Increasing soil organic carbon (SOC) in agroecosystems is a key objective for enhancing agricultural sustainability and mitigating climate change. Arbuscular mycorrhizal fungi (AMF) can increase yield and provide several other ecosystem services. Still, studies conducted in agricultural soils have shown that their effects on SOC can be either positive, neutral or negative. In this study, we conducted a quantitative review of the literature to evaluate the role of AMF in influencing SOC across various crop species and conditions. Through a systematic search of publications, we compiled a dataset comprising 62 trials from 19 studies including field and pot experiments that directly manipulated the mycorrhizal status of plants. We conducted a meta‐analysis to quantitatively evaluate the role of AMF on SOC across several crop species and conditions. We found an overall positive effect of AMF on SOC, with an average increase of 21.5%. However, this positive effect was statistically significant only in pot experiments whereas in field experiments, the effect was mainly modulated by texture and organic matter content. The effect of AMF on SOC did not vary with crop species' functional type, AMF inoculation sources (single or mixed AMF species) or other soil variables considered. Our results highlight the significant potential for AMF‐mediated mechanisms to promote SOC accumulation in agricultural soils, although this effect is context‐dependent. However, future research with different approaches and scales is needed to evaluate the impact of AMF on SOC dynamics in agricultural systems and elucidate the mechanisms behind their contribution to SOC accrual. Read the free Plain Language Summary for this article on the Journal blog.

Summary: Wood density is central for estimating vegetation carbon storage and a plant functional trait of great ecological and evolutionary importance. However, the global extent of wood density variation is unclear, especially at the intraspecific level. We assembled the most comprehensive wood density collection to date, including 109 626 records from 16 829 plant species across woody life forms and biomes (GWDD v.2, available here: doi: 10.5281/zenodo.16919509 ). Using the GWDD v.2, we explored the sources of wood density variation within individuals, within species and across environmental gradients. Intraspecific variation accounted for c . 15% of overall wood density variation (SD = 0.068 g cm ⁻³ ). Variance was 50% smaller in sapwood than heartwood, and 30% smaller in branchwood than trunkwood. Individuals in extreme environments (dry, hot and acidic soils) had higher wood density than conspecifics elsewhere (+0.02 g cm ⁻³ , c . 4% of the mean). Intraspecific environmental effects strongly tracked interspecific patterns ( r = 0.83) but were 70–80% smaller and varied considerably among taxa. Individual plant wood density was difficult to predict (root mean square error > 0.08 g cm ⁻³ ; single‐measurement R ² = 0.59). We recommend: (1) systematic sampling of multiple individuals and tissues for local applications; and (2) expanded taxonomic coverage combined with integrative models for robust estimates across ecological scales.