生长季放牧对高寒草甸传粉网络的影响

Abstract

植物-传粉者相互作用面临人类活动的威胁。在青藏高原地区，放牧是一项主要的人类活动干扰，过度放牧导致高寒草甸植被严重退化。然而在该区域放牧如何影响植物-传粉者相互作用网络还不得而知。在青藏高原东部的高寒草甸选取了两个研究样点，每个样点包括一块禁牧样地（生长季禁牧）和放牧样地（全年放牧）。在2016年至2018年每年的生长季（7月和8月）进行了连续3年观测，共构建16个传粉网络。结果发现，在研究区域的高寒草甸生态系统中，传粉者群落的物种组成以双翅目昆虫为主。放牧后双翅目、鳞翅目以及鞘翅目传粉者的种类数减少，但膜翅目传粉者的种类数未受到放牧的影响。放牧干扰显著降低了群落中植物、传粉者以及它们之间相互作用的多样性，但对传粉网络的嵌套性和特化程度（H₂'）没有显著影响，说明网络的稳定性和恢复力没有受到放牧的影响。探讨了放牧对传粉网络的影响，发现区域放牧强度过大，降低了传粉昆虫和传粉网络的多样性。未来需要进一步深入研究高寒草甸生态系统中放牧强度对传粉网络的影响模式，以期为合理的放牧制度模式提供理论依据。;Plant-pollinator interactions are threatened by human activities. In the Tibetan Plateau, grazing is one of the main anthropic disturbances, and overgrazing has led to degradation of alpine meadow. However, it is still unclear how grazing affects plant-pollinator interaction network of alpine meadows. Here we collected data from two locations in the eastern Tibetan Plateau to evaluate the effects of grazing on the pollination networks in alpine meadow. Each location comprised one ungrazed plot (fenced during growing season) and one grazed plot (grazed all year). We conducted surveys during growing seasons (July and August) in three consecutive years (2016-2018), and constructed 16 pollination networks in total. The plants-pollinators interactions were surveyed using timed observation method by cameras. We found that the pollinator communities of alpine meadow were dominated by Diptera species. The richness of Diptera, Lepidoptera and Coleoptera pollinators were decreased after grazing, while the richness of Hymenoptera pollinators was unaffected by grazing. Grazing reduced the diversity of plants, pollinators and their interactions. The generalism of plants was also decreased by grazing, but the nestedness and specialization (H₂') of networks were similar between treatments, indicated that the stability and resilience of pollination networks are unaffected by grazing. Furthermore, the network metrics were similar between different months, and grazing had similar impacts on pollination networks in July and August. Our study firstly investigated the effect of the grazing on the pollination networks of alpine meadows in the Tibetan Plateau. The results highlighted that the grazing intensity of study area is exceeded the optimum intensity as it decreased the diversity of pollinators and pollination networks. Further studies should focus on how pollination networks response to grazing intensity in alpine meadow to find a reasonable grazing regime.