Energy Wood Production Research Articles

Household Fuelwood Consumption and Its Implication for Carbon Dioxide Emission

This review paper aims to gather informative data on the impact of climate extremes on the physical environment, public health, and the livelihoods of people in Ethiopia. The primary sources of data for this review were peer-reviewed journal articles obtained from electronic databases such as PubMed, Central, Scopus, and Web of Science. Globally, the vast majority of households in developing countries depend on wood energy for their daily energy needs. Such consumption trends are expected to remain a common feature of traditional wood energy production and consumption, at least in the short- to medium-terms. This situation increases the demand for firewood and charcoal from the forest. The process of harvesting standing trees for charcoal and fire wood leads to forest degradation. Although woody biomass has the function of energy consumption, and as a source of income for rural villagers and urban poor dwellers practicing agriculture, wood energy generally has low priority in national policies of developing countries. However, unsustainable management and negative environmental consequences in humid and dry forests is derived from the use of fuel wood energy. Still now there is an unsystematic assessment of the economic contribution and environmental consequences of wood energy use, so its significance and consequences have been minimized. This deforestation and forest degradation contributes 1–2.4 Gt CO2e of greenhouse gases, which is 2–7% of global anthropogenic emissions, with global greenhouse gas emissions mostly CO2.

Net carbon sequestration implications of intensified timber harvest in Northeastern U.S. forests

AbstractU.S. forests, particularly in the eastern states, provide an important offset to greenhouse gas (GHG) emissions. Some have proposed that forest‐based natural climate solutions can be strengthened via a number of strategies, including increases in the production of forest biomass energy. We used output from a forest dynamics model (SORTIE‐ND) in combination with a GHG accounting tool (ForGATE) to estimate the carbon consequences of current and intensified timber harvest regimes in the Northeastern United States. We considered a range of carbon pools including forest ecosystem pools, forest product pools, and waste pools, along with different scenarios of feedstock production for biomass energy. The business‐as‐usual (BAU) scenario, which represents current harvest practices derived from the analysis of U.S. Forest Service Forest Inventory and Analysis data, sequestered more net CO2 equivalents than any of the intensified harvest and feedstock utilization scenarios over the next decade, the most important time period for combatting climate change. Increasing the intensity of timber harvest increased total emissions and reduced landscape average forest carbon stocks, resulting in reduced net carbon sequestration relative to current harvest regimes. Net carbon sequestration “parity points,” where the regional cumulative net carbon sequestration from alternate intensified harvest scenarios converge with and then exceed the BAU baseline, ranged from 12 to 40 years. A “no harvest” scenario provides an estimate of an upper bound on forest carbon sequestration in the region given the expected successional dynamics of the region's forests but ignores leakage. Regional net carbon sequestration is primarily influenced by (1) the harvest regime and amount of forest biomass removal, (2) the degree to which bioenergy displaces fossil fuel use, and (3) the proportion of biomass diverted to energy feedstocks versus wood products.

Suitability of Fast-Growing Tree Species (Salix spp., Populus spp., Alnus spp.) for the Establishment of Economic Agroforestry Zones for Biomass Energy in the Baltic Sea Region

The main goal of this review was to provide an assessment of the potential of fast-growing tree species for the suitable transformation of agroforestry areas for biomass production in the Baltic Sea region. Our interest was to highlight the research on the management process of agroforestry zones by establishing short rotation plantations with the tree species Salix spp., Populus spp. and Alnus spp. to explore the prospects of planning these zones as biomass producers. Short rotation forestry (SRF) with trees whose rotation period is 15 to 30 years, depending on the species, is the most suitable approach for management of these agroforestry zones. Willows (Salix spp.) and poplars (Populus spp.) are suitable for short rotation coppice (SRC), as these tree species can be harvested at much shorter intervals, respectively, 1–5 and 4–10 years, facilitating their use in agricultural systems. The rotation period of Alnus spp. in short rotation plantations for energy wood production is generally assessed to be 15–30 years. The black alder plantations in agroforestry zones are used for sawnwood and firewood production, with a rotation period of 20–40 years. The calculated repayment period of the economic agroforestry zone is about 10–15 years, if 2021 costs and prices are used.

