内蒙古不同草地类型隐子草种群对放牧强度的响应

Response of Cleistogenes to Grazing Intensity in Different Grasslands of Inner Mongolia

放牧胁迫使隐子草(Cleistogenes)种群成为退化草地的优势种,而继续加重放牧致使隐子草逐步衰退。由于在退化过程中隐子草作为退化指示种和重度退化的过渡种其种群格局将发生变化,故以内蒙古草甸草原、典型草原、荒漠草原为研究对象,设置轻度、中度、重度以及对照样地4个放牧强度,经过5年的连续野外试验和研究,对隐子草在不同放牧强度下的变化趋势进行分析,以期为草地管理提供理论基础。研究结果表明,(1)无论是草甸草原还是典型草原、荒漠草原,退化草地指示种隐子草都呈现明显的随放牧强度增加而先增加后减少的趋势,只是不同草地类型对于年度以及峰值出现的情况是有差异的。(2)草甸草原和典型草原都是以中度放牧强度显著最高,而荒漠草原只在降水相对较高的2008年以中度放牧最高,在降水较少的2006年、2007年则以轻度放牧显著最高。(3)不同草地类型双因素方差分析结果表明只在典型草原中,年度因素对无芒隐子草(Cleistogenes songorica)有显著影响。草地类型和放牧对隐子草有显著影响(P<0.01),且草地类型、放牧和年度的两两交互作用对隐子草的影响显著(P<0.01)。

Cleistogenes populations become dominant species under moderate grazing pressure, and began to decline with a heavier grazing in the degraded grassland. There is a special pattern thatCleistogenes are indicator species in degraded grasslands and a transient species in the severe degradation grasslands during the degradation process. In this research, we focused onCleistogenes populations changes under four grazing intensity (Light grazing, moderate grazing, heavy grazing and control) in meadow steppe, typical steppe and desert steppe in Inner Mongolia five years continuous experiment and tried to analysis the variation tendency of Cleistogenes with grazing intensity, to provide theoretical basis for the management of rangeland. The results showed that: (1) Cleistogenes had an increasing trend at first and then decreased in th three types of steppes with the increasing grazing intensity. But the peak points were different in different years and steppes. (2) The relative biomass ofCleistogenes squarrosas was the the highest under moderate grazing in meadow steppe and typical steppe in every experimental year, while the relative biomass ofCleistogenes songorica was the highest only in 2008 with more precipitation under moderate grazing, and in 2006 and 2007 with insufficient precipitation under light grazing in desert steppe. (3) By comparison of two-factor analysis of different steppe types, the years have significant effect onCleistogenes squarrosas in the typical steppe. The steppe types, grazing intensities and the interaction have strong effect onCleistogenes. And the effects of the interaction between years and steppe types, the interaction between years and grazing intensities onCleistogenes were significant.