Vegetation Growth Variation in Relation to Topography in Horqin Sandy Land

Water availability is a major limiting factor for vegetation growth in semi-arid areas. Soil moisture availability is related to topography, which therefore, influences vegetation growth. To examine the response of vegetation growth to topography, we calculated an index of vegetation growth (GRNDVI) and analyzed its distribution along a topography index in Horqin Sandy Land, Inner Mongolia, China. Cropland growth improved and then deteriorated as topography increased, while wetness initially increased and then declined. In contrast, grassland growth initially declined and then improved with increasing topography, while wetness continuously declined. Grassland growth was affected by soil moisture and by different plant species. Cover and height of herbaceous species decreased from flat to hilltop while the cover and height of shrub species increased, especially those species with stronger drought tolerance. Different optimal land use scenarios were proposed based on water availability and topographic position. In the lowest areas, wetlands are proposed to promote natural habitat for aquatic plants and animals. In low areas, water facilities could be constructed and crops planted to supply food. In the middle area, grassland should be utilized to provide some pastures. In the upper and highest areas, drought tolerant shrubs should be planted to stabilize slopes and enhance native biodiversity and ecological integrity. The study could be used as a functional model to reduce desertification in semi-arid areas through optimizing land utilization, maintaining and enhancing ecological integrity and promoting sustainable development.