Saana Kataja-aho

Effects of stump removal on soil decomposer communities in undisturbed patches of the forest floor.

Abstract Soil preparation after clear-cutting leads to fragmentation of forest floor and, consequently, changes the habitat of decomposers. Stump removal for bioenergy is further increasing the disturbance in the soil. We studied responses of decomposers to stump removal in boreal spruce forests during the first 4 years after clear felling in relation to mounding. Samples for each decomposer organism group were taken from undisturbed forest floor patches that are the main habitat for decomposers after forest regeneration and whose amount and size obviously differ between the treatments. Microbial biomasses and community structure, and the abundance of enchytraeids, were not found to be affected by the stump removal. The abundance of nematodes and the total numbers of collembolans were lower in the stump harvesting plots compared with the mounded plots 3 years after the regeneration. In addition, microbivorous macroarthropods had higher abundances in the mounded plots. Together, decomposer community in the fragments of undisturbed forest floor only slightly differed between the mounded and stump removal areas. However, more data are urgently needed to also find out the longer-term effects of stump removal on the forest soil decomposers and their functioning and the development of decomposer community in exposed mineral soil.

Does stump removal affect early growth and mycorrhizal infection of spruce (Picea abies) seedlings in clear-cuts?

Abstract Stump removal procedure increases the extent of exposed mineral soil in the clear felled areas. In this study, our aim was to find out whether the early growth and mycorrhization of Norway spruce (Picea abies (L.) Karst.) seedlings differ between stump removal and mounding sites. Stumps were harvested from five one-hectare study sites and other five sites were mounded after clear felling. Twenty seedlings were planted on mounds at each study site. Although the height of spruce seedlings did not differ between the treatments after three growing periods, their mean growth was ca. 10% higher at the stump removal sites. The community of ectomycorrhizal (ECM) in the seedling roots did not differ between the treatments. The high mycorrhization rate in the nursery still remained after two and three growing seasons in the field and diversity of ECM community slightly increased during the first years. Our results indicate some positive although rather small and transient effects of stump removal on the performance of planted spruce seedlings. Longer-term studies are needed to fully understand the effects of stump removal on the later seedling development and their symbiotic interactions with mycorrhizal fungi.