| Weigan-Kuche river delta oasis is located in the arid region of northwest China.The soil salinization is quite serious while the ecological environment is fragile.It is of great significance to research the relationship between vegetation coverage and the spatial-temporal response of soil salinization,so as to protect and restore the regional ecological environment.Based on ETM/OLI remote sensing data in summer of 2001,2007,2013 and 2019,on the basis of field investigation and indoor experimental analysis,Using measured data to select the optimal model for inversion of vegetation coverage and soil salinization.On the basis of above mentioned,the response relationship between them has been analyzed,and the main conclusions are as follows:(1)The prediction accuracy of the segmented regression model and the FCD model of comprehensive segmentation advantages are both 79%.Comprehensively considering the decision coefficient,root mean square error and model universality,the FCD model combined with segmentation advantages is selected to conduct inversion the vegetation coverage in the Weigan-Kuche river delta oasis.In the past18 years,the area of extremely low coverage has shown a downward trend,while the areas of medium-high coverage and high coverage have generally shown an upward trend.The evolution of vegetation coverage is an increasing stage,with an average annual change of 0.793×10~4 hm~2.The spatial structure of vegetation coverage changes from simple to complex,and also from unstable to stable.Changes in temperature and increased precipitation have led to changes in vegetation coverage to some extent,however human activity is still the dominant factor of the great changes in regional vegetation coverage.(2)Compared with the feature space and multiple stepwise regression models,the partial least squares model constructed by introducing a variety of nonlinear transformation spectral indexes has high accuracy,thus this method is used to conduct inversion for the soil salinization in the Weigan-Kuche river delta oasis.From 2001 to 2019,the area of non-saline land increased continuously with a single dynamic attitude of 1.469%,while the area of lightly saline land and moderately saline land decreased with single dynamic attitudes of-1.864%and-0.769%,respectively.The area of severely saline land fluctuated greatly with a single dynamic attitude of 0.598%.The phenomenon of soil salinization has decreased,but the development stage has changed.The spatial structure of soil salinization changes from complex to simple.Human activities and natural factors such as topography,evapotranspiration,groundwater depth and so on affect the changes of soil salinization synergistically.(3)During the research period,there is negative correlation between vegetation coverage and soil salt content.Vegetation growing in desert areas have higher soil salt content and lower vegetation coverage,while the crops have lower soil salt content and higher vegetation coverage.Non-saline land is mainly planted with crops;mild salinization inhibits the growth of crops to a certain extent;the main vegetation cover on moderate and severe salinized land is salt tolerant vegetation.The correlation between vegetation coverage and soil salinization is more significant in transitional zones and desert areas mainly affected by natural environment,but less significant in oasis areas mainly affected by human activities.Under the influence of both human activities and natural environment,the spatial structure of vegetation coverage at different levels on diverse salinization lands has continued to become simple.Grasp the vegetation coverage and the spatial-temporal distribution of soil salinization and the characteristics of stability changes,On this basis,the response relationship between the two is analyzed,as well as providing reference basis for improving soil salinization according to local conditions and the sustainable development of agriculture. |
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