高原鼢鼠干扰对三江源区高寒草甸群落特征的影响

高原鼢鼠是三江源高寒草甸区域的主要啮齿动物之一.它啃食植物根系,挖掘大量通道,并将挖掘出的土壤堆积于地表,形成覆盖于植物地上部分的裸露土丘,对草地群落特征会产生不同程度的影响.本研究以高原鼢鼠土丘密度表示高原鼢鼠对草地的干扰程度,选取7个不同高原鼢鼠土丘密度的样地,同时选取没有遭受高原鼢鼠干扰的样地作为对照,获得各样地的物种信息及地上、地下生物量,探讨不同高原鼢鼠干扰强度对草地群落的物种组成、物种多样性及群落生产力的影响.结果表明: 随着高原鼢鼠土丘的增加,草地植物优势种群发生由以莎草科和禾本科植物为主向珠牙蓼、鹅绒委陵菜、西伯利亚蓼等杂类草植物为主的转变,群落盖度和高度显著降低;轻度或中度的高原鼢鼠干扰能够提高群落的物种多样性,而群落均匀度指数变化不显著;群落生产力不存在类似中度干扰假说的结果.随高原鼢鼠干扰活动的增强,群落地上、地下及总生物量显著降低,群落生产力大幅度降低.

Effects of Myospalax baileyi disturbance on plant community at alpine meadow in Three Rivers Headwater Region,China.

Plateau zokor (Myospalax baileyi) is one of the major rodent species at the alpine meadow in Three Rivers Headwater Region. They eat plant roots, excavate many tunnels and deposit soil on the surface, which result in many exposed mounds to cover the aboveground part of plants. Here, taking plateau zokor mound density in a plot as their disturbance degree, we selected seven plots with different plateau zokor mound densities and one control plot which was not disturbed by plateau zokor to explore the effects of M. baileyi disturbance on community composition, species diversity and productivity. The results showed that, with the increases of available mound density, the dominant species were changed from Cyperaceae and Gramineae species to forb species, including Poly-gonum viviparum, Potentilla anserine, and Polygonum sibiricum. The community coverage and height were significantly decreased. Light or intermediate disturbance by plateau zokor improved species diversity, whereas the evenness index showed no significant change. The changes of community productivity did not support the ‘intermediate disturbance hypothesis’. With the increases of plateau zokor disturbance, the aboveground biomass, belowground biomass, total biomass of community significantly decreased. Our findings revealed the effects of plateau zokor’s activity on plant community at alpine meadow and presented important information for the management and restoration of degraded grassland and the sustainable utilization of grassland in Three Rivers Headwater Region.