Divergent responses of ecological functions to long-term herbivore exclusion in the Tibetan mountainous grasslands

Herbivore exclusion is a widespread practice used to restore and manage degraded grasslands on the Tibetan Plateau. However, experimental evidence for the long-term impacts of herbivore exclusion on ecosystem structure and functioning of mountainous grasslands is still largely lacking. Here, we examined long-term herbivore exclusion impacts on ecological functions across four typical grassland types (alpine screes, alpine meadow, alpine steppe, and swamp meadow) along an elevation gradient on the southern slope of Nyaiqentanglha Mountain. The results showed that long-term herbivore exclusion had divergent influences on ecosystem functioning of mountainous grasslands, with the EMF tended to decrease in swamp meadow and alpine steppe but increase in alpine meadow and alpine screes. In addition, herbivore exclusion tended to decrease the aboveground ecosystem multifunctionality (AEMF) but had a trend to increase the belowground ecosystem multifunctionality (BEMF). Path analysis of the structural equation model showed that herbivore exclusion regulated EMF and BEMF mainly through altering plant productivity and soil nutrients while influenced the AEMF primary by affecting plant diversity. These findings revealed that the impacts of long-term herbivore exclusion on multiple ecological functions greatly depended on plant diversity, productivity, and soil nutrients, with the mountainous grasslands mostly experiencing decrease trends on ecosystem multifunctionality. The findings also highlighted the fundamental importance of developing proper grazing management practice for protecting ecosystem multifunctionality in the widespread mountainous grasslands on the Tibetan Plateau.