Metla Project 3300

The effect of mycorrhizal inoculum on the growth and survival of the spruce seedlings

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Duration: 2000-2006   Keywords: Norway spruce, mycorrhiza, nursery
Research project group: Distinct projects 1 - Structure and function of forest ecosystems


The aim of this research project is to find mycorrhizal fungi to promote the growth and survival of Norway spruce (Picea abies) seedlings. During the first growing seasons a selection of mycorrhizal fungi will be isolated from different kind of environments. The ability of the isolated fungi to infect spruce seedlings will be confirmed by laboratory experiments and the mycorrhizal strains will be identified by DNA-sequence analyses. The suitability of commonly applied fertilization levels for mycorrhizal growth will be examined. The ability of the isolated mycorrhizal fungi to promote growth of the spruce seedlings will be tested using field experiments. The seedlings infected with various mycorrhizae will be grown for 1 -1,5 years at the nursery utilizing the previous results of the suitable fertilization levels and growing media. Seedlings will be planted in the field and the growth and survival of the seedlings will be followed yearly. The results of this project will enable evaluation of the significance of mycorrhizal fungi inoculations on the early development of Norway spruce seedlings. If the results are promising the research will be continued in order to develop a commercial mycorrhiza inoculum for spruce seedlings in nurseries.

The national mycorrhiza meeting for researchers was organized at Metla 19.-20.4. 2004 (see abstracts)


About 50 ECM strains were isolated within the project. Nearly all the ECM isolates originating from the root tips of very young spruce seedlings were inconspicuous ECM species, mostly corticioid basidiomycetes and ascomycetes, and few thelephoroid basidiomycetes. Many of these strains showed to be promising in promoting growth of the seedlings in the nursery and after planting. Three field experiments were established in the project. In the field experiments established in 2003 and 2004 we found four ECM strains which improved the growth of the seedlings significantly (20-40%) compared to the uninoculated control seedlings (Pennanen et al. 2004 and Pennanen et al., manuscripts in preparation). Seedlings inoculated altogether with seven different ECM strains did show improved growth (10-20%) after two and three years after outplanting. The third field experiment emphasizes the impact of the nursery ECM on the spruce seedlings in comparison to forest ECM species. The preliminary results from this experiment indicate that the ECM common in the nurseries all over the world (Thelephora terrestris) has negative effect on the seedling performance in the field. We also performed a survey on the degree of mycorrhizal colonization and species composition in different forest nurseries in Finland. In Finnish nurseries, great differences in ECM colonization were observed. In general, colonization degree of the seedlings was poor (0-19% and 0-66% in one- and two-year old seedlings, respectively). Both ECM colonization degree and ECM species richness were negatively correlated with the fertilization rates and the use of herbicides (Flykt et al. 2004)

In addition, a few years ago our research group posed the following question - Does genetic variation within tree species control diversity and the function of the associated ECM community and soil decomposer microbes? Our results from a Picea abies clonal trial, established in a forest clear-cut in 1994, demonstrated significant differences in the ECM communities among and also within clone groups showing twofold differences in growth (Korkama et al. 2006). These results showed a trend for positive correlation between ectomycorrhizal diversity and tree growth. Our results also found differences between plots with slow and fast growing clone in respect to distribution of external mycelia of ECM fungi, and the structure of soil microbial community. Litter decomposition rates under the different clone groups were similar, implying that differences in nutrient turnover were not a direct reason for the differences in growth rates of the clones (Korkama et al., manuscripts in preparation). The results suggest that the spatial patchiness of soil microbes even in monospecific stands is partly explained by genetic variation of trees.

Project leader: Pennanen, Taina
The Finnish Forest Research Institute, Vantaa Unit, PL 18, FI-01301 VANTAA, FINLAND
Phone: +358 29 532 5469

Other researchers: Hantula, Jarkko, VA (2004), Jaatinen, Krista, VA (2006), Korkama, Tiina (2003-06), Müller, Michael, VA (2002-04)

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Updated 12.06.2012