青藏东缘高寒草甸植物群落结构及功能群特征对长期季节放牧的响应

Responses of Plant Community Structure and Functional Group Characteristics to Long-term Seasonal Grazing in an Alpine Meadow on Eastern Qinghai-Tibet Plateau

为阐明高寒草甸植物群落对长期季节放牧的响应机制,本试验选取有10年以上冷、暖季放牧历史的湿生、中生、旱生高寒草甸进行探究。结果显示暖季放牧(6月至10月)下,湿生草甸香农指数与物种丰富度均显著小于冷季放牧(11月至翌年5月)(P<0.05),而旱生草甸多样性指数显著大于冷季放牧(P<0.05);冷季放牧地上生物量显著高于暖季放牧(P<0.05),其中暖季放牧下莎草科地上生物量所占比例最高。湿生草甸暖季牧场与旱生草甸冷季牧场莎草科重要值最高,其余牧场均为双子叶杂草重要值最高(P<0.05);经ANOSIM检验,季节性放牧下群落结构均有显著差异(P<0.01),湿生、旱生草甸群落结构差异较大,而中生草甸群落结构差异较小。本研究表明长期季节性放牧会影响植物群落结构特征,研究可为不同生境草甸的放牧制度和可持续发展提供理论基础。

To explain the mechanism of community structure,diversity,and functional group characteristics of plants responding to seasonal grazing in alpine meadows on Qinghai-Tibet Plateau,in this paper,three types of habitat meadow with a seasonal grazing history for more than 10 years were selected on the eastern Qinghai-Tibet Plateau:Hydric meadow,Mesophytic meadow,Xerophytic meadow.The results showed that the Shannon’s Wiener index and species richness under warm season grazing(June to October)were significantly lower than that under cold season grazing(November to April of the following year)in the hydric meadow(P<0.05).However,the plant diversity index under warm season grazing was significantly higher than that of cold season grazing in xerophytic meadows(P<0.05).The aboveground biomass of plant communities under warm season grazing was significantly lower than that under cold season grazing and the proportion of Sedge was highest in all three types of meadows under warm season grazing.The importance values of Sedge were the highest in warm season grazing of hydric meadow and cold season grazing of xerophytic meadow,and the important values of forb were the highest in other pastures under seasonal grazing(P<0.05).By principal component analysis and the similarity analysis(ANOSIM)test,the ANOSIM test R values were 0.877 and 0.761 under cold and warm season grazing,respectively,showing extremely significant differences(P<0.01).Seasonal grazing had great effects on the hydric and xerophytic meadows,but little effect on the mesophytic meadow.Therefore,long-term seasonal grazing will affect the characteristics of plant community structure,alpine meadows of different habitat types had different changes in response to long-term seasonal grazing.The findings could provide a theoretical basis to set up a reasonable seasonal grazing system as well as sustainable development of alpine meadows along the Qinghai-Tibet Plateau.