Mycorrhizal dominance influences tree species richness and richness-biomass relationship in China’s forests

Mycorrhizal associations drive plant community diversity and ecosystem
functions. Arbuscular mycorrhizas (AM) and ectomycorrhizas (EcM) are two
widespread mycorrhizal types and are thought to differentially affect
plant diversity and productivity by nutrient acquisition and plant-soil
feedback. However, it remains unclear how the mixture of two mycorrhizal
types influences tree diversity, forest biomass and their relationship at
large spatial scales. Here, we explored these issues using data from 1247
plots (600 m2 for each) across China’s natural forests located mostly in
temperate and subtropical regions. Both AM-dominated and EcM-dominated
forests show relatively lower tree species richness and stand biomass,
whereas forests with the mixture of mycorrhizal strategies sustain more
tree species and higher biomass. Interestingly, the positive effect of
tree diversity on biomass is stronger in forests with low (≤50%) than high
AM tree proportion (>50%), reflecting a shift from the
complementarity effect to functional redundancy with increasing AM trees.
Our findings suggest that mycorrhizal dominance influences tree diversity
and richness-biomass relationship in forest ecosystems.