Canopy gaps disturbance enhances ecosystem multifunctionality by increasing species and phylogenetic diversity in Picea schrenkiana forests.

Canopy gaps, as a common type of natural disturbance in forest ecosystems, drive biodiversity changes via niche differentiation, thereby effecting ecosystem multifunctionality (EMF). However, which dimension of biodiversity (e.g. species, functional, and phylogenetic diversity) that more greater effects and explains EMF remains controversial. Here, we investigated the species, functional, and phylogenetic diversity across non-gaps (NG), small gaps (GS), medium gaps (GM), and large gaps (GL) in Picea schrenkiana forests after gap disturbance. Meanwhile, nine single ecosystem functions were used to quantify the EMF to assess the relationship between biodiversity and EMF. The results reveal that biodiversity and EMF increased significantly from GS to GL, but biodiversity more significant. Species richness (SR), Faith's phylogenetic diversity (PD), and canopy gap size (CGS) were the key factors effecting EMF, explained 32.41 %, 30.20 %, and 20.80 %, respectively. SR and PD showed a significant positive effect on EMF at low-medium thresholds. When CGS exceeded the 80 m threshold (GM level), SR and PD were exhibited a significant positive effect on EMF. Structural equation modelling explained 60 % of EMF variation, species and phylogenetic diversity effected EMF strength less than CGS, but were more significant. Moreover, soil physical properties shown significant negative effect on EMF. Our results clearly indicate that changes in SR and PD commencing from the GM level were key determinants and explanatory variables effecting EMF. This provides a crucial theoretical foundation for biodiversity conservation, ecosystem function realisation, and forest management in the subalpine Picea schrenkiana forests ecosystem after gap disturbance.