Research of vegetation cover variations in reservoir areas based on satellite remote sensing:A case study of Sanhekou Reservoir Area
[Objective]Reservoir constructions will disturb the vegetation in and around reservoir areas.To explore the impact of reservoir construction activities at different stages upon vegetation cover in reservoir areas,we proposed a method to quantify vege-tation cover changes based on remote sensing.[Methods]First,fractional vegetation cover was retrieved using the pixel binary model.Then,maximum value composite,differential method,buffer analysis,and Theil-Sen regression were applied to quantify vegetation changes according to different construction stages,distances from the dam site and elevation ranges.We chose the San-hekou Reservoir Area in Shaanxi Province as a case study.[Results]The result show that downstream vegetation cover as well as the proportion of high vegetation cover decreased significantly from 2014 to 2019,mainly caused by reservoir construction.From 2020 to 2022,upstream vegetation cover declined,and the proportion of low vegetation cover increased significantly,mainly due to reservoir impoundment.In addition,within a 1000-meter buffer zone of the reservoir area,the impact of reservoir construction on the vegetation cover is relatively great when the buffer distance is less than 400 meters,while it is relatively small when the buffer distance exceeds 400 meters.Reservoir impoundment leads to a decrease in both vegetation cover and vegetation uniformi-ty,which is more evident as the buffer distance decreases.[Conclusion]The impact of reservoir construction on downstream veg-etation cover is significant in the elevation range of 585 to 625 meters,while the impact of reservoir impoundment on vegetation cover in the near upstream section is significant in the elevation range of 555 to 625 meters.In the middle and far upstream sec-tions,the impact of reservoir impoundment on vegetation cover gradually intensifies as the elevation becomes lower.Vegetation cover variations detected by this method corresponds well to reservoir construction and reservoir impoundment,and the specific impact ranges of reservoir construction and impoundment on vegetation cover in the reservoir area are determined,which can serve as a reference for ecological protection of the reservoir area.
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