Degradation significantly decreased the ecosystem multifunctionality of three alpine grasslands: evidences from a large-scale survey on the Qinghai-Tibetan Plateau

Owing to the joint effects of ecosystem fragility, anthropogenic disturbance and climate change, alpine grasslands (alpine meadow, alpine steppe and alpine desert) have experienced serious degradation during the past several decades. Grasslands degradation has severely affected the delivery of ecosystem multifunctionality (EMF) and services, and then threatens the livelihood of local herdsmen and ecological security of China. However, we still lack comprehensive insights about the effects of degradation and climatic factors on EMF of alpine grasslands, especially for alpine desert ecosystem. Therefore, we applied a large-scale field investigation to answer this question. Our results suggested grassland degradation significantly decreased the belowground ecosystem multifunctionality (BEMF) and EMF of alpine grasslands and aboveground ecosystem multifunctionality (AEMF) of alpine meadow, while did not reduce the AEMF of alpine steppe and desert. Except for the insignificant difference between degraded steppe and degraded desert in AEMF, the alpine meadow showed the highest AEMF, BEMF and EMF, alpine steppe ranked the second and alpine desert was the lowest. AEMF, BEMF and EMF of health alpine grasslands were strongly affected by mean annual precipitation (MAP) (19%–51%) and mean annual temperature (MAT) (9%–36%), while those of degraded meadow and degraded desert were not impacted by precipitation and temperature. AEMF and BEMF showed a synergistic relationship in healthy alpine grasslands (12%–28%), but not in degraded grasslands. Our findings emphasized the urgency of implementing the feasible ecological restoration project to mitigate the negative influences of grassland degradation on EMF of alpine ecosystems.