若尔盖高寒草甸不同功能群植物数量特征对退化演替的响应

Responses of plant functional groups to the de-gradational succession of alpine meadow in Zoigê County

为了查明若尔盖高寒草甸退化过程中植物群落各功能群数量特征的变化趋势,2013年8月利用样方法对若尔盖县境内的沼泽草甸、草原草甸、中度退化草甸和重度退化草甸的植物群落和土壤环境进行了调查.结果为:草地退化过程中,禾本科植物密度、高度和重要值均无显著变化,仅盖度呈显著波动性变化;莎草科植物密度、高度、盖度在中度退化前均无显著变化,重度退化阶段显著降低,重要值呈持续显著下降趋势;豆科植物高度和盖度以中度退化阶段最高,但密度和重要值以草原草甸最高,重度退化阶段最低;蓼科植物密度、高度、盖度和重要值从沼泽草甸到中度退化阶段均显著增加,重度退化阶段消失;杂类草植物密度和盖度在退化过程中呈波动变化,高度和重要值呈波动性增加趋势.结果表明:高寒草甸不同退化阶段功能群植物的生长规律不尽相同,但严重退化可显著影响莎草科、豆科、蓼科和禾本科的生长.回归分析表明土壤氮、磷、钾含量是莎草科、豆科和蓼科的主要限制因子,这意味着向退化高寒草甸中同时施加氮、磷、钾三种肥料将可以促进莎草科、豆科和蓼科植物的生长,有利于高寒草甸生态恢复.

The swampy meadow, grassland meadow, moderately degraded meadow and seriously degraded meadow, which represent four degradation phases of alpine meadow, were selected in the Zoige County, and plant community （classified into five functional groups： Grasses, Sedges, Leguminosae, Polygonaceae and Forbs） and soil environment were investigated using plots method in August 2013 to reveal the dynamics of plant function groups with the degradation of alpine meadow. Results showed that the density, height and important value of grasses did not change significantly with the degradation of alpine meadow, while a significant fluctuation was found in its coverage. For sedges, the density, height and coverage changed with no significance before the moderate degraded meadow phase, but significantly decreased in the serious degraded meadow, while the important value decreased significantly among the degradation phases. For the Leguminosae, the maximum values of height and coverage were found in the moderately degraded meadow, but that of the density and important value was in the grassland meadow, and all of the indexes were the lowest in seriously degraded meadows. In terms of Polygonaceae, the density, height, coverage and important value were significantly increased from swampy meadow to moderately degraded meadow. However, Polygonaceae disappeared in seriously degraded meadows. Additionally, the density and coverage of Forbs fluctuated during the degradation process, and an increasing trend was observed in the height and important value. These results show that the plant functional groups have different responses to the degradation of alpine meadow, and the growth of sedges, Leguminosae, Polygonaceae and grasses is limited in seriously degraded meadows. In the meantime, the results of regression analysis show that the main limiting factors for the plant functional groups of sedges, Leguminosae and Polygonaceae are soil nitrogen, phosphorus and potassium contents, which indicated that adding nitrogen, phosphorus and potassium to the degraded alpine meadow can promote the growth of Sedges, Leguminosae and Polygonaceae, and thus contributing to the restoration of alpine meadow.