Finnish Forest Research Institute  Metla

Press release 16.08.2006

Ectomycorrhizal fungi associated with growth rate of trees

Ectomycorrhizal fungi (ECM) are vitally important to the growth and wellbeing of trees; the diversity of ECM species is enormous, though the number of their host tree species is but a few. The diversity of tree species is known to have an effect on the underground mycorrhizal community but the effect of variation between individual trees of the same species on the mycorrhizal community is largely unknown. According to the study conducted by the Finnish Forest Research Institute (Metla), the growth rate of trees is associated with the diversity of the ECM community and structure. The results indicate that for tree growth, more important than the size or morphology of the root system is the ECM community structure.

The results showed that the more diversified the ECM community was, the faster the host tree grew. In slow-growing spruce clones the diversity of ectomycorrhizae was less than in fast-growing trees. In addition, certain differences were found in the ECM community structures in spruce clones of similar growth rate. In fast-growing spruce clones the proportion of fungi forming abundant mycelia outside the roots was greater than that in slow-growing clones. No correlation was found between ectomycorrhizal diversity and the density and degree of branching of the fine-roots. The variation in mycorrhizal communities of individual trees also indicate that the great ECM diversity in boreal forests and the patchy distribution of them may be partly related to the impact of individual trees on the ECM community. The field trials were made using eight different Norway spruce (Picea abies (L.) Karst) clones and their ECM communities. The trials were performed on a clear cutting area established in 1994 by the Foundation for Forest Tree Breeding, and the study plots were randomly organized into replicate blocks. The mycorrhizal samples were collected in autumn 2003 and the strains were determined using molecular identification.

The research was part of the Metla project ”The impact of genotype of Norway spruce on mycorrhizal fungal community and function of boreal forest soil decomposer microbes”

Publication: T. Korkama, A. Pakkanen and T. Pennanen. 2006. Ectomycorrhizal community structure varies among Norway spruce (Picea abies) clones. New Phytologist 171: 815–824.

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