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Abstract: We used PCR-DGGE fingerprinting and direct sequencing to analyse the response of fungal and actinobacterial communities to changing hydrological conditions at 3 different sites in a boreal peatland complex in Finland. The experimental design involved a short-term (3 years; STD) and a long-term (43 years; LTD) water-level drawdown. Correspondence analyses of DGGE bands revealed differences in the communities between natural sites representing the nutrient-rich mesotrophic fen, the nutrient-poorer oligotrophic fen, and the nutrient-poor ombrotrophic bog. Still, most fungi and actinobacteria found in the pristine peatland seemed robust to the environmental variables. Both fungal and actinobacterial diversity was higher in the fens than in the bog. Fungal diversity increased significantly after STD whereas actinobacterial diversity did not respond to hydrology. Both fungal and actinobacterial communities became more similar between peatland types after LTD, which was not apparent after STD. Most sequences clustered equally between the two main fungal phyla Ascomycota and Basidiomycota. Sequencing revealed that basidiomycetes may respond more (either positively or negatively) to hydrological changes than ascomycetes. Overall, our results suggest that fungal responses to water-level drawdown depend on peatland type. Actinobacteria seem to be less sensitive to hydrological changes, although the response of some may similarly depend on peatland type. [Copyright &y& Elsevier]

The formation of the organic layer within Scandinavian forest soil started about 10000 yr ago, following the retreat of the continental ice sheet. Since then the land has been slowly rising in northern Europe and uplift still occurs on the coast of the Bothnian Bay at a rate of about 0.6-0.9 m per 100 yr. Four, 300 m long, successional gradients were studied from the shoreline to a Scots pine (Pinus sylvestris) stand with a fully developed humus layer of a few centimetres' thickness. The plantless shoreline was followed by small foredunes and dunes, characterized by Agrostis stolonifera and Leymus arenarius, respectively, and the deflation basin characterized by lichens and sparse Festuca ovina and Deschampsia flexuosa. The study sites situated in Scots pine stands of about 25 and 40 yr age were characterized by sparse dwarf shrubs, lichens and bryophytes. The amount of organic matter in soil increased along the gradient. When the microbial biomass, estimated as indicative phospholipid fatty acids (PLFAs), was calculated on the organic matter basis, the total microbial biomass as well the amount of bacterial PLFAs decreased from the earlier stages of succession towards the pine forest. The ratio of fungal to bacterial PLFAs increased along the succession. The bacterial community structure in the shore soil was different to that in the dune soil or in forested zones. On the plantless shore the microbial community was almost completely described by PLFAs indicative of Gram-negative bacteria. In addition to these bacterial PLFAs, dunes were characterized by PLFAs indicative of actinomycetes. Thus, the fungal part of the microbial community seemed to respond most to the accumulation of organic matter and increasing C/N ratio, while the bacterial biomass and bacterial community structure seemed also to reflect the composition of the vegetation and the varying quality of the organic matter. [ABSTRACT FROM AUTHOR]

Responses of soil decomposer animals (enchytraeids and microarthropods) to wood-ash fertilisation (1000 and 5000 kg ha[sup -1]) and a fire treatment mimicking prescribed burning were studied in a Scots pine stand in central Finland. The experiment was conducted on 30 x 30 m² plots, each treatment being replicated four times. Soil animals were sampled throughout the growing season in the third year after the treatments. As a rule, numbers of soil animals increased during the study period. Numbers of the only enchytraeid worm species found at the study site, Cognettia sphagnetorum, were lower in the plots with higher ash level and plots which have been burned, in the plots having these treatments, enchytraeid populations increased during the study period. Total numbers of microarthropods were decreased in the plots which had received the most drastic treatments: the higher ash level and burning. Only five species of collembolas responded significantly to these treatments. Multivariate analyses showed, however, significant changes in the collembola community structure of all the treatments. Overall, soil fauna seemed to be quite resistant and resilient against unpredictable disturbances, like ash fertilisation and prescribed burning, the thick humus layer being a major buffer against chemical and physical changes. [ABSTRACT FROM AUTHOR]

