N concentration controls decomposition rates of different strains of ectomycorrhizal fungi

The decomposition of soil organic matter in forest ecosystems is important in two ways. First, soil organic matter is the largest pool of C in terrestrial ecosystems, so understanding global carbon cycling requires an appreciation of the factors that control the size of that pool and the fluxes through it. Among these factors are those that control the rate of organic matter decomposition. Second, organic matter decomposition is the major process controlling the supply of nutrients to plants. In some ecosystems ectomycorrhizal fungi comprise a surprisingly large fraction of soil organic matter. However, little is known of the rates of decomposition of ectomycorrhizal fungi, or of the factors that control those rates. Therefore, we set out to examine the relationship between N concentrations and decomposition rates of ectomycorrhizal fungi using a wide variety of strains isolated from a Pinus resinosa plantation. We found that substantial variation among strains existed in decomposition rate, and that decomposition rate was highly correlated with tissue N concentration. We conclude, therefore, that the structures of ectomycorrhizal fungal communities may be ecologically important in terms of ecosystem C and N dynamics.