围封与放牧管理对高寒草甸植物功能性状和功能多样性的影响

植物功能性状能够响应生存环境的变化并直接决定着生态系统功能。为了揭示围封与放牧管理对物种共存和驱动群落构建的影响机理,该研究以青藏高原东缘高寒草甸为对象,分析了围封与放牧处理对植物功能性状和功能多样性的影响。结果显示:(1)在群落水平,放牧显著降低了比叶面积和植物高度;在物种水平,放牧群落中多数杂类草比叶面积减小,而莎草类和禾草类的比叶面积在处理间无显著差异。(2)叶干物质含量与比叶面积在围封和放牧处理中均呈显著负相关关系,在放牧处理中,叶干物质含量与植物高度呈显著的二次函数关系,即随着叶干物质含量的增大,植物高度先减小后增大;在同等比叶面积的情况下,与围封相比,放牧降低了叶干物质含量;在相同叶干物质含量的情况下,与围封相比,放牧降低了植物高度。(3)放牧在总体上降低了种间性状的平均差异,植物性状表现出趋同响应,具体表现为放牧减小了叶干物质含量和植物高度的种间差异;与围封相比,放牧显著提高了功能均匀度,减小了功能分离度。研究表明,不同植物种对放牧的响应模式存在差异,放牧降低了种间对光资源的竞争,可能增加了对土壤养分的竞争,放牧驱动群落构建的过程中,土壤养分是非常重要的作用因子,说明放牧影响物种共存依赖于对多种资源的竞争。

Effect of Fencing and Grazing Management on the Plant Functional Traits and Functional Diversity in an Alpine Meadow on the Tibetan Plateau

Plant functional traits could respond to the variation of habitat and directly influenced ecosystem function. In order to explore the underlying mechanisms of how fencing and grazing affected species coexistence and community assembly, we analyzed effects of fencing and grazing on plant functional traits and functional diversity in an alpine meadow on the Tibetan Plateau. The results showed that: (1) grazing significantly decreased specific leaf area and plant height at the community level. Under grazing, specific leaf area tended to decrease for forbs at the species level, however, there was no significant difference for sedges and grasses compared with fencing. (2) Leaf dry matter content was significantly negative correlated with specific leaf area. Leaf dry matter content and plant height was significantly quadratic functional correlation in the grazing treatment. Plant height decreased first and then increased with the increase of leaf dry matter content in the grazing treatment. Leaf dry matter content were lesser for grazing than that for fencing in the case of equal specific leaf area. Plant height was lesser for grazing than that for fencing in the case of equal leaf dry matter content. (3) Grazing decreased the average dissimilarity of traits among species, caused traits convergence on the whole. Dissimilarity of leaf dry matter content and plant height among species was significantly lesser for grazing than that for fencing. Functional evenness significantly increased, and functional divergence significantly decreased after grazing. The results indicated that different species had different response modes to grazing and fencing treatments. Grazing decreased competition for light among neighboring while could increase competition for soil nutrient. Soil nutrient was a key factor in the process of community assembly driven by grazing. Therefore, the influence of grazing on species coexistence attributed to competition for multiple resources.