| Land is the basis for human survival,due to climate change and human activities and other comprehensive factors,land degradation is constantly intensifying,making the ecological environment continue to deteriorate,bringing huge hidden dangers to China’s social and economic development.Taking Shaanxi Province as the research area,using CASA model,univariate linear regression,correlation analysis and other methods,using NDVI,vegetation cover,meteorology and other sequence data from 2000 to 2020 in Shaanxi Province,the temporal and spatial changes of vegetation net primary productivity（NPP）and vegetation precipitation utilization rate（RUE）in Shaanxi Province in the past 20 years were studied,and the characteristics of the trend changes of the two were synthesized to determine the characteristics and types of land degradation in Shaanxi Province,and the degradation cause analysis was carried out by using the geographic detector model.The results showed that:（1）Shaanxi Province from 2000 to 2020,the range of multi-year NPP mean is 0-1114.38g C.m-2.a-1,the spatial distribution law of NPP in Shaanxi Province is from south to north,gradually decreasing,NPP has a downward trend in the area,economic activities are hot,in the past 20 years,the change law of its NPP in the amount of fluctuations rises,indicating that the overall vegetation quality of Shaanxi Province is evolving,and the overall improvement of its ecological environment.The mean multi-year RUE in Shaanxi Province ranged from 0-1.82,with the lowest value occurring in urban centers and the highest value occurring in mountainous evergreen broadleaf forests and their mixed deciduous broadleaved forests.The distribution law of RUE in Shaanxi Province is that except for the urban agglomeration area of Guanzhong Province,it shows the distribution law of middle height and gradually decreasing to both sides,and RUE integrates vegetation NPP and precipitation data,and its distribution law coincides with the steep terrain on both sides of the middle flat side of Shaanxi Province.（2）The changes of NPP and RUE trends in Shaanxi Province are:the average slope of NPP trend in Shaanxi Province is 8.23,and the ecological environment of Shaanxi Province is improving on the whole.The area with a significant decrease trend of NPP was 563.5km2,the area with no significant decrease was 1056.75km2,the area of the area with the unchanged NPP was 2426.5 km2,the area of NPP with a nonsignificant increasing trend was 7044.25 km2,and the area with a significant increasing trend was 205040.5km2.The average RUE slope slope in Shaanxi Province was 0.0097,indicating that the vegetation precipitation utilization rate in Shaanxi Province showed a weak upward trend as a whole.The area of RUE with a significant decreasing trend is 447.75 km2,the area with no significant decrease is 9643 km2,the area of RUE unchanged area is 2426.5 km2,the area with an insignificant increase trend is 89563.75km2,and the area with a significant increasing trend is 114140.5 km2.（3）The overall land change situation in Shaanxi Province is improved.The areas of severe land degradation in Shaanxi Province are mainly concentrated in the urban expansion areas of Guanzhong and the areas of minor degradation are mainly concentrated in southern Shaanxi.The overall degradation distribution law is that northern Shaanxi is improved as a whole,with more severely degraded areas in Guanzhong and more slight degradation areas in southern Shaanxi.The area of severe land degradation in Shaanxi Province was 1634.25 km2,the area of land slightly degraded was 2236.75 km2,the area of unchanged area was 2426.5 km2,the area of slightly improved area was 6295.75 km2,and the area of significant improvement was the largest,which was 203628.25 km2.（4）The types of land degradation in Shaanxi Province in this study were as follows:the area of land desertification was 6.74 km2,the area of soil erosion was 218.89 km2,the area of salinized land was 484.35 km2,the area of land pollution was 555.04 km2,the area of land damage was 709.30 km2,the area of land impoverishment was 1676.91 km2,and the land area of unchanged was 2272.20 km2.The land area of the slight improvement is 5994.36 km2,and the land area of the significant improvement is 192983.32 km2.（5）The results of geographic detector showed that the land use q value in 2000 was 0.082and the q value in 2020 was 0.136,and the P value of both was 0,which was very significant.The q-value of XTULI2000∩XTULI2020 was 0.1698,indicating that the influence weight of human factors on land degradation was 16.89%. |
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