The Inner Mongolia Autonomous Region (IMAR) occupies the center of China's northern tier, bounded on the east by Manchuria and on the west by Xinjiang. Covering nearly 1.2 million km2, Inner Mongolia accounts for 12.3% of China's total area but has less than 2% of its people. The region, which has less than 5 million hectares of cultivated land, or about 5% of China's total, boasts somewhere between one-quarter and one-third of the nation's grasslands. In 1989, the IMAR had nearly 87 million hectares of natural grassland, covering 70% of the region's total area and supporting more than 37 million large livestock, sheep, and goats. Animal products account for about 11% of the region's gross output (4.5 billion yuan in 1988). Only the far-western regions of Xinjiang and Tibet have comparable grazingland and livestock resources.

Eastern Inner Mongolia is dominated by the Mongolian Plateau, which extends southeastward to the Daxinganling Mountains that rise to average heights of 1000–2000 m. The Mongolian Plateau was uplifted to its current level of about 1000 m during the late Pleistocene. Many lakes that existed prior to this uplift have since disappeared, leaving desert areas—the source of extensive aeolian loess deposits to the southeast. In the central portion of Inner Mongolia the Yellow River makes a huge loop northward around the Ordos Plateau, where it forms local deltas and rich alluvial soil. The Ordos Plateau (approximately 1200-m elevation) to the south of the Yellow River loop was uplifted and tilted westward at the same time as the uplift of the Mongolian Plateau. The southern part of the Ordos is covered by thick aeolian loess deposits, alkali lakes, and extensive deserts. Further west, Inner Mongolia is dominated by the sandy and rocky deserts of the Alashan Plateau, which also rises to nearly 1000 m above sea level.

There is considerable variation in the composition and productivity of the Inner Mongolian grasslands. A strong rainfall gradient divides the region into a series of vegetation zones, from the wetter east to the drier west. Chinese scholars classify these grasslands into four (sometimes five) basic types (Li, 1962; Li et al., 1988; Liu, 1960; Liu et al., 1987; and Wang et al., 1979). "Meadow grassland" or "meadow steppe" [caodian caoyuan], at the eastern edge of Inner Mongolia on both sides of the Daxinganling Mountains and in neighboring Manchuria, is the tallest and most productive of the grassland types. Vegetation in this area includes the mountain plants, Filifolium sibiricum, Festuca ovina, and Stipa baicalensis, and at lower elevations, Aneurolepidium chinense. "Typical grassland" [dianxing caoyuan], a midheight, heavy-cover community, runs across the vast castanozem plateau west of the mountains and is dominated by Stipa grandis, Aneurolepidium chinense, and Agropyron michnoi. "Dry grassland" [ganhan caoyuan] is a shortgrass region further west, beyond the Yinshan Mountains, where a Stipa krylovii, S. bungeana, and Thy-

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