Forests — Open Access Journal of Forestry

A positive nutrient balance is crucial to sustaining forest productivity. Differences in stand densities usually mean different aboveground biomass stocks and different proportions of tree compartments. These differences can be reflected in the different macronutrient stocks between stands of different densities, because various tree compartments have different element concentrations. In this study, 82-year-old stands of Scots pine were compared, and specifically, the concentrations of the elements in tree compartments and the amounts of macronutrients in aboveground biomass were compared. The nutrients considered in this study were nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur. A positive correlation between stand density and the level of stored macronutrients was found for nitrogen, phosphorus, and potassium. This result means that forest managers can influence nutrient balances by regulating stand densities or by harvesting methods (SOH: stem-only harvesting or WTH: whole-tree harvesting). Full article

We simulated Austrian forests under different sustainable management scenarios. A reference scenario was compared to scenarios focusing on the provision of bioenergy, enhancing the delivery of wood products, and reduced harvesting rates. The standing stock of the stem biomass, carbon in stems, and the soil carbon pool were calculated for the period 2010–2100. We used the forest growth model Câldis and the soil carbon model Yasso07. The wood demand of all scenarios could be satisfied within the simulation period. The reference scenario led to a small decrease of the stem biomass. Scenarios aiming at a supply of more timber decreased the standing stock to a greater extent. Emphasizing the production of bioenergy was successful for several decades but ultimately exhausted the available resources for fuel wood. Lower harvesting rates reduced the standing stock of coniferous and increased the standing stock of deciduous forests. The soil carbon pool was marginally changed by different management strategies. We conclude that the production of long-living wood products is the preferred implementation of climate-smart forestry. The accumulation of carbon in the standing biomass is risky in the case of disturbances. The production of bioenergy is suitable as a byproduct of high value forest products. Full article

An effective way to reduce off-road traffic in forests is to implement greater distances between skid trails. However, this implies that trees beyond the boom reach of the harvester need to be felled motor manually before being winched to the skid trail, for example using a remote-controlled mini forestry crawler (MFC). They are only a few local studies which have evaluated the performance of such MFCs. The use of MFCs for wood extraction operations in mixed soft- and hardwood stands is presented in this study conducted in Southwestern Germany. The aim of this study was to analyze the productivity, costs, and selected environmental impacts of mini forestry crawlers during winching operations through a time study. Using statistical regression, time consumption was analyzed in order to determine significant explanatory variables. Environmental impacts were evaluated using the life cycle assessment (LCA) methodology with Umberto software. The mean net cycle time was 4.82 min and the net productivity rate was 7.77 m³ by productive machine hour (PMH₀). Explanatory variables which significantly affected the net cycle time were the winched volume, the number of trees per load, and winching distance. Environmental analysis showed that inputs of fossil energy were mostly due to diesel and lubricant consumption. Raw materials for machine manufacture and maintenance showed the highest impact in human toxicity potential category. The MFCs showed good environmental performances, but the harvesting system should become more productive in order to be more cost effective. Full article

