Forests and the forest-based sector play important roles in mitigating climate change through carbon sequestration and storage in living biomass and soil. In Europe, the forest sector is the only sector that positively affects atmospheric carbon balance. After the forest harvest, a large share of carbon is removed together with the wood. This wood carbon might be stored for centuries if in the form of long-lived wood products. In 2011, the United Nations decided that countries should account for and report carbon balance not only in forests but also in harvested wood products (HWP), followed by very general guidelines on methods for carbon accounting in HWP. The Intergovernmental Panel on Climate Change (IPCC) proposed three methodological levels called tiers for estimating carbon stock and its changes in HWP. The first reporting period revealed that countries applied different carbon accounting methods (tiers), therefore comparing the carbon budgets of HWP and the effect of climate change mitigation among different countries is difficult. In order to test the differences between carbon accounting methods proposed by the IPCC guidelines, we applied two carbon accounting methods and used different data sources in the case of Lithuania. The methods applied were the IPCC Tier 2 method (data on HWP from statistics or the literature, default half-life values, and default HWP categories) and material flow analysis, which is compatible with the IPCC Tier 3 method (material flow data on HWP, country-specific half-life values, and country-specific HWP categories). Depending on the availability of historical data from different sources for the purpose of this study, three study periods were defined: 1992–2015 Food and Agriculture Organization Corporate Statistical Database (FAOSTAT) data, 1960–1991 data from the literature, and 1940–1991 data from national statistics. The study findings show that carbon stock in HWP significantly differed when different data sources and methods were applied. The highest carbon stock in HWP (19.5 Mt) at the end of the study period was observed when FAOSTAT data from 1992–2015 were used and the Tier 3 method was applied. The lowest carbon stock in HWP (11.2 Mt) at the end of the study period was observed when data from national statistics from 1940–1991 were used and the Tier 2 method was applied. The carbon inflow into the pool of HWP in all cases was estimated to be 40% higher when material flow analysis was applied compared to the IPCC default (Tier 2) method. These findings suggest that in general it is more reasonable to apply the Tier 3 method for carbon accounting of HWP in Lithuania.

Background and Objectives: The aim of this study was to determine the effects of different stand densities on wood density (WD), global modulus of elasticity (MOE), and bending strength (MOR) in 35-year-old Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) H. Karst) stands, representing the hemiboreal forest zone. Materials and Methods: Scots pine and Norway spruce sites, representing different stand densities of 3000–3100; 2000–2100 and 1000–1100 trees per hectare, were chosen. Visually healthy model pine and spruce trees were selected, and diameter at breast height (DBH) was measured for model trees; the competition index was calculated; the MOE and MOR were evaluated by the Standards EN 408:2006 and EN 384:2016, at 12% moisture content; WD and the knot diameter were measured; and the strength class of wood was determined by the Standard EN 338:2009. To predict wood quality characteristics based on stand and tree characteristics, linear regression models were developed. Results and Conclusions: Higher stand density led to a significant change in the main wood properties of both conifer species. The highest mean WD, MOE, and MOR were obtained at the sites with the highest stand density. The MOE and MOR were highly correlated, but relatively weak correlations were found between MOE and MOR with tree DBH and WD. Despite the lower quality of Scots pine wood, the Norway spruce wood from more dense sites corresponded to the strength class of C16, according the strength grading of softwoods. The linear regression models did not perform well in describing the relationship of wood properties with stand and tree characteristics. The models for MOR accounted for the highest variation of 62–65% for both Scots pine and Norway spruce. These relationships can be expected to change with increased stand age or with the inclusion of specific crown parameters.

Climate change and transition towards a bioeconomy are seen as both challenges and opportunities for the forest-based sector in Europe. Transition towards a bioeconomy will in most cases rely on intensified use of renewable resources and/or advancement in technology. However, how can the intensified use of renewable resources be combined with climate change mitigation measures to increase carbon sinks in the forest-based sector? Additionally, what are the possible socio-economic and environmental impacts of intensified wood use? In this study, we examined the impacts of increased wood utilisation in Lithuania. The objective of this study was to assess the effects of increased domestic wood utilisation on: (i) employment; (ii) the economic performance of the sector; (iii) carbon in forest biomass and soil; and (iv) carbon in harvested wood products (HWP). The system boundaries were set in accordance with international greenhouse gas reporting to include only domestic wood flows. We assessed alternative wood utilisation scenarios using a forest resource model and a tool to assess sustainability impacts of (wood) value chains, using country specific data on wood (carbon) flows. Our results indicate that increased wood use could lead to trade-offs between six selected indicators. Opportunities for employment and the economic performance of the forest-based sector improved in all scenarios due to increased wood utilisation. However, when forest fellings increased, the carbon stored in forests decreased, the carbon stored in HWP increased, but overall the total carbon stored in forests and HWP decreased. When considering also additional substitution effects until the year 2100, the scenario with reduced wood exports generated larger total climate change mitigation effects than the baseline. Our results suggest that increased wood utilisation might support Lithuania's bioeconomy through increased socio-economic benefits. National positive climate change mitigation effects could be gained only if additional actions to utilise more domestic wood for long-life HWP will be taken.

