Soil properties and plant diversity co-regulate ecosystem multifunctionality of subalpine primary dark coniferous forest on the eastern Qinghai-Tibetan Plateau.

Aims: Plants and soils are key factors in maintaining ecosystem multifunctionality (EMF). Yet, it remains unclear how climate factors regulate the EMF through soil properties and plant diversity of different plant functional groups in primary dark coniferous forests of subalpine regions. Methods: Nine functional indicators related to carbon, nitrogen, phosphorus cycling and plant productivity, four leaf functional traits, mean annual precipitation (MAP) and mean annual temperature (MAT) were collected from 50 primary dark coniferous forests in ten sites on the eastern Qinghai-Tibetan Plateau. The EMF was calculated using two approaches. The averaging approach involves converting and averaging the functional indicators, and the multiple threshold approach quantifies the number of functions across different thresholds. Results: MAP promoted EMF. Soil water content and shrub species richness had a significant positive effect on EMF, whereas herb species richness had a negative effect. Functional diversity and specific leaf area of tree species rather than richness had a significant positive effect on EMF, indicating the increase in functional traits was beneficial to EMF. Climatic factors could directly or indirectly affect EMF through species richness, functional diversity, and soil abiotic factors. Conclusions: The effects of species richness on EMF varied among different plant functional groups, possibly related to different mechanisms, and highlighted the role of functional diversity in maintaining EMF. Spatial variation in climate could modify soil properties and plant diversity, further affecting EMF in primary dark coniferous forests. Hence, these findings should be considered in future predictions of how a changing climate could affect EMF. [ABSTRACT FROM AUTHOR]