Linking the functional diversity of ectomycorrhizal fungal species to soil carbon dynamics and the genetics of a foundational tree species

Background/Question/Methods

Increasing carbon dioxide in our atmosphere due to anthropogenic factors has led to an increased interest in the ability of ecosystems to act as carbon sinks.  Ectomycorrhizal fungi (EMF) are symbionts of trees and link plants to soil carbon pools. Understanding the role that EMF play in soil carbon storage could provide the mechanism for how soil can act as a carbon sink.  Studies have shown that not only are EMF communities speciose and variable over space and time, but EMF species vary in functional traits such as exploration strategy and enzymatic activity, both of which can affect soil carbon dynamics.  We studied variation in EMF species and functional diversity (exploration types and enzyme activities) among longleaf pine genetic families in an experimental forest in southern Mississippi.  We counted EMF morphotypes and determined their exploration types.  Species identities were confirmed using molecular techniques.  The most dominant EMF species in each sample were assayed for the activity of enzymes involved in the degradation of cellulose (β-1,4-glucosidase and cellobiohydrolase), chitin (β-N-acetylglucosaminidase), hemicellulose (β-1,4-xylosidase), nucleic acids (phosphatase) and lignin (phenol oxidase and peroxidase). 

Results/Conclusions

We found significant differences in ECM community composition among longleaf pine families.  We also found significant differences in β-1,4-glucosidase, β-N-acetylglucosaminidase and phosphatase activities between dominant ECM fungal species and among particular longleaf pine families. These results suggest that selection of particular longleaf pine genotypes could alter the community composition and function of ECM fungi in managed southern pine forests, with important consequences for soil C sequestration.