青藏高原亚高寒草甸封育区鼢鼠扰动对植物群落物种多样性和生产力的影响

Effects of zokor disturbance on species diversity and community productivity of Subalpine meadows in Qinghai-Tibet Plateau

从群落和功能群两个水平出发,通过对比分析不同恢复年限的鼢鼠土丘植物群落的物种多样性和生产力特征差异,了解小尺度斑块扰动对草地植物群落组成结构及功能特征的影响,探讨相应尺度上植物群落的物种多样性和群落生产力的关系.结果表明:亚高寒草甸围栏封育区内鼢鼠土丘植被的演替过程中,群落水平的物种丰富度和多样性指数均呈对数增长模式,群落内物种均匀性指数亦逐渐增加,群落生产力线性显著增加;功能群水平上,短命类杂草的物种丰富度的变化趋势不显著,但其在群落中的相对盖度逐渐降低,地上生物量先增加后降低;多年生杂类草的物种丰富度、相对盖度和地上生物量均呈极显著的增加模式;豆科植物的物种丰富度和地上生物量均呈显著增加模式,而其相对盖度逐渐增加,但拟合结果不显著;禾本科植物的物种丰富度、相对盖度和地上生物量均呈显著增加模式;群落物种多样性与生产力均呈极显著正相关关系;功能群水平上,4种类群植物的物种丰富度与群落生产力呈显著正相关关系,多年生杂类草和豆科植物的香浓威纳指数与其相应类群生产力呈显著正相关关系,而短命杂类草和禾本科植物的香浓威纳指数却与其相应类群的生产力呈正相关关系但不显著.围封条件下,随鼢鼠土丘植物群落的演替,群落物种丰富度的增加对生产力的促进作用,可能是由不同功能群间生态位的差异、物种间对资源的互补性利用能力和扩散限制引起的.

Based on the two levels of community and functional groups, differences of species diversity and community production of vegetation on zokor mounds were compared along the successional stages,aiming at understanding the effects of a small scale disturbance on species composition and functional traits of plant communities, and the relationship between species diversity and community production during the restoration process was discussed. The results showed that, during the succession of plant community on zokor mounds in the enclosure site of subalpine meadows and at the community level, both the species richness and diversity index showed a logarithmic and increasing pattern, species evenness were also gradually increased and community production presented a significant linear increasing trend. At the functional group level, the trend on species richness of ephemeral forbs was not significant： it declined in the relative coverage, and its aboveground biomass first increased and then declined. All of the three indexes（species richness, the relative coverage and aboveground biomass） of perennial forbs exhibited a remarked significant increasing trend. Species richness and aboveground biomass of leguminous plants were of a significant increasing pattern, the relative coverage underwent an increasing trend but very insignificant; all of the three indexes（species richness, the relative coverage and aboveground biomass）of gramineous plants were of a significant increasing pattern. At the community level, species richness was remarkable and positively related with community productivity while at the functional group level,all of the four functional groups（ephemeral forbs, perennial forbs, leguminous and gramineous plants）exhibited a positive and remarkable correlation with community production. The Shannon-Wiener index of perennial forbs and leguminous plants was also significantly correlated with the referenced production,but the results of Shannon-Wiener index of ephemeral forbs and gramineous plants had no significant correlation with the referenced production. The above results indicated that, under the enclosure background, the increasing species richness could help improve community production, which may result from niche differences in functional groups, and from the complementary utilization ability of resources for different species and dispersal limitation.