Thu, Aug 05, 2021:On Demand
Background/Question/Methods
Ectomycorrhizal fungi are central members of the forest fungal community, forming symbiosis with most trees in temperate and boreal forests and enhancing plant access to limiting soil nutrients. Decades of greenhouse studies have shown that tree seedlings acquire more nitrogen and grow faster in combination with specific ectomycorrhizal fungi, and that these effects are sustained when seedlings are out-planted into regenerating forests. Whether fungal effects observed between tree seedlings and individual ectomycorrhizal fungi scale up to affect the growth of mature trees and entire forests harboring diverse fungal communities remains unknown. In this study, we combined a continental set of European forest inventory data from the ICP forest network with molecular ectomycorrhizal fungal community surveys to identify potential fungal mediated effects on forest productivity and paired this alongside a tree growth response to microbiome manipulation study conducted under controlled conditions.
Results/Conclusions We found that ectomycorrhizal fungal community composition was a key predictor of tree growth, and this effect was robust to statistically accounting for climate, nitrogen deposition, soil inorganic nitrogen availability, soil pH, and forest stand characteristics. We also linked ectomycorrhizal fungal community members with genomic functional potentials and found higher fungal energy production and inorganic nitrogen metabolism but lower organic nitrogen acquisition enzyme encoding gene proportions in fast versus slow growing forests. Lastly, we sampled soils from fast and slow growing forests and introduced their microbiomes into a sterilized growth medium to experimentally isolate microbiome effects on tree development. Consistent with our observational analysis, tree seedling growth was accelerated in tandem with microbiomes from fast growing compared to slow growing forests and was correlated with ectomycorrhizal community composition. By linking molecular community surveys and long-term forest inventory data in the field and pairing this with a microbiome manipulation study under controlled conditions, this work demonstrates an emerging link between the forest microbiome and forest productivity.
Results/Conclusions We found that ectomycorrhizal fungal community composition was a key predictor of tree growth, and this effect was robust to statistically accounting for climate, nitrogen deposition, soil inorganic nitrogen availability, soil pH, and forest stand characteristics. We also linked ectomycorrhizal fungal community members with genomic functional potentials and found higher fungal energy production and inorganic nitrogen metabolism but lower organic nitrogen acquisition enzyme encoding gene proportions in fast versus slow growing forests. Lastly, we sampled soils from fast and slow growing forests and introduced their microbiomes into a sterilized growth medium to experimentally isolate microbiome effects on tree development. Consistent with our observational analysis, tree seedling growth was accelerated in tandem with microbiomes from fast growing compared to slow growing forests and was correlated with ectomycorrhizal community composition. By linking molecular community surveys and long-term forest inventory data in the field and pairing this with a microbiome manipulation study under controlled conditions, this work demonstrates an emerging link between the forest microbiome and forest productivity.