Tree species identity drives soil organic carbon storage more than species mixing in major two-species mixtures (pine, oak, beech) in Europe

Mixed forests are usually associated with higher aboveground carbon storage compared to the corresponding monocultures but information on impact of tree species mixing soil organic (SOC) is still limited. Yet, maximizing SOC crucial for ecosystem C sequestration and many other services. This study used a triplet approach (ie. two-species mixed stand respective pure stands at same site) assess identity in eight pine-oak, pine-beech five beech-oak triplets Europe. We sampled forest floor (FF) 0–40 cm mineral per 10 interval. For each type, we fitted basal area (BA) proportion one component (for identity) BA-based plot-level True Shannon Diversity index mixing) as explanatory variables stocks linear effects models, which included stone content plot BA covariates, site random intercept. Considering total depth (FF + cm), effect was only significant pine-oak explained more variability than across types. Species not any type depth. While consistently drove topsoil layers types, deeper except triplets. The results showed that stronger driver mixing. strongly related conifers vs broadleaves signature, drivers behind remained elusive. suggest targeted selection could better enhance European mere increase richness.