The Impacts Of The Alpine Wetland And Grassland Degradation And Restoration On Ecological Networks And Ecosystem Functioning

Climate change and anthropogenic disturbances have significant impacts on ecosystems worldwide.On the Tibetan Plateau,climate warming-induced desiccation has transformed many swampy meadows into dry alpine meadows.In some areas,high-intensity grazing has further transformed alpine meadows into species-poor degraded meadows.Evaluating the consequences of these meadow transformations on above-and belowground community structure,ecological network and ecosystem functioning is important to predict the impact on biodiversity and develop ecological restoration strategies.There is an increasing demand to identifying suitable restoration management strategies for specific habitat and disturbance types to restore interactions between organisms of degraded habitats,such as pollination,and the associated ecosystem functions.However,we have little knowledge about the impacts of human-induced Tibetan meadow transformations on multiple layers of the ecosystem,especially on the inter-specific interactions and ecosystem multifunctionality.Moreover,the effects of widely used restoration method in this region on the inter-specific interactions and ecosystem functioning are seldom examined.Here,we assessed the responses of ecological networks of soil microbial communities and plant-pollinator communities to Tibetan meadow transformations and investigated the impacts of these changes on ecosystem multifunctionality based on natural experiment across replicated sites in the eastern Tibetan Plateau.We also investigated the effect of protecting vegetation by fencing during the growing season,which is a widely applied restoration strategy in this region,on plant-pollinator communities and plant reproduction in the eastern Tibetan Plateau,and how such restoration effects vary along the age of restoration.We found:1.As a result of swampy meadow desiccation,the composition of plant community and soil microbial communities changed significantly,species richness and ecological network complexity at multiple trophic levels increased,pollination networks became more robust while soil microbial networks became more vulnerable to species loss,which suggest that environmental changes impact above-and belowground ecological networks by different mechanisms.Pollination function appeared to benefit from the increased diversity in resources and the formation of dry soil,but important belowground functions of carbon storage and soil fertility decreased.Thus,there are trade-offs between ecosystem functions during swampy meadow desiccation.Overall,greater diversity and network complexity were associated with greater ecosystem multifunctionality in alpine meadows.2.When alpine meadows degrade further because of extensive grazing pressure,aboveground diversity and network complexity declined.Soil microbial richness and composition remain unchanged but the associations among soil microbes homogenized,which indicates the associations among soil microbes are more sensitive to environmental changes than the soil microbes per se.At the same time,multiple ecosystem functions decreased,which ultimately decreased the ecosystem multifunctionality.3.Restoring degraded meadows by fencing during growing had benefits on pollination network and functions.Compared to meadows grazed across all year,meadows ungrazed during growing season produced more flowers(20.97%)and attracted more pollinator visits(23.79%).Furthermore,plants in ungrazed meadows were more robust to secondary species extinction than those in grazed meadows.The observed changes in the networks corresponded with higher seed set of plants that rely on pollinators for reproduction.Besides,our result showed the hump-shaped response of the restoration effect of grazing exclusion to the age of restoration,the highest restoration effect was observed around the eighth year after grazing exclusion.Overall,our study investigated the multilayered response of above-and belowground multitrophic biotic communities and multiple ecosystem functions to human-mediated Tibetan meadow transformations,and evaluated the effects of widely used ecological restoration management(grazing exclusion)on ecological network and functions and its annual dynamics.Our study highlights that understanding the detailed effects of meadow transformations on above-and belowground diversity and ecological networks,as well as ecosystem functions are needed to improve the conservation and restoration of biodiversity and ecosystem functioning in the Tibetan Plateau.In addition,we also demonstrate that protection from grazing in growing seasons is a viable restoration approach for degraded meadows,but the age of grazing exclusion should be moderate.Our study provides new insights to the future conservation and restoration management.