Shrub encroachment in alpine meadow diminishes ecosystem multifunctionality, but shrub removal can facilitate recovery

In grasslands, shrub encroachment driven by climate change and anthropogenic disturbance alters various ecosystem functions. However, its effect on ecosystem multifunctionality, defined as the simultaneous performance of multiple ecosystem functions, is still poorly understood. Furthermore, the efficacy of removing shrubs to reverse the effects of shrub encroachment, a common management practice, remains debated. We aimed to disentangle the differential biotic (e.g., diversity of plant and soil) and abiotic responses within the herbaceous plant community to shrub encroachment and removal, and to explore how these changes drove shifts in ecosystem multifunctionality. This study was conducted in shrub-encroached (Potentilla fruticosa) alpine meadows on the Qinghai-Tibetan Plateau. We established a experiment with four treatments: natural grassland, shrub encroachment, artificial shrub installation, and shrub removal. We found that shrub encroachment reduced multifunctionality primarily by lowering soil water content. Shrub removal nearly reversed all negative alterations caused by encroachment, and specifically enhanced biotic attributes, like evenness, that in turn boosted multifunctionality. However, some of the effects of shrub removal remained incomplete relative to natural grassland. While artificial shrubs successfully reproduced the aboveground abiotic conditions (e.g., light and temperature) that actual shrubs do, they were less effective in evoking other environmental changes and did not affect multifunctionality. This study highlights that shrub encroachment induces substantial changes in both abiotic and biotic components, which thereby negatively affects multifunctionality and ecosystem services. Importantly, shrub removal proved to be an effective short-term solution with long-term potential for restoring these functions. Our findings provide key insights into the consequences of shrub encroachment, offering valuable guidance for ecosystem restoration and management aimed at mitigating its impacts in alpine meadows.