with the increase of precipitation.In the sunny slope,the proportion of NDVI < 0.4 is greater than that of NDVI ≥ 0.4,the shady slope is just the opposite,indicating that the vegetation growth on the sunny slope is not as good as that on the shady slope.(2)In different isotherm zones,when the slope is different,the areas indicated by NDVI < 0.4 are mainly in each buffer zone,and are widely distributed in various places in the buffer zone.The NDVI distribution of different slopes is greatly affected by the local landform.The lower the slope,the more northerly the geographical location,and the larger and concentrated low vegetation coverage,indicating that within this slope range,the vegetation coverage increases with the increase of precipitation.Under different slope directions,NDVI < 0.4 is dominant in each buffer zone,which is widely distributed in the buffer zone.The area with NDVI ≥ 0.4 accounts for a relatively low proportion,and the vegetation coverage of corresponding grades is concentrated in one area.(3)In the same unit,with the same elevation and different slope directions,there is little change of the vegetation coverage of each grade on the yin-yang slope,and the distribution is relatively uniform;When the slope aspect is the same and the elevation is different,the distribution of NDVI area in each grade is similar,and the lower the elevation,the better the vegetation growth;Under the same elevation conditions and different slopes,the proportion of NDVI area of each grade varies greatly,and the vegetation growth condition is better when the slope is low.