Tree diversity and arbuscular mycorrhizal trees increase soil carbon sequestration and stability in 1-m soils as regulated by microbial CAZymes-coworking in high-latitude Northern Hemisphere forests.

• Tree richness and mycorrhizal-symbionts effects on SOC, GRSP-C, Rh, Q 10, Hs and GHGs were studied. • High tree richness induced 16–126.6% higher SOC, TG-C, Rh, and in situ N 2 O flux. • AM dominant plots had 34–39% higher SOC and Rh than the ectomycorrhizal plots. • Richness and AM's effects in 0–1 m soils were more evident than 0–20 cm soils. • Richness directly improved stability, while richness-AM-decreased-CAZymes favoured storage accrual. • Six types of CAZymes of GHs, PLs, CEs, GTs, AAs and CBMs cooperatively worked in the regulation. Biodiversity loss and tree alternations often occurred in high-latitude Northern Hemisphere forests owing to climatic changes and human disturbance, while their effects on soil carbon sequestration remain unclear. In this paper, tree richness and arbuscular mycorrhizal (AM)-tree dominance experiments were settled in an experimental forest, and soil organic carbon (SOC) and glomalin-related soil protein carbon (Total, TG-C and easily extracted, EEG-C), stability (heterotrophic respiration, Rh, temperature sensitivity, Q 10 and humidity sensitivity, Hs), in situ soil CO 2 , CH 4 , N 2 O fluxes, and CAZymes activities from the microbial metagenome technique were measured to identify their impacts and underlying mechanism. Both analysis of variance (ANOVA) and linear regression found tree richness and AM tree loss accompanied by soil carbon sequestration loss of total SOC storage, their mycorrhizal components (TG-C) and Rh. In 0–20 cm soils, high tree richness quadrats had 16–126.6 % higher SOC, TG-C, Rh, and in situ N 2 O flux, while AM-dominated stands had 34–39 % higher SOC and Rh than the EcM-dominated stands. In the 1 m soil profile, the effect size from tree richness and AM trees were more evident than the 0–20 cm soils. Compared with the richness gradient, much significant differences occurred between AM- and EcM-dominated stands. Structural equation modeling found that tree richness directly improved C stability, while the SOC accrual from the tree richness enrichment and AM-tree dominance were indirectly achieved by their decreasing in multiple CAZymes activities. Of CAZymes, glycoside hydrolases, polysaccharide lyases, carbohydrate esterases, glycosyl transferases, auxiliary activities, and carbohydrate-binding modules cooperated in their regulation of the soil C accrual. Our findings support carbon sequestration via biodiversity conservation and proper forest management related to tree mycorrhizal symbionts. [ABSTRACT FROM AUTHOR]