期刊
RANGELAND ECOLOGY & MANAGEMENT
卷 62, 期 4, 页码 321-327出版社
SOC RANGE MANAGEMENT
DOI: 10.2111/08-179.1
关键词
acetylene reduction assay; nitrogen fixation; nitrogen input; soil stability
Biological soil crusts (BSCs) are important in many arid arid semiarid ecosystems for their abilities to fix atmospheric nitrogen (N) and stabilize surface soil. Grazing disturbance has a profound influence on abundance, species composition, arid ecological functioning of BSCs. To elucidate the effects of grazing on BSCs in Inner Mongolia grasslands, all investigation was conducted in a typical steppe that had previously been subjected to long-term grazing with six grazing densities (control: 0 sheep.ha(-1), very light: 4 sheep.ha(-1), light: 8 sheep.ha(-1), medium: 12 sheep.ha(-1), heavy: 16 sheep.ha(-1), and very heavy: 20 sheep.ha(-1)). Cover, species composition, potential N-fixing activity, arid potential N input of BSC indicate that long-term grazing significantly reduced the importance of BSC in N input and soil stabilization. Such reductions were highly related to grazing density. Very light grazing had no significant effect on the role of BSC in soil stabilization, but resulted ill a 13.3% reduction in BSC N input potential. Heavy arid very heavy grazing led to a decrease of potential N input by one order of magnitude, and a decline of BSC function via a shift from high coverage of an attached group-dominated BSC community to a low coverage of a vagrant group-dominated community. Constraining grazing level to a very light density-and to a lesser extent, a light grazing density-is likely a preferred practice for conserving BSC arid the ecological services it provides ill N fixation and soil stabilization.
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