Thresholds for the relationships between soil trace elements and ecosystem multifunctionality in degraded alpine meadows

Trace elements in soil are known to affect ecosystem functions, such as soil microbial structure, function, and grassland productivity. However, it is largely unknown whether soil trace elements cause abrupt or gradual changes in ecosystem multifunctionality (EMF) in degraded alpine ecosystems and how they depend on environmental drivers. In this study, we investigated the vegetation and soil conditions in 172 sample squares in an alpine meadow area on the Tibetan Plateau, China. This study aimed to analyse the change characteristics in alpine meadow EMF and soil trace element contents at different degradation stages. Furthermore, we evaluated the soil trace element contributions to alpine meadow EMF. This study revealed that EMF decreased with increasing degradation, whereas total soil micronutrient content exhibited the opposite trend. A threshold was identified for regulating EMF using micronutrients during alpine meadow degradation. Soil micronutrients enhanced EMF during the initial stages of alpine meadow degradation. However, as degradation progressed, elevated soil micronutrient levels impeded EMF. In addition, climate can modulate soil trace elements through plant diversity and soil physicochemical properties, thereby influencing the role of soil trace elements in driving EMF. Soil physicochemical properties contributed the most to EMF, whereas soil trace elements, rather than plant diversity, significantly influenced EMF. Overall, soil trace elements in the degraded meadows had a significantly negative impact on EMF.