Despite strong expectations regarding the role that forestry, with its multitude of potential benefits, could and should play in the ‘bio-economy’, little research has been done on the actual perceptions of influential actors on how to best address future forest land-use disputes. We want to shed light on whether and in which contexts expectations regarding the bio-economy, e.g., the strong role of markets, are likely. The paper analyses influential actors’ core values and beliefs about the primary facilitators and the most appropriate instruments for resolving disputes over future forest land use. We used Social Network Analysis-based sampling and a quantitative semi-structured questionnaire, which included a preference analysis with twelve items covering broad issues and disputes related to future forest land use, to identify actors’ beliefs about and preferences for facilitators and policy instruments within key issues for future land use. The respondents were asked to identify one of five ‘primary facilitators’ (state, market, society, individual citizens/owners, leave it to nature) and distribute six points to a maximum of three preferred instruments (eight items, covering a broad set of instruments, from dictates or bans to awareness raising). The results are based on the perceptions of the influential or most important actors from various innovative government and private forest initiatives in Bavaria (Germany), Slovenia, Castilla y León (Spain), Nordeste (Portugal), and Latvia (481 actor responses, 109 initiatives). The initiatives included participatory mountain forest initiatives, forest intervention zones, afforestation projects, forest owner associations, and model forest and labelling initiatives. The results provide insight into the similarities and differences between European countries and actor groups regarding the preferred facilitators and instruments for solving future forest problems. In light of disagreement in the literature on the role of the state or markets in future forest land use and the bio-economy, our results show that the market and its instruments are considered to play a dominant role in wood mobilisation. With respect to all other issues (socio-ecological, societal, other), the state or other institutions and their instruments gain priority. The state is considered to play a stronger role in developing new markets, e.g., for energy transition or new uses of wood, contrary to liberal market expectations. Ecological and social problems are considered to be outside of the market domain. Here, the state is called in, e.g., to steer recreational issues, the provision of ecosystem services, or the improvement of the protective function. The clearest preference across all regions is for the state to secure the provision of ecosystem services, in contrast to calls for future markets to regulate this field. Full article

Almost a decade since the establishment of Reducing Emissions from Deforestation and Degradation (REDD+), this study investigates the extent to which REDD+ projects are delivering on the promise of co-benefits and the elusive ‘triple-win’ for climate, biodiversity, and local communities. The Climate, Community and Biodiversity Alliance (CCB) is among several leading REDD+ certification standards that are designed to support the delivery of social and environmental co-benefits, and ‘socially-just’ carbon. This study uses an in-depth content analysis of 25 subnational REDD+ project documents to assess the extent to which REDD+ project objectives align with Sustainable Development Goals (SDG) targets, and evaluates the reporting of progress towards meeting these objectives. Currently the CCB standards address a relatively small subset of SDG targets. Despite this, we find that REDD+ projects aspire to work on a much broader set of SDG target objectives, thus going beyond what the CCB Standards require for REDD+ validation. However, although reviewed REDD+ projects have these aspirations, very few are actively monitoring impact against the goals. There is a gap between aspiration and reported progress at the goal level, and for each project: on average, only a third of SDGs that are being targeted by REDD+ projects are showing ‘improvement’. The analysis shows which global goals are most frequently targeted, and which are the least. It also allows an analysis of which projects are following through most effectively in terms of monitoring progress towards the SDGs. This assessment provides insights into the priorities of REDD+ project proponents, suggesting that REDD+ has unfulfilled potential to elicit positive change in relation to the SDGs. Our analysis also shows that there is considerable potential for the safeguarding bodies to do more to ensure that real improvements are made, and reported against, aligning REDD+ projects more strongly with global development agendas. Full article

Many northern hardwood stands include several low-vigor trees as a result of past management. To restore these degraded stands, partial cuts are applied with partly validated tree classification systems that are based upon apparent stem defects. We sampled 214 sugar maple (Acer saccharum Marsh.) and 84 yellow birch (Betula alleghaniensis Britt.) trees from six sites covering the northern hardwood forest zone of the Province of Quebec, Canada. We evaluated their vigor with a four-class system, and quantified the growth efficiency index and several indices that were based solely upon radial growth. The growth efficiency index increased non-significantly with increasing tree vigor class. The five-year basal area increment (BAI_-1-5) was significantly different between the lowest and highest tree vigor classes. Yet, temporal changes in BAI_-1-5 helped classify correctly only 16% of high-vigor trees that became poorly vigorous 8–10 years later. Overall, these results suggest that the tree classification system is weakly related to actual tree vigor and its application likely generates few significant gains in future stand vigor. Modifying and simplifying the tree vigor system must be considered to facilitate the tree marking process that is required to improve the vigor of degraded stands. Full article

