Impacts of small herbivore disturbance on grassland ecosystem multifunctionality on the Qinghai-Tibetan Plateau

As a critical global ecosystem, grasslands rely on complex aboveground-belowground interactions that underpin multifunctionality, yet their mechanisms remain poorly understood. Our investigation employed the plateau pika (Ochotona curzoniae), a small herbivore widely distributed throughout the Qinghai-Tibetan Plateau, as a model organism to examine the consequences of disturbance on plant diversity, soil properties, microbial diversity, and multifunctionality of grassland ecosystems. We found that high pika burrow density significantly reduced plant diversity (Shannon-Wiener and Chao1 indices) and aboveground biomass. It also increased soil pH and reduced ammonium nitrogen content. The soil microbial diversity, encompassing both bacteria and fungi, was markedly decreased in areas characterized by a high concentration of burrows. Microbial interaction networks demonstrated greater complexity in areas with high burrow densities, as revealed by the network analysis. Conversely, in regions characterized by low burrow density, a significant negative correlation was observed between the intricacy of soil bacterial networks and the multifunctionality of grassland ecosystems. Structural equation modelling showed that pika disturbance indirectly affected multifunctionality via changes in plant biomass and soil properties—notably, nitrate nitrogen explained 40% of multifunctionality variation under high disturbance. This investigation advances our understanding of complex aboveground-belowground linkages in grassland ecosystems, revealing novel mechanisms through which biodiversity governs ecosystem multifunctionality. Our findings underscore the critical role of small herbivores in shaping grassland ecosystem functions and emphasize the importance of maintaining balanced disturbance regimes to sustain ecosystem multifunctionality. This has immediate implications for global conservation policies on the Qinghai-Tibetan Plateau and analogous ecosystems.