The Xilingele grassland is the most typical of the Mongolian grasslands in terms of dominant species and major community characteristics such as cover, density, and primary productivity (Liu et al., 1987). Xilingele is a Mongolian word, meaning river [gele] on a ridge [xilin ]. The Xilingele grassland covers a lava tableland and has a relatively flat topography. The slightly wavy terrain, dotted by bare rock outcrops, forms a distinct steppe landscape. Without major rivers, the surface water system is poorly developed. Most of the few lakes and ponds are salty or alkaline. The groundwater table is usually deep, but may be as shallow as 3–5 m below the surface in localized depressions and interhill lowlands, where most herdsmen's yurts are found. Wells are a major water source for people and domestic animals.
The Xilingele grassland is located in the temperate semiarid climatic region. The climate is characterized by the alternation of dry summers and cold winters. The mean annual temperature is around 0°C, with an annual range of about 40°C (Figure 4-1). The frost-free season lasts from 120 to 140 days. The mean annual precipitation is between 250 and 350 mm, with a very uneven distribution over the year. In most years, up to 80% of the total precipitation falls from May to September, coinciding with the peak temperatures (Figure 4-1). This coincidence of high moisture and high temperature favors the growth of plants.
Spring is usually dry and windy, with high evaporation and low relative humidity. Although only 6–9% of the annual precipitation falls in winter