The impact of groundwater depth on the spatial variance of vegetation index in the Erdos Plateau, China

Abstract

<p>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 Erdos Plateau, China. The 250 m resolution mean annual Enhanced Vegetation Index (EVI) data in the period 2000-2010 are analyzed and compared to the same resolution data of GD. It is indicated from the semivariogram that the correlation range of EVI (10-22 km) is close to the correlation range of GD (9-19 km) and both of them show a near to zero nugget. The semivariance of EVI generally decreases with the increasing GD from 0 m to 10 m, but the relationship could be disturbed by other factors. In the semiarid region of the study area where the aridity index falls between 3 and 5, the 98<sup>th</sup> percentile EVI which represents high density vegetation decreases nonlinearly with the increasing GD from 0 m to 7 m. In the arid region where the aridity index is higher than 5, EVI is relatively low and almost independent on groundwater. The 50<sup>th</sup> percentile EVI is generally not sensitive to GD, especially in the arid region. Thus, the spatial variance of vegetation is a synthetic result of the climatic and hydrogeological conditions, which should be considered in the regulation of groundwater resources at the regional scale for ecological benefits.</p>