Growth, Productivity, Biomass and Carbon Stock in Eucalyptus saligna and Grevillea robusta Plantations in North Kivu, Democratic Republic of the Congo

Initiated by the World Wildlife Fund (WWF) more than a decade ago in North Kivu, single-species plantations of Eucalyptus saligna and Grevillea robusta constitute, with other village plantations, the current legal source of wood-energy for the communities bordering the Virunga National Park (PNVi). This study assesses the growth and productivity of these plantations in two sites with different soil and climatic conditions to predict their production over time. The study also assesses the carbon stock and long-term CO2 fixation in the biomass of the studied plantations to deduce their contribution to climate change mitigation. Non-destructive inventories were carried out during three consecutive years in 20 E. saligna and 12 G. robusta plantations in Sake and Kirumba. Analysis of the data revealed that both species have similar diametric growth while height growth and productivity were significantly higher in the E. saligna plantations. The productivity of E. saligna was also higher in Kirumba than in Sake, while that of G. robusta was higher in Sake than in Kirumba. The differences observed were mainly related to species, silviculture, altitude and concentration of bioavailable elements in the soils. The analysis of productivity evolution over time allowed us to determine optimal rotations at 8 and 12 years, respectively, for E. saligna and G. robusta plantations. The relationships between biomass or carbon stock and tree diameter were not different between the studied species but were significantly different at the stand level. If silviculture was standardized and plantations carefully monitored, carbon stock and long-term CO2 fixation would be higher in G. robusta plantations than in E. saligna plantations. These results indicate that while for productivity reasons E. saligna is the favoured species in wood-energy plantations to quickly meet the demand of the growing and disadvantaged population living in the vicinity of PNVi, carefully monitored G. robusta plantations could be more interesting in terms of carbon credits. To simultaneously optimise wood-energy production and carbon storage in the plantations initiated in North Kivu, E. saligna and G. robusta should be planted in mixture. In addition, species and site characteristics adapted silvicultural management practices must be applied to these plantations, which are very important for the region, its population and its park. Finally, the economic profitability as well as the sustainability of the plantations should be assessed in the longer term in North Kivu.

Genetic parameters of growth and biomass in <i>Leucaena leucocephala</i> for wood energy

Leucaena leucocephala is a potential species for wood-energy production in Indonesia. A study of genetic improvement was initiated with a progeny test of 80 lines from 10 seed sources. Plant height and stem diameter were measured at 6 and 18 months, growth index (GI) calculated at 18 months and wood biomass production measured at 30 months. Differences between seed sources for height and diameter were observed at 6 months but not at 18 months. Significant differences between lines within seed source were observed for height and diameter at 6 months and these differences remained at 18 months. Differences between lines for GI and biomass were significant at 18 and 30 months respectively. At 18 months, line mean heritability for height, diameter and GI were estimated to be moderate, namely 0.62, 0.61 and 0.62 respectively. At 30 months line mean heritability for biomass was moderately low (0.39). Genetic correlations between height and diameter were moderately high at 6 months (0.74) and increased at 18 months (0.82), while correlation between diameters at 6 and 18 months was high (0.93). The expected genetic gain from selecting the 25 and 10 best lines with a high line value for GI was 33.7% and 48.8% respectively, with lines from the Indonesian local seed sources found to be the best performers. Three lines from the newly introduced Tarramba cultivar also had good performance. These results are discussed in relation to the future improvement program of this species for wood energy production.

Households and tree-planting for wood energy production – Do perceptions matter?

While forests are a primary source of energy for the majority of Tanzanian households, the forest cover is rapidly declining. The Tanzanian government has introduced a tree-planting campaign strategy, aimed at reducing pressure on natural forests. However, the campaign appears not to have contributed significantly to the forest recovery rate. Thus, this study aims at examining household perceptions of tree-planting for wood energy production for both in-house uses and for sale, and identify the factors influencing household perceptions of tree-planting. We employed the multinomial logit model to analyse the factors influencing household perceptions of tree-planting for energy. Our findings indicate that respondents considered the right/freedom to harvest trees from farms and transport them to markets as the most important factor (86%), followed by lack of awareness of tree-planting programmes (72%), and the existence of fuelwood for free from natural forests (59%). The size of the farm, education, distance to forest reserves, and age of the household head are found to have significant impact on the household perceptions of tree-planting for energy. Our results further show that woodfuel harvesting and enforcement systems do not exist in nearby forests. This situation is exacerbated by the absence of a specific policy formulated to match with the daily demand of forest produce for energy and income of households near forest reserves. Thus, we suggest policy makers to target policies and actions promoting tree-planting for energy.

