川西北不同退化程度高山草甸和亚高山草甸的植被特征

Comparison between the vegetation characteristics of alpine and subalpine meadow with different degradation degrees in North-west of Sichuan province

以川西北高原处于不同退化程度的高山草甸与亚高山草甸草地为研究对象,采用时空替换法和样方法对其退化演替过程中的植被特征进行了比较研究,以揭示两者退化过程中植被特征变化的相似性与相异性。结果表明,放牧干扰下的高山草甸草地物种丰富度变化,无明显退化-轻度退化-中度退化-重度退化呈高-低-高趋势,与亚高山草甸（低-高-低）相反,高山草甸退化演替上草地丰富度值变化范围为9.56~15.00种/m2（轻度退化最低约10种/m2）,亚高山草甸为11.80~25.08种/m2（轻度退化最高约25种/m2）。亚高山草甸物种多样性指数（Shannon-Wiener Index）与均匀度指数（Pielou Index）的变化均显著高于高山草甸。盖度和高度在高山草甸和亚高山草甸上均随放牧强度的增大而下降,但亚高山草甸重度退化草地盖度（88.50%）则增高。高山草甸有毒有害植物地上现存量占群落地上现存量的比例变化呈上升趋势,但未达极显著（P〉0.01）水平;亚高山草甸无明显退化比例较小,仅为0.37%,与轻度退化（16.86%）、中度退化（14.80%）、重度退化（8.33%）差异显著。

To explore the similarity and dissimilarity of vegetation characteristics during degraded process between alpine and subalpine meadow,the vegetation characteristics of these two types meadow with different degradation degrees in North-west of Sichuan province were investigated by using quadrates method.Results showed a high-low-high trends in terms of species richness as grassland degradation degrees changed from non-degraded to heavy degradation in alpine meadow,but a contrary tendency was observed in the subalpine meadow（low-high-low）.The variation of species richness in alpine ranged from 9.56 to 15.00 species/m2（the minimum was Light degradation 10.00 species/m2）,but the subalpine meadow ranged from 11.80 to 25.08 species/m2（the maximum was Light degradation 25 species/m2）.The variation of Shanon-Wiener index and Pielou index was relatively higher in subalpine meadows compared to alpine meadows.With the increase of grazing intensity,the vegetation coverage and height of alpine and subalpine meadows decreased except the heavy degradation of subalpine meadows.Percentage of unpalatable plants living aboveground biomass of alpine increased as meadow degraded but not statistic significant（P0.01）;by contrast,a significant decrease trends in the percentage of unpalatable plants living aboveground biomass was observed from light degradation（16.86%）,medium degradation（14.80%） to heavy degradation（8.33%） in subalpine meadow,in addition,in the non-degraded meadow of subalpine,it accounted for a less proportion,merely 0.37%.