Host identity and fungal source pools shape mycorrhizal assembly under carbon removal interventions in large-scale afforestation

Host identity dominated mycorrhizal assembly in large-scale afforestation in Wales, and it was the strongest predictor of aboveground biomass, overshadowing inoculation and ERW effects.

• Why it matters: Soil inoculation and enhanced rock weathering may shift fungal communities, but it was unclear whether they alter root-colonising mycorrhizal fungi that support tree nutrition and growth during woodland establishment.
• What they did: In a fully-factorial field trial on former upland pasture (11.5 ha; ~25,000 saplings), soil inoculation and basalt amendment were tested in mixed-broadleaf and conifer plantations, with root and soil mycorrhizal fungi characterized in surrounding sources.
• The result: Soil inoculation caused only a subtle conifer EcM community shift (3% of variation) and none in broadleaves, while basalt amendment raised pH without changing mycorrhizal composition, diversity, or colonisation; root EcM shared more taxa with the nursery (41–48%) than donor inoculum (2–9%).