Bridging mapping and simulation modelling in the ecosystem service assessments of boreal forests: effects of bioenergy production on carbon dynamics

BackgroundIncreasing the use of forest harvest residues for bioenergy production reduces greenhouse emissions from the use of fossil fuels. However, it may also reduce carbon stocks and habitats for deadwood dependent species. Consequently, simple tools for assessing the trade-offs of alternative management practices on forest dynamics and their services to people are needed. The objectives of this study were to combine mapping and simulation modelling to investigate the effects of forest management on ecosystem services related to carbon cycle in the case of bioenergy production; and to evaluate the suitability of this approach for assessing ecosystem services at the landscape level. Stand level simulations of forest growth and carbon budget were combined with extensive multi-source forest inventory data across a southern boreal landscape in Finland. Stochastic changes in the stand age class distribution over the study region were simulated to mimic variation in management regimes.ResultsThe mapping framework produced reasonable estimates of the effects of forest management on a set of key ecosystem service indicators: the annual carbon stocks and fluxes of forest biomass and soil, timber and energy-wood production and the coarse woody litter production over a simulation period 2012–2100. Regular harvesting, affecting the stand age class distribution, was a key driver of the carbon stock changes at a landscape level. Extracting forest harvest residues in the final felling caused carbon loss from litter and soil, particularly with combined aboveground residue and stump harvesting. It also reduced the annual coarse woody litter production, demonstrating negative impacts on deadwood abundance and, consequently, forest biodiversity.ConclusionsThe refined mapping framework was suitable for assessing ecosystem services at the landscape level. The procedure contributes to bridging the gap between ecosystem service mapping and detailed simulation modelling in boreal forests. It allows for visualizing ecosystem services as fine resolution maps to support sustainable land use planning. In the future, more detailed models and a wider variety of ecosystem service indicators could be added to develop the method.

Decision support system for energy wood production

An approach to the application of modern information technologies and mathematical methods to solve the problem of energy woodproduction and logistics technologies selection is described in the article. The general statement of the problem, the methodology, methodsand models used are given.A decision support system for energy wood production can evaluate and compare various technological schemes for the harvesting and processing of woody biomass to energy woodand identify the most effective choice At the operational level, the approach allows to optimize the current plans for the harvesting, initial processing and transportation of the energy wood for available production capacities, taking into account the commercial roundwood production providing at the same time. Proposed approach isa practical tool for ensuring profitability and sustainable growth of the energy wood production, which, will stimulate the development of bioenergy in Russia.

К вопросу производства энергетическодисковыми рубительными машинами с различными способами выброса щепы

К вопросу производства энергетическодисковыми рубительными машинами с различными способами выброса щепы

Trade-Off between Energy Wood and Grain Production in Temperate Alley-Cropping Systems: An Empirical and Simulation-Based Derivation of Land Equivalent Ratio

The alley-cropping systems (ACSs), which integrate parallel tree strips at varying distances on an agricultural field can result, complementarity of resource use, in an increased land-use efficiency. Practitioners’ concerns have been directed towards the productivity of such systems given a reduced area covered by agricultural crops. The land equivalent ratio (LER) serves as a valuable productivity indicator of yield performance and land-use efficiency in ACSs, as it compares the yields achieved in monocultures to those from ACSs. Consequently, the objective of this combined experimental and simulation study was to assess the tree- and crop-yields and to derive the LER and gross energy yield for two temperate ACSs in Germany under different design scenarios, i.e., tree arrangements (lee- or wind-ward) and ratios of tree area to crop area. Both LER and gross energy yields resulted in a convex curve where the maximum values were achieved when either the tree or crop component was dominant (>75% of the land area) and minimum when these components shared similar proportions of land area. The implications of several design scenarios have been discussed in order to improve the decision-making, optimization, and adaptation of the design of ACSs with respect to site-specific characteristics.

