Mycorrhizal type shapes climatic dependence and evolutionary rates of woody plant biomass responses to drought

Almost all woody plants form symbiotic associations with mycorrhizal fungi, but how different mycorrhizal types may modulate tree drought responses remains unresolved. Here, we conducted a global phylogenetic meta-analysis coupled with evolutionary rate calculations on biomass responses to experimental drought in 232 arbuscular mycorrhiza (AM) and ectomycorrhiza (EcM) woody species. Our results showed that the biomass of EcM plants was less sensitive to mild drought than that of AM plants, whereas AM plants showed weaker biomass declines under severe drought. Over evolutionary history, both mycorrhizal types have evolved towards increasing drought tolerance, with faster rates in EcM species. The adaptive ability of EcM plants was disrupted by severe drought due to diminished nutrient-acquisition capacity and limited carbon supply. These results imply a potentially water condition-dependent nonlinear shift in the relative abundance of AM and EcM trees, which could have critical consequences for global forest functioning in the Anthropocene.