New research from China's Baotianman Nature Reserve shows that forests dominated by ectomycorrhizal trees, like pines and oaks, store more aboveground biomass than those with more arbuscular mycorrhizal species. The study, published in BMC Plant Biology, found that the relative abundance of large ectomycorrhizal trees explained 42.66 percent of the fixed-effect variation in aboveground biomass. But that carbon gain comes with a catch: species richness and tree-size variation both declined as ectomycorrhizal trees took over. The trade-off matters for forest carbon projects. If you only measure biomass, you may reward stands that are simpler and less diverse, while missing the indirect drag that diversity loss creates. The study used structural equation modeling to separate direct and indirect effects, and the indirect effects of ectomycorrhizal abundance on biomass were negative. For anyone building baselines for forest carbon credits, fungal community composition is not a minor detail.
