Species-specific measurements of ectomycorrhizal turnover under N-fertilization: combining isotopic and genetic approaches.

Ectomycorrhizal fungi play a significant role in the transfer of nutrients between plant and soil pools. Here we combine natural abundance (14)C measurements with restriction fragment length polymorphism (RFLP) to study the effects of nitrogen fertilization on the residence time of carbon within ectomycorrhizal species. We show that the carbon in ectomycorrhizal fungi turns over every 4-5 years, indicating that these fungi are relatively long-lived. Moreover, ectomycorrhizal fungi responded in a species-specific way to fertilization. Cenococcum geophilum contained younger carbon on average in nitrogen-fertilized plots than in control plots, even though turnover rates of the community as a whole did not shift significantly. Our results suggest that the response of ectomycorrhizal fungi to N availability is complex, and alterations in tissue turnover within this microbial pool may vary depending on community structure.