Abstract Understorey herbaceous plants are a vital component of forest biodiversity in temperate forests. However, the mechanisms underlying their community assembly and species coexistence remain poorly understood. This study investigates how environmental conditions and mycorrhizal symbiosis across different forest strata influence herb diversity in a temperate forest region. This study used data from 437 temperate forest plots spanning environmental gradients. Within the Hill–Chao framework, we calculated herb species and phylogenetic diversity indices. We then explored the specific pathways through which environmental factors and mycorrhizal associations influence herb diversity. Herb species and phylogenetic diversity were positively correlated and showed largely consistent responses to mycorrhizal symbiosis. Herb community mycorrhization promoted herb diversity. Greater ectomycorrhizal (EcM) tree dominance significantly reduced herb diversity. Notably, mixed‐mycorrhizal tree communities supported the highest levels of herb diversity. Climate, particularly precipitation, shaped the spatial distribution of mycorrhizal status and types, thereby indirectly influencing herb diversity. Soil total nitrogen affected herb diversity indirectly through its influence on EcM tree dominance. By disentangling the complex relationships between mycorrhizal symbiosis across forest strata and herb diversity along ecological gradients, this study contributes to a better understanding of species coexistence in forest ecosystems. Read the free Plain Language Summary for this article on the Journal blog.
Li et al. (Sat,) studied this question.