Explaining patterns of species dominance in the shrub steppe systems of the Junggar Basin (China) and Great Basin (USA)
The objective of this study was to investigate how climate, land use and community structure may explain these patterns of species dominance. We found that differences in summer precipitation and winter minimum temperature, land use intensity, and shrub size may all contribute to the dominance of annual species in the Great Basin, particularly cheatgrass. In particular, previous work indicates that summer precipitation and winter temperature drive the distribution of cheatgrass in the Great Basin. As a result, sites with wet summers and cold springs, similar to the Chinese sites, would not be expected to be dominated by cheatgrass. A history of more intense grazing of the Chinese sites, as described in the literature, also is likely to decrease fire frequency, and decreases litter and shrub dominance, all of which have been demonstrated to be important in cheatgrass establishment and ultimate dominance. Further research is necessary to determine if other annuals that follow the same pattern of scarcity in the Junggar Basin and dominance in the Great Basin are responding to the same influences.