滇西北退化高寒草甸植物群落结构对刈割的响应

为探究滇西北不同退化级别高寒草甸植物群落结构对外界干扰的响应敏感性，以香格里拉市的典型高寒草甸为研究对象，于2018-2020年在三个退化梯度上（严重退化，S1；中度退化，S2；轻度退化，S3）开展控制刈割实验，进而分析草甸植物物种丰富度、群落组成相似性、群落复杂度和关键种的变化规律。结果表明：（1）刈割后，S1的物种丰富度显著增加（P<0.05），S2和S3的物种丰富度未发生显著变化（P>0.05）；（2）相较于S2和S3，S1梯度的植物群落组成变化最大；（3） S1、S2和S3的植物群落复杂度在刈割后均呈先下降后增加的趋势，但S1的植物群落复杂度变化幅度高于S2和S3；（4）刈割导致各退化草甸植物群落的关键种发生了变化，2018、2019和2020年S1梯度的关键种在豆科（Leguminsae）和蔷薇科（Rosaceae）之间变化，S2梯度的关键种在禾本科（Gramineae）和菊科（Compositae）之间变化，S3梯度的关键种在蔷薇科（Rosaceae）、菊科（Compositae）和禾本科（Gramineae）之间转变。研究表明，滇西北高寒草甸植物物种丰富度、群落组成和群落复杂度对外界干扰响应的敏感性可能随退化加剧而上升，但群落关键种的响应过程较复杂。

Responses of plant community structure to mowing in the degraded alpine meadows, Northwestern Yunnan Province

To explore the sensibility of the response of plant community structure to external disturbances under different degradation conditions in the Northwestern Yunnan Province (NWYP), we conducted a mowing experiment at three degradation gradients (i.e., S1:severe degradation; S2:moderate degradation; S3:slight degradation) in an alpine meadow in Shangri-La from 2018 to 2020. The effects of mowing on community structure indicators, including species richness, community similarity, community complexity and keystone species were analyzed. The results showed that (1) after mowing, the species richness of S1 increased significantly (P<0.05), while the species richness of S2 and S3 did not change significantly (P>0.05). (2) Mowing caused a greater change in community similarity in S1 than in S2 and S3. (3) The network connectivity of plant community decreased firstly and then increased after mowing in all degradation levels. Moreover, the change range of community complexity in S1 was higher than in S2 and S3. (4) The keystone species of plant communities changed in 2018, 2019 and 2020. In S1, the keystone species varied between Leguminsae and Rosaceae. In S2, the keystone species varied between Gramineae and Compositae. In S3, the keystone species varied among Rosaceae, Compositae and Gramineae. The study suggests that the sensitivity of the response of species richness, community composition and complexity of plant community to external disturbance might increase with meadow degradation levels, while the shifting of the keystone species would be complex in NWYP.