Carbon pool assessments in forests is one of the most important tasks of forest ecology. Despite the wide cultivation range, and economical and traditional importance, the aboveground biomass of European larch (Larix decidua Mill.) stands is poorly characterized. To increase knowledge about forest biomass accumulation and to provide a set of tools for aboveground biomass estimation, we studied a chronosequence of 12 larch forest stands (7–120 years old). From these stands, we measured the biomass of 96 sample trees ranging from 1.9 to 57.9 cm in diameter at breast height. We provided age-specific and generalized allometric equations, biomass conversion and expansion factors (BCEFs) and biomass models based on forest stand characteristics. Aboveground biomass of stands ranged from 4.46 (7-year-old forest stand) to 445.76 Mg ha⁻¹ (106-year-old). Stand biomass increased with increasing stand age, basal area, mean diameter, height and total stem volume and decreased with increasing density. BCEFs of the aboveground biomass and stem were almost constant (mean BCEFs of 0.4688 and 0.3833 Mg m⁻³, respectively). Our generalized models at the tree and stand level had lower bias in predicting the biomass of the forest stands studied, than other published models. The set of tools provided fills the gap in biomass estimation caused by the low number of studies on larch biomass, which allows for better estimation of forest carbon pools. Full article

A variety of commercial instruments are available for sampling and quantifying microscopic airborne organisms from the environment. Although most samplers are highly sensitive, they are also expensive, costing thousands of dollars per unit, a price that is out of reach for many researchers, especially those looking to design experiments with replication. While looking at options to monitor pine stands for the presence of Fusarium circinatum, the causal agent of pitch canker disease, on multiple sites with several units per site, we developed a simple, low-cost spore trap that allows surveying spore abundance in outdoor environments. The trap consists of a rotating motor that holds a metal rod and two petroleum jelly-coated microscope slides. As the motor rotates, the slides collect airborne particles. To test whether the traps allowed detection of F. circinatum spores, we placed six traps on three sites: an actively-managed slash pine commercial stand located in Lake Butler, FL, a semi-managed loblolly and slash pine stand near Gainesville, FL, and a site with little perturbance at Goethe State Forest, FL, consisting of mainly slash pine trees. The slides were replaced weekly, and F. circinatum was detected by quantitative PCR using species-specific primers. Results show detection of low levels ($\overline{\mathrm{X}}$ = 1.7–77.1 picograms ± SE = 0.3–39.7) of the pathogen spores with high reproducibility. These traps offer a low-cost solution to spore, pollen, or small insect trapping experiments for initial or general assessment of a pathogen or species population. Their low cost has the added benefit that multiple traps can be deployed per experiment, thus increasing statistical power by using multiple replications. Full article

Internationally forest biomass is considered to be a valuable renewable energy feedstock. However, utilization of forest harvesting residues is challenging because they are highly varied, generally of low quality and usually widely distributed across timber harvesting sites. Factors related to the collection, processing and transport impose constraints on the economic viability of residue utilization operations and impact their supply from dispersed feedstock locations. To optimize decision-making about suitable locations for biomass energy plants intending to use forest residues, it is essential to factor in these supply chain considerations. This study conducted in Tasmania, Australia presents an investigation into the integration of Multi-criteria analysis (MCA) and Geographical Information systems (GIS) to identify optimal locations for prospective biomass power plants. The amount of forest harvesting biomass residues was estimated based on a non-industrial private native resource model in Tasmania (NIPNF). The integration of MCA and a GIS model, including a supply chain cost analysis, allowed the identification and analysis of optimal candidate locations that balanced economic, environmental, and social criteria within the biomass supply. The study results confirm that resource availability, land use and supply chain cost data can be integrated and mapped using GIS to facilitate the determination of different sustainable criteria weightings, and to ultimately generate optimal candidate locations for biomass energy plants. It is anticipated that this paper will make a contribution to current scientific knowledge by presenting innovative approaches for the sustainable utilization of forest harvest residues as a resource for the generation of bioenergy in Tasmania. Full article

