Atmospheric carbon dioxide (CO₂) and tropospheric ozone (O₃) continue to increase since industrialization.  When primary production is altered from elevated CO₂ and O₃, this can cascade through trophic levels within an ecosystem, affecting the growth of heterotrophic organisms.  Ectomycorrhizal fungal growth and reproduction is dependent upon receiving carbon from host trees.  We have previously found that elevated CO₂ and O₃ can affect ectomycorrhizal fungal sporocarp production and community composition.  However, since ectomycorrhizal taxa can allocate different amounts of their acquired carbon into mycorrhizas, mycelium and sporocarps, the applicability of these results are hampered until a comprehensive view of the fungi, from the mycorrhizas to the sporocarps, is utilized.  Here we compare the community responses of ectomycorrhizas and sporocarps to elevated CO₂ and O₃ within Populus tremuloides stands at the Aspen FACE site in Rhinelander, Wisconsin.  Sporocarps and ectomycorrhizal root tips were harvested.  Ectomycorrhizas were molecularly analyzed for taxonomic identification.  The ITS region was amplified and analyzed by TRFLP.  One member from each TRFLP taxonomic group was sequenced.

Results/Conclusions

While the community composition of sporocarps was affected by CO₂ and O₃ levels, the composition of ectomycorrhizas remained unaffected.  Different taxa dominated the relative biomass of ectomycorrhizas and sporocarps.  Taxa within the Pezizaceae and Thelephoraceae contributed more to relative biomass as ectomycorrhizas than sporocarps.  These results suggest that elevated CO₂ and O₃ may affect sporocarp production more strongly than the distribution of taxa underground on root tips.