• Wood discs were incubated 4 years on a forestry induced soil disturbance gradient. • The forestry treatments were not reflected in the decomposition rate. • The increase in fungal species diversity was associated to the wood decay process. • Parallel increase in decomposition rate with white rot and mycorrhizal OTU number. • Wood discs received fungal inoculum from both soil and air. The current requirements to decrease the consumption and greenhouse gas emissions of fossil fuels have increased the demand of renewable energy sources. In forestry, this situation has intensified harvesting practices resulting in a decreased amount of woody debris left on the clear-cut areas. Impacts of energy wood harvest on wood-decomposing fungi were studied in a large-scale experiment in clear-cut stands in three geographical areas in Finland. A sequence of treatments was expected to form a forestry induced soil disturbance gradient: (1) logging residues left at site, no soil preparation; (2) logging residues left at site, patch mounding; (3) 70% logging residue removal, patch mounding; and (4) complete stump and logging residue removal, patch mounding. Pre-weighed wood discs were incubated on the intact soil cover for four years to estimate decomposition rate and fungal decomposer community. A soil sample was taken underneath each disc to evaluate the direct inoculation potential of the soil. The main results were as follows: (1) The differences between the treatments were not significant, while the geographical factors affected the decomposition rate and the fungal communities of the wood discs. (2) The fungal composition in the wood discs did not reflect the underlying soil fungal community, which indicates that a part of the fungal species inhabiting wood discs originated from airborne surrounding sources. (3) The increase in fungal species diversity was associated to the wood decay process, indicated by parallel increase in the wood decomposition rate and the number of white rot and mycorrhizal fungi. Thus our study indicates that in addition to local environment, landscape-level factors control the decomposer fungal community and its activity in wood. [ABSTRACT FROM AUTHOR]

Nitrogen (N) accumulation rates in peatland ecosystems indicate significant biological atmospheric N2 fixation associated with Sphagnum mosses. Here, we show that the linkage between methanotrophic carbon cycling and N2 fixation may constitute an important mechanism in the rapid accumulation of N during the primary succession of peatlands. In our experimental stable isotope enrichment study, previously overlooked methane-induced N2 fixation explained more than one-third of the new N input in the younger peatland stages, where the highest N2 fixation rates and highest methane oxidation activities co-occurred in the water-submerged moss vegetation.

Fungal and actinobacterial communities were analyzed together with soil chemistry and enzyme activities in order to profile the microbial diversity associated with the economically important mushroom Tricholoma matsutake. Samples of mycelium-soil aggregation (shiro) were collected from three experimental sites where sporocarps naturally formed. PCR was used to confirm the presence and absence of matsutake in soil samples. PCR-denaturing gradient gel electrophoresis (DGGE) fingerprinting and direct sequencing were used to identify fungi and actinobacteria in the mineral and organic soil layers separately. Soil enzyme activities and hemicellulotic carbohydrates were analyzed in a productive experimental site. Soil chemistry was investigated in both organic and mineral soil layers at all three experimental sites. Matsutake dominated in the shiro but also coexisted with a high diversity of fungi and actinobacteria. Tomentollopsis sp. in the organic layer above the shiro and Piloderma sp. in the shiro correlated positively with the presence of T. matsutake in all experimental sites. A Thermomonosporaceae bacterium and Nocardia sp. correlated positively with the presence of T. matsutake, and Streptomyces sp. was a common cohabitant in the shiro, although these operational taxonomic units (OTUs) did not occur at all sites. Significantly higher enzyme activity levels were detected in shiro soil. These enzymes are involved in the mobilization of carbon from organic matter decomposition. Matsutake was not associated with a particular soil chemistry compared to that of nearby sites where the fungus does not occur. The presence of a significant hemicellulose pool and the enzymes to degrade it indicates the potential for obtaining carbon from the soil rather than tree roots.