Study On The Spatial And Temporal Evolution And Driving Forces Of Vegetation Ecology In The Small Watershed Of The Loess Plateau

Vegetation plays an indispensable role in the ecosystem.In recent years,my country has taken some ecological measures to restore vegetation on the Loess Plateau,and has achieved certain results.Within a certain period of time,the natural environment has less impact on vegetation and human activities have a more direct impact.The Yunyan River Basin was selected as a typical area on the Loess Plateau,combined with 2000-2018 climate data and remote sensing data,using partial correlation analysis,land use transfer matrix,significance test,spatial Kriging interpolation and other methods to obtain the Yunyan River Basin Uniform vegetation index and spatio-temporal change characteristics of land use and climate change.Simultaneously analyze the influencing factors of vegetation growth including climate and human activities.Using surface energy balance equations to estimate watershed evapotranspiration,combined with remote sensing data on the net primary productivity of watershed ecosystems,to calculate,verify,and analyze the spatial and temporal variability of watershed ecosystem water use efficiency,and to study their changes and climate,vegetation,and humans Relevance of activities.The results show that:(1)The vegetation NDVI of the Yunyan River Basin has shown an increasing trend both in terms of seasonal and annual scales in recent years.From a spatial perspective,a large percentage shows a significant improvement trend;(2)The NDVI values and rainfall in the watershed are spatially positive The features of negative correlation coexist,but they are not significantly correlated(P<0.05);NDVI changes and temperature changes mainly show insignificant positive correlations,of which NDVI values and temperatures are positively correlated,accounting for 86.67%,while 13.33% of the areas are negative Correlation;(3)The land use types in the watershed have undergone relatively frequent conversions within 19 years,and the range of forest land and grassland has increased significantly.The conversion of different land use types in different periods has caused changes in vegetation NDVI at different scales;Larger,the WUE rising trend was significant before 2008(p<0.05).After 2008,WUE showed a weak downward trend,but this downward trend was not significant.The WUE in the study area is spatially opposite to the NDVI distribution,which is specifically high in the east and low in the southwest;(5)The WUE of the watershed is not significantly positively correlated with temperature(p<0.05),while the correlation with precipitation and NDVI is in The performance is different in different rainfall intervals.The rainfall range between water use efficiency and precipitation and NDVI is between 530 and 555 mm,and the negative correlation range is that the rainfall is greater than 555mm;the impact of the same precipitation on forest land WUE is less than that on cultivated land and grassland WUE.The sensitivity of cultivated land and grassland WUE to vegetation growth is positive,and the sensitivity of woodland water use efficiency to vegetation growth is negative.The sensitivity of grassland water use efficiency to precipitation and temperature is significantly higher than that of cultivated land and woodland.