Close-to-nature urban forests and remnants of natural vegetation represent an important opportunity for urban residents to experience daily perception of and access to the natural environment. Despite there being a high percentage of forest cover (59%) and a favorable structure of the prevailing forested landscapes in Slovenia, urban expansion and infrastructure-driven development has severely weakened the connectivity and conservation of urban and suburban forests. The majority of urban settlements lie within walking distance of the surrounding forests (<1 km). However, only close-to-nature forests with relatively low silvicultural inputs offer ecosystem services sufficient to fulfil the supply and demand of the expanding urban population. In order to estimate the conservation of forests in the open space of Slovenian settlements, we used a spatial model of landscape structure and forest connectivity. The model can be enhanced with patterns of corridors and stepping stones of natural vegetation in the landscape matrix to provide support in the decision-making process of landscape planning and the conservation of urban and suburban forests. Full article

Optimal planning of the amount and type of resources needed for extinguishing a forest fire is a task that has been addressed in the literature, using models obtained from operational research. In this study, a general integer linear programming model is proposed, which addresses the allocation of resources in different time periods during the planning period for extinguishing a fire, and with the goal of meeting Spanish regulations for the non-negligence of fronts and periods of rest for pilots and brigades. A computer program and interface were developed using the R language. By means of an example using historical data, we illustrate the model at work and its exact resolution. Then, we carry out a simulation study to analyze the obtained objective functions and resolution times. Our simulation study shows that an exact solution can be obtained very quickly without requiring heuristic algorithms, provided that the planning period does not exceed five hours. Full article

Accurate forest above-ground biomass (AGB) is crucial for sustaining forest management and mitigating climate change to support REDD+ (reducing emissions from deforestation and forest degradation, plus the sustainable management of forests, and the conservation and enhancement of forest carbon stocks) processes. Recently launched Sentinel imagery offers a new opportunity for forest AGB mapping and monitoring. In this study, texture characteristics and backscatter coefficients of Sentinel-1, in addition to multispectral bands, vegetation indices, and biophysical variables of Sentinal-2, based on 56 measured AGB samples in the center of the Changbai Mountains, China, were used to develop biomass prediction models through geographically weighted regression (GWR) and machine learning (ML) algorithms, such as the artificial neural network (ANN), support vector machine for regression (SVR), and random forest (RF). The results showed that texture characteristics and vegetation biophysical variables were the most important predictors. SVR was the best method for predicting and mapping the patterns of AGB in the study site with limited samples, whose mean error, mean absolute error, root mean square error, and correlation coefficient were 4 × 10⁻³, 0.07, 0.08 Mg·ha⁻¹, and 1, respectively. Predicted values of AGB from four models ranged from 11.80 to 324.12 Mg·ha⁻¹, and those for broadleaved deciduous forests were the most accurate, while those for AGB above 160 Mg·ha⁻¹ were the least accurate. The study demonstrated encouraging results in forest AGB mapping of the normal vegetated area using the freely accessible and high-resolution Sentinel imagery, based on ML techniques. Full article

Allometric equations are useful tools for calculating tree and stand-level attributes, such as above-ground biomass or stem volume, using simple measurements that can be obtained from stand inventory data. These equations tend to be species-specific and can be affected by site conditions and silvicultural treatments. Forest vegetation management treatments (VM) are an important component of reforestation programs in the Pacific Northwest of the United States; however, no study has investigated the impact of these treatments on crop tree allometry. In this study we assessed the long-term effects of two contrasting VM treatments on the allometry of sixteen-year-old Douglas-fir, western hemlock, western redcedar, and grand fir trees growing in Oregon’s central Coast Range (CR) and fifteen-year-old Douglas-fir and western redcedar trees growing in Oregon’s Cascade foothills (CF). The VM treatments included a control which received only a pre-planting herbicide application and a VM treatment consisting of five consecutive years of vegetation control after planting. The equations developed in this study were species-specific and were not affected by VM with the exception of western redcedar foliage biomass. For western redcedar, tress of similar diameter had more foliage biomass when growing on plots without VM after planting. The allometry of Douglas-fir and western redcedar was also found to be affected by site, such that trees of similar diameter and height had larger stem volume when growing at the CR site than the CF site. This difference in stem volume was found to be the result of differences in stem tapering. There was a strong relationship between stand basal area and leaf area index that was the same for all species tested and was unaffected by site. The equations presented in this study are useful for calculating stem volume, leaf area and individual tree and component biomass for stands of the studied species that are of similar age. Full article