Northern mixedwood composition and productivity 50 years after whole-tree and stem-only harvesting with and without post-harvest prescribed burning

Whole-tree harvesting (WTH) is increasingly used to extract forest biomass for energy and commercial wood products. Slash burning, which is used for fuels reduction and site preparation, also reduces aboveground biomass. Yet effects of incremental biomass reduction, from either WTH or slash burning, on long-term forest productivity and composition are poorly understood. This research uses data from a 50-year-old study in northern mixedwood (Picea – Abies – hardwood) stands on the Penobscot Experimental Forest in Maine, U.S.A., to address these concerns. Clearcutting was conducted in 1964–65 with WTH, stem-only harvesting (SOH), and SOH with post-harvest prescribed burning of logging residues (SOHB). Growing stock, composition, and soil properties (O horizon thickness and soil drainage) were measured 50 years after treatment. Hardwood composition (percent of total basal area) increased from pre-treatment levels in all treatments but was greater in SOHB than SOH and WTH. Eastern white pine (Pinus strobus), though a minor species, was significantly more abundant in WTH than SOH or SOHB. Results indicated no other significant differences in species composition, or in stand structure or productivity (total basal area, stem density, dominant height, quadratic mean diameter, and total above-ground carbon stock) among treatments. Independent of treatment, we observed relationships between soil properties and stem density and quadratic mean diameter (qmd), such that lower stem density and greater qmd were observed on sites with greater O horizon thickness. These findings suggest that relative to SOH, WTH and SOHB do not degrade northern mixedwood stand productivity as expressed by stand structure and stocking 50 years after a single treatment, even on a site with low to moderate production potential. Nevertheless, species shifts associated with clearcutting (i.e., shade-tolerant conifer to intolerant hardwood composition) and prescribed burning in this forest type should be considered in light of the potential application of either for intensive silviculture treatments.

Long term impact of Acacia auriculiformis woodlots growing in rotation with cassava and maize on the carbon and nutrient contents of savannah sandy soils in the humid tropics (Democratic Republic of Congo)

Rotational woodlots with N2-fixing trees may be efficient agroforestry systems, allowing farmers to alternate agricultural and wood-energy production on the same area. However, their long-term effect on soil fertility is poorly understood. The aim of this study was to investigate the influence of successive phases of Acacia auriculiformis stands growing in rotation with crops on the chemical properties of sandy and very poor tropical soils. The study was conducted 22 years after the afforestation of humid herbaceous savannah in Mampu, Democratic Republic of Congo. The chemical properties of top soil (0–20 cm) from control savannah plots were compared with those from acacia plots that had undergone one, two or three rotations of acacia during the 22 year period. We found that the soil properties under non-harvested acacia stands in a 1st rotation and under acacia stands in a 2nd or 3rd rotation following charcoal production and maize and cassava cultivation were similar. Soils under all acacia stands had higher C, N and $${\text{NO}}_{3}^{ - }$$ –N contents, but were more acidic, and had lower contents of exchangeable Ca, Mg, K and Na than the control savannah soils. Despite the increase in soil C and N, the sustainability of the acacia rotational agroforestry system after 22 years of practice is in question due to the steady decrease of soil cations, soil acidification and the risk of a decline in tree and crop productivity. To improve the nutrient balance and the sustainability of this system, different practices are recommended such as the debarking of tree stems before carbonization, the restitution of small branches and charcoal residues to the soil, and the supply of natural rock phosphate.

Croatian and Serbian private forest owners’ perceptions of energy wood mobilization: survey results and relevance for future bioeconomy

ABSTRACTIn recent years, new policies have emerged in Europe related to both bioenergy and bioeconomy. The study investigated perceptions of the Croatian and Serbian non-industrial private forest owners (NIPFs) concerning energy wood mobilization from forests owned by them. A total of 232 NIPFs from the two countries participated in the study. The NIPFs perceived that they did not have adequate knowledge of selling energy wood, its price, and energy wood entrepreneurship. According to the NIPFs, the most significant obstacle to mobilizing energy wood from private forests was the lack of proper forest roads in their countries. Among the economic instruments, the NIPFs favored subsidies and guaranteed market over tax reduction for mobilizing energy wood and establishing energy wood entrepreneurship. Their main motivation for energy wood production appeared to be expected income from such an activity. It also appeared that the NIPFs would prefer supplying energy biomass from new plantations and harvesting residues instead of using their existing forests. The study provided a number of recommendations for the policy makers in Croatia and Serbia on improving the preconditions for energy wood mobilization from private forests and linking it with the bioeconomy by addressing the issues related to policy, infrastructure, and market development.