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The European beaver Castor fiber is well‐known as an ecosystem engineer that greatly affects landscape structure, biodiversity as well as physical and chemical properties of surface water bodies. Beaver ponds alter surface water bodies by raising water elevation, decreasing flow velocity and altering the morphology of streams or drainage ditches, which can reduce the concentrations of organic carbon (OC) and nutrients (N, P). Recent studies indicated that mercury transforms into hazardous and neurotoxic methylmercury (MeHg) in beaver impoundments by biological processes in anaerobic conditions. However, the knowledge about nutrients and MeHg levels in impounded forest waterbodies is scarce in Lithuania. We aimed to ascertain the alteration in concentrations and stocks of OC, nutrients and MeHg in water and sediments from upstream and downstream, as well as within beaver dams and ponds during the growing seasons of 2016–2018. Results showed higher concentrations of dissolved organic carbon (DOC) and nutrients (P and N) in upstream water samples compared to those of downstream from beaver dams. Meanwhile, in sediments mean stocks of OC, P and N were the highest in the middle part of the ponds and in beaver dams. Moreover, the concentrations and stocks of MeHg in sediments were higher in beaver dams than in any other parts of beaver impoundments (upstream, mid‐pond, pond periphery and downstream). We conclude that dam bottom sediments were rich in OC, N and P, and at the same time, contained toxic MeHg. Therefore, beaver dams could act as a trickle filter by improving water quality, in our case, DOC, N and P leaching, from riparian forests and soils, but may also act as hotspots of mercury methylation.

Background and Objectives: The aim of this study was to determine the effects of different stand densities and thinning regimes on stem quality parameters, mainly branch characteristics, of Scots pine (Pinus sylvestris L.) trees. The study provides some input to the discussion about Scots pine stem quality responses to different forest management practices in relatively young stands. Materials and Methods: Total tree height, height to the lowest live and dead branch, diameter at breast height (DBH), and diameter of all branches from the whorls located up to 6 m from the ground were measured. The linear regression models to predict branch diameter, as the main parameter for the stem quality assessment, were developed based on stand density and stem parameters. Results and Conclusions: DBH, branch diameter and number of branches up to 6-m stem height were significantly higher in the stands with the lowest density. These stem parameters showed a relatively clear downward trend from the lowest to the highest stand densities. The main identified variables which significantly affected stem quality, were branch diameter and diameter of the thickest branch in the bottom part of the stem, at least up to 3-m stem height. For practical use, the best fitted model was estimated when stand density, DBH, and branch diameter up to 3-m height were included in a single equation. The developed model for branch diameter could be used as a forest management tool for managing stem-wood quality.

Treatment of wood with various physical and chemical factors can change the number of wood parameters, which can also lead to changes in resistance to wood-destroying fungi. This study evaluates the effects of hydrothermal treatments (additives Fe2O3 or FeCl3 with and without commercial tannins, also without additives and fresh wood) on decay and mould fungi resistance of modified wood of Scots pine (Pinus sylvestris), Norway spruce (Picea abies), Douglas fir (Pseudotsuga menziesii), walnut (Juglans regia), and Norway maple (Acer platanoides). For wood samples, the resistance against wood decay fungi Trametes versicolor (white rot) and Coniophora puteana (brown rot) and the resistance against mould fungi Aspergillus niger and Penicillium sp. were assessed. The study findings showed that wood modified with iron compounds could cause a higher resistance to wood-destroying fungi. The weight losses of the modified and control wood, caused by T. versicolor and C. puteana, differed for coniferous and deciduous: the average weight loss of treated pine, spruce, and fir wood caused by C. puteana was higher than that caused by T. versicolor, while these differences on maple and walnut wood were not significant. The wood hydrothermal treatment with Fe2Cl3 with and without tannins significantly reduced the weight loss caused by T. versicolor and C. puteana, and the treatment with Fe2O3 slightly improved the decay resistance. For the wood, hydrothermally modified with FeCl3 and FeCl3 + tannins, the mould area for both tested Aspergillus niger and Penicillium sp. was smallest for the wood of all tested tree species compared to other treatments. A different response was obtained for coniferous and deciduous tree species wood. The spruce wood, followed by fir wood, treated with FeCl3 with and without tannins, was the most resistant against the mould fungi. Relatively low resistance against the mould fungi was fixed for the maple wood treated by various iron compounds, except the treatment with Fe2O3 + tannins, which gave a very positive response against the Penicillium sp.

This study examines the performance of 11 tree taper models to predict the diameter of bark at any given height and the total stem volume of eight dominant tree species in the boreal forests of Lithuania. Here, we develop eight new models using stochastic differential equations (SDEs). The symmetrical Vasicek model and asymmetrical Gompertz model are used to describe tree taper evolution, as well as geometric-type diffusion processes. These models are compared with those traditionally used for four tree taper models by using performance statistics and residual analysis. The observed dataset consists of longitudinal measurements of 3703 trees, representing the eight dominant tree species in Lithuania (pine, spruce, oak, ash, birch, black alder, white alder, and aspen). Overall, the best goodness of fit statistics of diameter predictions produced the SDE taper models. All results have been implemented in the Maple computer algebra system using the "Statistics" and "VectorCalculus" packages.