The multiple agroforestry land uses of oak forests are of great ecological and economic interest as they contribute to the improvement of animal husbandry, wildlife, and environment. However, herbivory by wildlife and livestock highly affects the structure and the dynamic of forest ecosystems including its regeneration. The aim of this study was to investigate the comparative effect of wild boar and small ruminants herbivory on the regeneration of a deciduous oak forest in northern Greece. Eight sites were selected in an even aged stand of similar canopy cover and forest site quality: four sites with long-time use mainly by wild boar and four sites with long-time grazing by sheep and browsing by goats. A plot of 150 m² in each of the sites was fenced in order to be protected from herbivory. The plant cover and number of oak seedlings and acorns was measured in both grazed and protected plots for four consecutive years. The plant cover increased in the protected plots independent of the type of animals. The seedling cover decreased about 29% and 9% in sites where small ruminants and wild boars foraged respectively. Similarly, the number and the weight of acorns significantly decreased in the sites grazed by small ruminants mainly during the mast year of the oaks. Forest management has to control the small ruminants grazing in terms of intensity, timing, and duration in order to ensure the sustainability of the ecosystem. Full article

The classification of discrete forest disturbance events is usually based on the spatial extent, magnitude, and frequency of the disturbance. Based on these characteristics, disturbances are placed into one of three broad categories, gap-scale, intermediate-severity, or catastrophic disturbance, along the disturbance classification gradient. We contend that our understanding of disturbance processes near the endpoints of the disturbance classification gradient far exceeds that of intermediate-severity events. We hypothesize that intermediate-severity disturbances are more common, and that they are more important drivers of forest ecosystem change than is commonly recognized. Here, we provide a review of intermediate-severity disturbances that includes proposed criteria for categorizing disturbances on the classification gradient. We propose that the canopy opening diameter to height ratio (D:H) be used to delineate gap-scale from intermediate-severity events and that the threshold between intermediate and catastrophic events be based on the influence of residual trees on the composition of the regeneration layer. We also provide examples of intermediate-severity disturbance agents, return intervals for these events, and recommendations for incorporating natural intermediate-severity disturbance patterns in silvicultural systems. Full article

Growing concern about forest degradation and loss, combined with the political impetus supplied by the Earth Summit in 1992, led to the establishment of eleven intergovernmental, regional, and international forest-related processes focused on the use of criteria and indicators (C&I) for sustainable forest management (SFM). Up to 171 countries have participated in these processes to apply C&I frameworks as a tool for data collection, monitoring, assessment, and reporting on SFM and on achieving various forest-related UN Sustainable Development Goals. Based on an expert survey and literature analysis we identify six interlinked impact domains of C&I efforts: (1) enhanced discourse and understanding of SFM; (2) shaped and focused engagement of science in SFM; (3) improved monitoring and reporting on SFM to facilitate transparency and evidence-based decision-making; (4) strengthened forest management practices; (5) facilitated assessment of progress towards SFM goals; and (6) improved forest-related dialog and communication. We conclude that the 25-year history of C&I work in forestry has had significant positive impacts, though challenges do remain for the implementation of C&I and progress towards SFM. The work should be continued and carried over to other sectors to advance sustainability goals more broadly. Full article

