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The impact of groundwater depth on the spatial variance of vegetation index in the Ordos Plateau, China: a semivariogram analysis
Journal of Hydrology ( IF 6.4 ) Pub Date : 2020-09-01 , DOI: 10.1016/j.jhydrol.2020.125096 Haoyue Zhang , Xu-Sheng Wang
Journal of Hydrology ( IF 6.4 ) Pub Date : 2020-09-01 , DOI: 10.1016/j.jhydrol.2020.125096 Haoyue Zhang , Xu-Sheng Wang
Abstract As important sensitive feedback of ecosystems, spatial distribution and patterns of vegetation can remarkably reflect eco-environmental conditions in arid and semiarid areas, where groundwater plays a significant role. The impact of groundwater depth (GD) on the spatial variance in remote-sensing vegetation index is highlighted in this study over the Ordos Plateau, China. The 250 m resolution mean annual Enhanced Vegetation Index (EVI) data are analyzed and compared to the same resolution data of altitude, air temperature, aridity index and GD. A linear regression analysis indicates a significant weak correlation between the EVI and the climatic and topographic controls at the regional scale. A semivariogram analysis is introduced to quantify the GD-dependent variance in the residual EVI (WEVI) filtered from this linear regression. The pixel-to-pixel dependency of WEVI on GD is nonlinear and significant only when GD is smaller than 10 m. The semivariance of WEVI increases with the lag distance and slightly fluctuates around the sill when the distance is sufficiently larger than 5 km. The sill of WEVI variance in the situation of GD ≤ 5 m is significantly higher than that in deeper groundwater situations. The semivariogram range of WEVI in the middle zone of the study area is lowest due to the lowest semivariogram range of GD. The nugget effect in the WEVI variance is weak but positively related to the nugget of GD variance when groundwater is shallow. High sensitivity of the vegetation cover to the shallow groundwater should be considered in the regulation of groundwater resources for ecological benefits.
更新日期：2020-09-01
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