The impact of short-rotation hybrid aspen (Populus tremula L. × P. tremuloides Michx.) plantations on nutritional status of former arable soils

The area of short-rotation forest (SRF) plantations with hybrid aspen (Populus tremula L.×P. tremuloides Michx.) for pulp and energy wood production in approximately 25-year rotation period has increased considerably during the last few decades in Northern Europe on previous agricultural lands. However, little is known about how this new land use will alter the chemical properties of soils in the long-term and how long nutrients from the land’s previous use will sustain high productivity of trees. Little is also known about the dynamics of soil micronutrients and the plantations’ influence on subsoil layers. Repeated soil monitoring was carried out in hybrid aspen plantations at the ages of 5 (young) and 15years (midterm) to detect changes in soil chemical characteristics, including soil reaction (pHKCl), and concentrations of nutrients and organic carbon (Corg) in A- and B-horizon on 51 permanent experimental plots. The main soil- and stand-related factors responsible for changes in soil chemical properties, were analyzed. Significant changes were observed both in soil A-horizon and B-horizon. In A-horizon, pHKCl (−0.2 units), Ca (−19.4%) and B (−25.8%) had decreased while total N (+5.8%), Cu (+20.3%) and Mn (+21.3%) had increased. In B-horizon, Ca (−23.4%), Mg (−12.8%) and B (−45.0%) had decreased, while Corg (+17.2%) and Cu (+53.8%) had increased. The concentrations of available P, K and Corg in A-horizon had remained unchanged. Reduction of soil chemical characteristics mainly occurred in plantations where their initial level had been high (this relationship was observed in A-horizon for total N and B and in B-horizon for Corg, Mg and B). Several soil chemical characteristics decreased more (or increased less) in plantations where tree growth was more vigorous (in A-horizon: pHKCl, total N and B; in B-horizon: Mg and B). Soil cation exchange capacity, base saturation and moisture conditions also explained some of the observed variation in changes. Relatively high loss of B in faster growing plantations indicates possible future limitations of this essential micronutrient. To summarize, first generation hybrid aspen plantations planted on former agricultural fields had significantly altered soil reaction (pHKCl) but did not show significant depletion of primary macronutrients (N, P, K) and soil organic carbon.

Sustainability Frames in the Context of the Energy Wood Conflict in Germany

Interpretations of the concept of sustainability vary substantially in relation to forests and their management, and they are usually present in conflicts about forest use. In this article, we consider underlying interests relating to conflicts of forest use as a given. Our aim is therefore not to reveal those interests, but rather to explore understandings of sustainability hiding behind them—sustainability frames. To this end, we use frame theory to investigate the following research question: How are different sustainability frames of interest groups reflected in a forest use conflict situation in Germany? The energy wood conflict serves as the example for our research, as it is currently the most prominent forest management conflict in Germany. Using 12 stakeholder interviews within three interest groups as the empirical data basis, it becomes clear that sustainability understandings reflect particular positionings in conflicts, or vice versa. In the energy wood conflict, the classic dichotomy between forestry and conservation groups becomes a trichotomy in which the forestry group splits into an interest group that profits from energy wood production and one that competes with it. We suggest that sustainability understandings do not represent worldviews that guide how actors understand conflicts, but rather that they are shaped according to actors’ particular interests in conflicts.

Willingness of Nonindustrial Private Forest Owners in Norway to Supply Logging Residues for Wood Energy

Norway has set ambitious targets for increasing bioenergy production. Forest residue extraction levels are currently very low, but residues have the potential to be an important component of the wood energy supply chain. A representative sample of Norwegian nonindustrial private forest owners having at least 8 ha (20 acres) of productive forest land was surveyed about their willingness to supply logging residues for wood energy production. About 59 % responded that they were willing to do so. Logistic regression analyses revealed that the following factors were positively associated with the likelihood of being willing to supply logging residues: total forest area, education level, living in a region with active timber markets and a history of forest production, and having positive perceptions of residue extraction and forestry’s role in mitigating climate change. Four variables were negatively associated with the likelihood to supply residues: living on property, being older than 65 years, having family or friends who are opposed to residue extraction, and having negative perceptions of residue extraction. The study provides insight regarding nonindustrial forest owners’ attitudes towards extraction of forest residues that may aid policy-makers designing effective means to meet national bioenergy production goals.

