Control of vegetation distribution: climate, geological substrate, and geomorphic factors. A case study of grassland in Ordos, Inner Mongolia, China

Many studies have dealt with the relationship between climate factors and vegetation, and some works confirmed the underlying substrate as an important factor in vegetation complexity and diversity in semiarid regions of northern China. However, the leading factor in vegetation distribution may vary with spatial or temporal scales. The objective of this study was to analyze the dominant factors in vegetation distribution and dynamics at large (regional) scales of space or time and at small (local) spatial scales. The results showed that temperature and precipitation were positively correlated with normalized difference vegetation index (NDVI) during a 20 year period (1980–2000) in the Ordos region. Both NDVI and average annual precipitation had the same trends, i.e., decreasing from east and southeast to west and northwest, which indicates the leading role of precipitation in vegetation distribution. At some locations, geologic faults with a well-developed clastic rock pervious layer are important effects on the distribution of vegetation cover in northern Ordos, near the border with the Kubuqi Desert. The lithology of bedrock greatly affects vegetation cover and distribution in the Mu Us Sandy Land area. There, a high percentage farmlands and grasslands with large NDVI values are mainly on low-permeability strata, such as the Quaternary Lake and alluvial deposits.