The properties of biomass-based fuel and combustion tests showed that logging residues are promising renewable energy sources. The data used in this study were collected from four clear-felling areas in Järvselja Training and Experimental Forest Centre, Southeast Estonia in 2013–2014. Logging was carried out by harvesters in Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies [L.] Karst.), silver birch (Betula pendula Roth.) and black alder (Alnus glutinosa L. Gaertn.) dominated stands with a small admixture of other tree species according to the cut-to-length method and logging residues were placed in heaps. The aim of this research is to assess different characteristics of logging residues (quantity, moisture content, energetic potential, ash content and amount) in clear-felling areas. The highest load of slash was measured on the birch dominated study site, where the dry weight of the logging residues was 29 t ha−1. Only the branch fraction moisture content on the black alder dominated site (35.4%) was clearly different from respective values on other sites (21.6–25.4%). The highest calorific value of the residues was assessed with the residues from the birch dominated site, where in moist sample it was 365 GJ ha−1 and in dry matter 585 GJ ha−1. The heating value of the fresh residues is highest in coniferous trees. The highest ash content in branch segments was registered for the black alder dominated site. Järvselja data indicate higher quality in conifer dominated sites, yet a higher load of logging residues in broadleaf dominated stands.
Alternatives to the restoration of cutaway peatlands include afforestation, energy forests, agricultural production, wetland restoration (restoration of peataccumulating function), reed canary grass (energy mower) or wild berries (blueberry, cranberry) cultivation, protected area for birds, and artificial lakes. Investigations made in several countries suggest that one of the most promising ways of regenerating cutaway peatlands is afforestation. The re-vegetation of Estonian cutaway peat production fields is mainly the result of natural processes, which are generally very slow: vegetation covers only 10–20% of a peat field. Carbon dioxide is not bound anymore in cutaway peatlands where vegetation layer has been destroyed and therefore photosynthetical processes no more occur. Using biofuel ashes (wood ash, etc.) for the afforestation of cutaway peatlands helps to balance the content of nutrients in peat substrate, which improves the survival of planted seedlings and significantly increases bioproduction. Drained and mined peatlands have become a significant source of CO2 but stimulated woody biomass production can be helpful to balance CO2 emission from cutaway peatlands. Because of the limited resources of fossil fuels and negative impacts on the environment in recent decades alternative sources of energy have been actively looked for. In Scandinavia a lot of attention has been paid to finding possibilities for using biofuels. The situation in Estonia is that only very few types of ashes (for example certified oil shale fly ash with product name Enefix) have been founded to be suitable for utilization and have been used for recycling in agriculture.
To investigate the ecosystems on dunes, five typical dunes were selected in the coastal area of the Baltic Sea in southwest Estonia. To study ground vegetation species richness, species composition and horizontal structure, 251 quadrats of 1 m2 in size were established and descriptions of vascular plants, bryophytes and lichen species were provided. Topographical factors, soil horizons, soil pH and electrical conductivity, soil nutrients, soil moisture conditions and light conditions were determined. In total, 42 vascular plant, 43 bryophyte and 48 lichen species were recorded on five dunes. Vascular plant species richness and composition on forested dunes was dependent on the absolute dune height, zone and aspect of the slope, soil nitrogen, potassium and phosphorus content, soil pH and moisture, the cover of the bryophyte-lichen layer and light conditions. Regarding bryophyte and lichen layer species composition, important factors were the aspect of the dune, vascular plant species cover, light conditions, the thickness of the moderately decomposed organic soil horizon, soil pH, electrical conductivity and volumetric water content. Lichen species richness was highest on the slopes of the dunes, while bryophyte species richness was higher at the bottoms and decreased towards the tops of the dunes. Ground vegetation species richness and species’ horizontal and vertical structure on forested dunes were highly dependent on topography-induced differences, aspect, height and zone of the dunes. The most important factors controlling the complex of ground vegetation were light conditions, soil water content, thickness of the moderately decomposed litter layer and soil potassium and calcium content.