The socioeconomic and environmental impacts of wood energy value chains in Sub-Saharan Africa: a systematic map protocol

Abstract Background The vast majority of households in Sub-Saharan Africa (SSA) depend on wood energy—comprising firewood and charcoal—for their daily energetic needs. Such consumption trends are expected to remain a common feature of SSA’s wood energy production and supply chains, at least in the short- to medium-terms. Notwithstanding its importance, wood energy generally has low priority in SSA national policies. However, the use of wood energy is often considered a key driver of unsustainable management and negative environmental consequences in the humid and dry forests. To date, unsystematic assessments of the socio-economic and environmental consequences of wood energy use have underplayed its significance, thus further hampering policy debates. Therefore, a more balanced approach which considers both demand and supply dynamics is needed. This systematic map aims at providing a comprehensive approach to understanding the role and impacts of wood energy across all regions and aspects in SSA. Methods The objective of this systematic map is to collate evidence from studies of environmental and socio-economic impacts of wood energy value chains, by considering both demand and supply within SSA. The map questions are framed using a Populations, Exposure, Comparators and Outcomes (PECO) approach. We name the supply and demand of wood energy as the “exposure,” composed of wood energy production, harvesting, processing, and consumption. The populations of interest include both the actors involved in these activities and the forest sites where these activities occur. The comparator is defined as those cases where the same wood energy activities occur with i) available/accessible alternative energy sources, ii) regulatory frameworks that govern the sector and iii) alternative technologies for efficient use. The outcomes of interest encompass both socioeconomic and environmental impacts that can affect more than the populations named above. For instance, in addition to the direct socioeconomic impacts felt by participants in the wood energy value chain, forest dwellers may experience livelihood changes due to forest degradation caused by external harvesters. Moreover, intensified deforestation in one area may concurrently lead to forest regeneration in another.

Energy wood from forests—stakeholder perceptions in five European countries

In the last decade, the demand for and supply of energy wood from forests has increased, and experts expect a further increase in the future due to political and societal changes. The objective of this paper was to provide a qualitative analysis of stakeholders’ perceptions of current and future trade-offs as well as of synergies between energy wood production and use and other forest ecosystem services (ES). We developed an explorative research approach and conducted semi-structured interviews with a total of 103 interviewees of six selected stakeholder groups in five European countries: Finland, Germany, Norway, Slovenia and Spain. For the analysis, we adopted a qualitative content analysis approach. The results of this empirical study indicate that, across the five countries, stakeholders perceive similar trade-offs and synergies. Stakeholders perceive a strong synergy with employment whereas trade-offs regarding conservation of biodiversity are the most critical issue related to energy wood production in forests. Furthermore, stakeholders continue the classic debate about forest protection versus forest use in the energy wood context. Effects of energy wood production and use need to be taken into account in policy development and forest management in order to address current and future trade-offs and to tap the full potential of synergies related to other forest ES. Different characteristics of countries and regions need to be considered, and decisions need to be fostered by long-term and far-reaching political frameworks.

Effects of Energy Wood Harvesting on Timber Production Potential and Biological Diversity in North Karelia, Finland

We conducted a two-dimensional production possibility frontier analysis to study the relationships between energy wood removal and 10 variables representing timber production possibilities and biological diversity. The analysis was restricted to the North Karelia region in Eastern Finland over a 40-year period. A large-scale forest planning system was used to define efficient future joint production possibilities between energy wood removal and the 10 variables. The results indicate that in North Karelia, a moderate amount of forest chips and firewood can be harvested without large impacts on the timber production potential or biological diversity. Large amounts of energy wood can be harvested from thinning stands, and this simultaneously supports timber production. Energy wood can be harvested from young stands with only minor effects on variables measuring biological diversity. However, if the economic outcome is maximized, about 50% of the energy wood removal at the target level of 1.5 million m3 year−1 will be from final cutting areas. The results of this analysis show that economically sound production of energy wood is strongly linked to the harvesting operations of other forest industries.

Corrigendum to “Energy wood production from private forests – Nonindustrial private forest owners׳ perceptions and attitudes in Croatia and Serbia” [Renew. Sustain. Energy Rev. 35 (2014) 515–526

Corrigendum to “Energy wood production from private forests – Nonindustrial private forest owners׳ perceptions and attitudes in Croatia and Serbia” [Renew. Sustain. Energy Rev. 35 (2014) 515–526