Fungal diversity in Norway spruce (Picea abies) sapling roots in relation to forest regeneration and energy wood harvesting practices

Background/Question/Methods

Energy wood harvesting has increased rapidly in recent years, although its impacts on soil biodiversity and forest regeneration are largely unknown. We quantified the contribution of energy wood harvesting on the composition of soil fungal community, especially the ectomycorrhizal fungi in Norway spruce (Picea abies) saplings. The aims of the study were to assess (i) spruce sapling growth and (ii) root fungal diversity and ecological grouping in relation to energy wood harvesting treatments. Nursery seedlings of Norway spruce were planted in 2008 in four treatments: 1) uncut forest control, 2) clear-cut + patch mounding, 3) clear-cut + 70 % logging residue removal + patch mounding, 4) clear-cut + 70 % logging residue removal + stump removal (25 stumps/ha left) + patch mounding. The experiment was established in three locations; south, central and north Finland in the boreal vegetation zone. Saplings were harvested in September 2011, their growth parameters measured, and root fungal communities studied by 454 pyrosequencing. For fungal identification, the obtained sequences were compared to open databases (GenBank, UNITE) using the BLAST tool.

Results/Conclusions

In all locations (south, central, north), uncut forest control differed substantially from other treatments both in terms of sapling growth (lower in the control compared to all other treatments) and fungal community composition. Most common species in the whole data was Thelephora terrestris, possibly of nursery origin, with 53.6 % of obtained sequences. In the uncut forest control, Piloderma spp., Russula spp., and Cortinarius spp., were abundant. In the treatments 2, 3 and 4 the fungal communities were dominated by Thelephora terrestris. Other abundant taxa, in these three treatments, were Tylospora asterophora, Tylospora fibrillosa, Wilcoxina sp., Amphinema byssoides, Helotiales sp., Meliniomyces and Phialocephala helvetica. The number of fungal OTUs was highest in the uncut controls, and no differences were found within the other treatments.

Most diverse fungal communities were found in the roots of the smallest saplings grown in the uncut spruce forest, while the other treatments provided larger saplings associated with fungal communities dominated by Thelephora terrestris. Mobilization of soil nutrients, changed inoculum potential and soil disturbance in the treatments with forest clear-cut are suggested to explain the results.