摘要:高山草甸作为一种发育在高山林线以上位置的植被类型，高大的海拔促使其对气候变暖响应敏感而迅速，其群落结构在气候变暖影响下发生着显著变化。然而，现在的研究大都集中在诸如极地、青藏高原等高纬度、高海拔地区，对于中低纬度、低海拔地区分布的亚高山草甸研究就显得不足。因此，为了揭示中纬度、低海拔地区亚高山草甸群落结构在气候变暖背景下的动态变化规律，以山西云顶山亚高山草甸为研究对象，设置小幅度增温（OTC₁）和大幅度增温（OTC₂）两种模拟增温实验样地，调查草甸空气-土壤水热因子及植被群落结构特征，探究增温对亚高山草甸水热因子及群落结构的影响。结果表明：（1）在OTC₁和OTC₂处理下，草甸空气呈现暖干化，其中空气温度分别增加3.57℃和和5.04℃（P<0.05），空气湿度分别减小7.36%和5.23%（P<0.05）；草甸土壤趋向暖湿化，其中土壤温度分别减小0.05℃和增加0.26℃（P<0.05），土壤水分分别减小0.2%和增加0.62%（P>0.05）。（2）增温对草甸物种多样性产生一定负面影响，但Richness指数、Simpson指数、Shannon指数在不同处理间的差异均不显著（P>0.05），表明物种多样性对增温响应不敏感。（3）增温促进草甸群落中禾草类植物生长，抑制杂草类植物生长，且随增温幅度变大，群落中不同植物功能型由杂草类向禾草类转化。（4）RDA排序和相关分析表明，空气、浅层土壤温度促进禾草生长，抑制杂草生长；深层土壤温度抑制莎草生长；浅层土壤水分促进禾草生长。因此，增温改变了云顶山亚高山草甸的水热因子状况，导致草甸群落结构发生改变，使之向禾草类植物进行演替。



Abstract:Climate warming has become more pronounced in contemporary times due to the effects of human activities. Alpine meadow is one of the typical vegetation types at high elevations above the treeline on large mountains. Owing to their high-altitude environment, these meadows are sensitive and respond swiftly to climate warming. The community structures of alpine meadows are also significantly affected by climate warming. Most current research, however, has been carried out in high-latitude and high-altitude areas, such as the polar region and the Qinghai-Tibetan Plateau. With regard to subalpine meadows distributed in medium-low-latitude and low-altitude areas, the related studies and conclusions are insufficient. Aiming to reveal the variation of community structure in subalpine meadows in medium-latitude and low-altitude areas under the climate warming, we selected Yunding Mountain, which is the highest peak in the western Shanxi Province, as the study area. Yunding Mountain contains typical subalpine meadows, one of which was selected as the study area in this research. Here, we designed experimental warming plots with 2 amplitudes: small and large. The warming devices were open-top chambers (OTCs) with a small-warming amplitude (OTC₁) and a large-warming amplitude (OTC₂). The OTC heights were 40 cm for OTC₁ and 80 cm for OTC₂. The warming experiment lasted one year. The warming plots were completed in August 2016 and their hydrothermic factors and community structures in the subalpine meadow were measured in July 2017. The results showed that: (1) the air in the meadow was warm and dry in both the small- and large-warming treatments, with corresponding air temperature increases of 3.57℃ and 5.04℃ (P<0.05), and corresponding air humidity decreases of 7.36% and 5.23% (P<0.05). The soil of the meadow trended toward warm and wet, with soil temperatures decreasing by 0.05℃ in OTC₁ and increasing by 0.26℃ in OTC₂ (P<0.05), and soil moisture decreasing by 0.2% and increasing by 0.62% (P>0.05), respectively. (2) Warming had certain negative effects on species diversity in the meadow. However, differences between the treatments were not significant for the species richness index, Simpson's index, and the Shannon's index (P>0.05). This indicates that species diversity of the subalpine meadow is not sensitive to warming. (3) Warming accelerated the growth of grasses and inhibited the growth of forbs in the meadow community, with the different plant functional types transforming from forb to grass with increasing warming amplitude. (4) Redundancy analysis (RDA) ordination and correlation analysis indicated that air and shallow soil temperatures promoted the growth of grass and suppressed the growth of forb; deep soil temperature restrained the growth of sedge; and shallow soil moisture facilitated the growth of grass. In conclusion, warming changed the status of the hydrothermic factors in the subalpine meadow of Yunding Mountain, resulting in an alteration of its community structure, inducing a transformation toward grass.





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