ABSTRACT
Introduction to Steppe Ecosystems in China . . . . . . . . . . . . . . . . . . . . . . . . . 316 Brief Account of Steppe Ecosystems . . . . . . . . . . . . . . . . . . . . . . . . . . 316 Main Types of Steppe Ecosystems and Their Features . . . . . . . . . . . 316
Temperate Meadow Steppe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 317 Temperate Typical Steppe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 317 Temperate Desert Steppe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 318
Effect of Grazing on Soil Properties in Steppe Ecosystems . . . . . . . . . . . . . 318 Effect of Grazing on Soil Physical Properties . . . . . . . . . . . . . . . . . . . 319
Effect on Soil Bulk Density . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 319 Effect on Capillary Water Content. . . . . . . . . . . . . . . . . . . . . . . . 319 Effect on Soil Hardness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 319 Effect on Soil Mechanical Composition . . . . . . . . . . . . . . . . . . . 319 Effect on Soil Microgranule and Structure . . . . . . . . . . . . . . . . . 322 Effect on Clay Minerals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 323 Effect on Submicroscopic Characters . . . . . . . . . . . . . . . . . . . . . 324
Effect of Grazing on Soil Nutrient Content . . . . . . . . . . . . . . . . . . . . 325 Effect on Organic Matter (OM), Total Nitrogen, (TN), and
Total Phosphorous (TP) Contents . . . . . . . . . . . . . . . . . . . . . . 325 Effect on Soil Available Nutrient Contents. . . . . . . . . . . . . . . . . 327
Effect on Soil Humus Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 327 Composition of Soil Humus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 327 Elemental Composition of Humus . . . . . . . . . . . . . . . . . . . . . . . 329 Oxygen-contained Function Groups (OFGs) . . . . . . . . . . . . . . . 329
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333
INTRODUCTION TO STEPPE ECOSYSTEMS IN CHINA
Brief Account of Steppe Ecosystems
Grassland, which is considered to be a soil type in China, is defined as “a multi-functional natural complex composed of herbaceous and wooden forage plants together with the soil supporting them.” Grasslands are classified into several types, including natural grasslands with total coverage over 5%, campos cerrados whose crown density is under 0.3 and primarily used for grazing, shrub herbosas with crown density under 0.4, secondary grasslands after fallowed over 5 years, artificial ranges, and various greenbelts dominated by perennial herbaceous plants. In general, grasslands are divided into two categories-natural grasslands and artificial grasslands. The former, which is also called steppe (Li, 1979), referred to plant communities dominantly constituent of microthermic and xerophilous perennial herbage, on some occasions of small xeric half-shrubs. Steppe is the principal component of grassland in China. This chapter’s discussion is also confined to steppes.
