(October to March), accumulated snow is important for winter water use and for regrowth of plants in spring. The year-to-year change in precipitation is as high as 30% in this region.

The major soil type in this region is chestnut, an alkaline soil with low organic matter content (less than 4%), poor fertility, and a marked calcic horizon. Other soils include chernozem, meadow, and saline types. The vegetation of the Xilingele grassland is typical steppe (dominated by Stipa grandis, Aneurolepidium chinense, Agropyron michnoi) and dry steppe (dominated by Stipa krylovii, Cleistogenes spuarrosa, and other bunchgrasses). Besides having distinct dominant species, other important differences between these two vegetational groups include the following: (1) forbs and rhizome grasses that are frequent in the typical steppe are poorly represented in the dry steppe; (2) the typical steppe develops in dark chestnut soils, the dry steppe in light chestnut soils; and (3) local climatic conditions are slightly drier and warmer in dry steppe than typical steppe (Li et al., 1988). With the increase in gravel and sand content of the soil, short semishrubs (e.g., Artemisia frigida) and shrubs (e.g., Caragana microphylla and other species of Caragana) become more important in species composition. The conspicuous Caragana gives the steppe a special physiognomy.

One of the most representative and best-preserved areas of the Xilingele grassland and of the whole Inner Mongolian Steppe is found in the Xilin River Basin (Li et al., 1988). This is also one of the best-studied grassland regions in China, with much background information having been accumulated during the past three decades. The Inner Mongolia Grassland Ecosystem Research Station, which includes the first grassland nature reserve in China, is located here. Several important projects related to UNESCO and the Man-and-the-Biosphere program have being carried out in this area. The Xilin River Basin extends from 43°26' to 44°39'N latitude, and from 115°32' to 117°12'E longitude, covering a total area of 10,786 km2 (1,078,600 hectares). The elevation of the region decreases from 1505.6 m atop the Daxinganling Mountains in the east to 902 m in the lower reaches of the Xilin River in the northwest. The growing season in the basin area is 150–160 days. Plants turn green in early or mid-April, enter their most active growing period in mid-to late May, and cease growing in middle or late September (see Figure 4-1). According to one recent survey, this region has 625 seed plants, belonging to 74 families and 291 genera.

Steppe communities are composed mainly of xeric, perennial herbaceous plants, occupying about 85% of the vegetated area of the Xilin River Basin. According to Li Bo et al. (1988), there are three natural steppe zones in the basin—meadow steppe, typical steppe, and dry steppe—although some researchers argue that the whole area is typical steppe. In the upper reaches of the Xilin River, meadow steppe, rich in both xeric grasses and mesic forbs, has developed on the fertile chernozem. In the middle reaches, with a decrease in elevation and precipitation,



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