Divergent successions to shrubs- and forbs-dominated meadows decrease ecosystem multifunctionality of hillside alpine meadow

Global climate change and overgrazing pressure both affects the community succession, and multifunctionality of grassland ecosystems. Alpine meadows cover 1/3 of the Qinghai-Tibetan Plateau of China's climate sensitive area and major pastures, which is the main grassland ecosystem. However, the responses of ecosystem multifunctionality during climate change and overgrazing induced divergent community succession to shrubs- and forbs-dominated community remains poorly understood in alpine meadow ecosystem. Here, we examined five ecological functions, including above- and below-ground productivity, soil water holding capacity, soil organic carbon stocks and soil erosion resistance capacity of the native Kobresia-dominated alpine meadow ecosystem during the divergent succession to shrubs- and forbs-dominated meadow located on the Qinghai-Tibetan Plateau, and identified the key factors contributing to the changes of ecosystem multifunctionality during the divergent succession. Results showed that the divergent succession to shrubs- and forbs-dominated meadow both significantly reduced community species diversity and richness, changed community structure, especially the decreasing of the Sedges and Leguminous functional groups. Meanwhile, the ecological functions including below-ground productivity, soil water holding capacity, and soil organic carbon stocks are greatly decreased along shrubs and forbs encroachment in hillside alpine meadows. Taken together, our results demonstrate that climate warming and overgrazing induced divergent successions to the shrubs-encroached and the forbs-encroached communities both decreased the ecosystem multifunctionality of hillside alpine meadows. The ecosystem multifunctionality of hillside alpine meadow ecosystem might therefore be decreased continuously under ongoing and future climate warming and overgrazing by herbivores.