Harvest residues can play a crucial role in conserving nutrients for recycling in forests, but little is known about the rates of decomposition and nutrient release from these residues following logging in tropical acacia plantations. In this study, we examined the biomass and nutrient content of harvest residue components (bark, leaves, and branches) using the litterbag technique for a 1.5-year-period following harvest of a seven-year-old Acacia mangium plantation in Northern Vietnam. At harvest, the total dry biomass of harvest residues was 18 t ha⁻¹ comprising bark (8.9 t ha⁻¹), branches (6.6 t ha⁻¹), and leaves (2.5 t ha⁻¹). The retained bark on site conserved 51% N, 29% P, 32% K, 64% Ca, and 24% Mg content from harvest residues for recycling. Decomposition rate of the leaves was the most rapid (k = 1.47 year⁻¹; t_0.5 = 0.47 year), then branches (k = 0.54 year⁻¹; t_0.5 = 1.29 year), and bark (k = 0.22 year⁻¹; t_0.5 = 3.09 year). During decomposition, the loss of nutrients from harvest residues was K ≈ Ca > N > P> Mg. Decomposition of harvest residues and the associated rate of nutrient release can potentially supply a significant amount of nutrients required for stand development in the next rotation. Full article

Douglas-fir, the most important timber species in the Pacific Northwest, US (PNW), has high stiffness and strength. Growing it in plantations on short rotations since the 1980s has led to concerns about the impact of juvenile/mature wood proportion on wood properties. Lumber recovered from four sites in a thinning trial in the PNW was analyzed for relationships between thinning regime and lumber grade yield. Linear mixed-effects models were developed for understanding how rotation age and thinning affect the lumber grade yield. Log small-end diameter was overall the most important for describing the presence of an appearance grade, generally exhibiting an indirect relationship with the lower quality grades. Stand Quadratic Mean Diameter (QMD) was found to be the next most uniformly important predictor, its influence (positive or negative) depending on the lumber grade. For quantity within a grade, as log small-end diameter increased, the quantity of the highest grade increased, while decreasing the quantity of the lower grades differentially. Other tree and stand attributes were of varying importance among grades, including stand density, tree height, and stand slope, but logically depicted the tradeoffs or rebalancing among the grades as the tree and stand characteristics change. Structural lumber grade presence was described best by acoustic wave flight time, log position (decreasing presence in upper logs), and an increasing presence with rotation age. A smaller set of variables proved useful for describing quantity within a structural grade. Forest managers can use these results in planning to best capture value in harvesting, allowing them to direct raw materials (logs) to appropriate manufacturing facilities given market demand. Full article

Plants with ericoid mycorrhizal and ectomycorrhizal associations coexist at the tree line and in many boreal forests. Both ericoid mycorrhizal and ectomycorrhizal roots are known to produce extracellular enzymes, but ericoid mycorrhizal fungi have been demonstrated in vitro to have higher enzyme activities. On hair roots of four ericoid mycorrhizal species (Rhododendron ferrugineum, Vaccinium vitis-idaea, Vaccinium myrtillus, Calluna vulgaris) and on ectomycorrhizal and non-mycorrhizal root tips of Picea abies growing at the tree line (1700 m) in the Austrian Alps, potential activities of eight extracellular root enzymes were estimated. Our results show that the activities of all the different extracellular root enzymes were generally similar among the ericaceous plant species. The mean laccase enzyme activity of ectomycorrhizal root tips of Picea abies was significantly higher than that of both the hair roots and fine roots of the ericaceous species. Leucine-amino-peptidase activity on hair roots was significantly higher than on non-mycorrhizal fine roots for the ericaceous vegetation. However, the mean activity of β-glucuronidase of the ericaceous species was significantly higher in fine roots compared to the hair roots. Generally extracellular root enzyme activity is not higher on ericaceous roots compared to ectomycorrhizas of Picea abies. Full article