Abstract:

Objective: This study aims to explore the regulatory effects of ectomycorrhizal (EcM) tree species dominance on tree species richness and stand aboveground biomass, so as to provide scientific support for the sustainable management of temperate forest ecosystems. Method: Based on 2?224 forest inventory plots in Jilin Province, the basal-area proportion at breast height of EcM tree species was calculated to characterize EcM tree species dominance. Combined with topographic, climatic and edaphic environmental factors, generalized linear mixed-effects models (GLMMs) and structural equation models (SEMs) were applied to investigate the impact of EcM tree species dominance on tree species richness and stand aboveground biomass. Result: 1) The stands dominated by EcM tree species exhibited relatively low tree species richness, while the stands with mixed mycorrhizal strategies (EcM tree species proportion approximately 51.7%) had the highest species richness. For stands with tree species richness >?6, EcM tree species dominance exerted a stronger positive effect on stand aboveground biomass. Within stands with high EcM tree species dominance (>?50%), the positive influence of tree species richness on aboveground biomass was greater than that in forests with low EcM tree species dominance (≤?50%). 2) The analysis results with GLMMs showed that the dominance of EcM tree species, and its interaction with tree species richness, as well as soil organic carbon density exerted significant (P<0.05) negative effects on stand aboveground biomass. In contrast, the quadratic term of EcM tree species dominance, tree species richness, stand mean age, slope, soil total nitrogen content and latitude had significant (P?<?0.05) positive effects. 3) SEMs analysis indicated that biotic factors (i.e., EcM tree species dominance and its quadratic term, tree species richness, and stand mean age) imposed greater impacts on stand aboveground biomass than environmental factors. Tree species richness and stand mean age consistently showed positive effects on stand aboveground biomass. As tree species richness increased, the total effect of the quadratic term of EcM tree species dominance shifted from negative to positive. Conclusion: Mixed mycorrhizal strategies facilitate tree species richness in temperate forest ecosystems, and EcM tree species dominance promotes the accumulation of stand aboveground biomass. EcM tree species dominance modulates the relationship between tree species richness and stand aboveground biomass. This study highlights the importance of EcM tree species dominance for forest diversity and aboveground biomass accumulation, which is critical for maintaining and enhancing the functions of temperate forest ecosystems.

Key words: mycorrhizal dominance, ectomycorrhiza, biomass, species richness-biomass relationship, temperate forest