7. Treeline conifer ectomycorrhizae

Effects of elevated CO₂ and defoliation stress on diversity of ectomycorrhizae of treeline conifers were studied by planting four month old sterile seedlings of Larix decidua and Pinus uncinata as probes under adult trees of the same two species for the 2003 growing season. According to ITS-RFLP typing, 20 ectomycorrhizal fungi were identified including 10 Larix-specific, 8 Pinus-specific and 2 unspecific morphotypes on conifer hosts. Increased atmospheric CO₂ concentration led to an increase in the number of morphotypes and diversity of morphotypes observed on Pinus seedlings but not on larch seedlings. Rhizomorph occurence increased on roots of both of the seedling species growing in plots exposed to elevated CO₂ with the exception of those growing under defoliated trees of the opposite host species. These results suggest that increases in atmospheric CO₂ concentrations may impact below-ground processes creating potential feedbacks at the ecosystem level. Four morphotypes that were discovered at the site are shown in the photographs.