Carbon isotopes in sporocarps from the Swiss conifer web-FACE, 2010-2011

The spatial extent and lag time of carbon fluxes to ectomycorrhizal fungi associated with differing hyphal development and hosts could provide insights into forest carbon dynamics. In ectomycorrhizal sporocarps collected at 0-6, 6-12, 12-18, and > 18 m from five 13CO2-labeled Picea abies, δ13C patterns were analyzed. At 0-6 m, taxa with greater or lesser hyphal development derived 25 ± 7% and 48 ± 7% of their carbon from labeled trees, respectively. At 6-12 m, conifer-associated and other-associated sporocarps derived 74 ± 6% and 5 ± 6% of their carbon from labeled trees, respectively. Sporocarp δ13C correlated positively with solar radiation for 17-21 days prior to sporocarp harvest. These patterns indicated that (1) carbon accumulation and movement for sporocarp formation took several weeks, (2) Picea photosynthate was preferentially allocated to conifer-associated fungi, and (3) taxa of greater hyphal development assimilated carbon more widely than taxa of less hyphal development.