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For customer-oriented wood supply, buffering is required for flexibility to handle interactions in the wood procurement system. This includes balancing lead-time and operational cost by using stocks and production capacity as buffers. Despite the well-known challenge to balance the interactions between harvesting and forwarding in Nordic mechaniced CTL-operations, there has been limited research on how the machine groups can be staffed to enable flexibility and more focus on other measures to create flexibility. Therefore, this study explored trade-offs between wood lead-time and harvesting cost in the stump-to-roadside part of the wood supply chain by altering the numer of full-time working operators in the harvesting groups. This was done using discrete-event simulations implemented in Anylogic software. Input data included information about operational conditions in 1500 forest stands. The results revealed that the best balance was to have sufficient harvesting capacity to adjust wood lead times at the expense of increased harvesting costs. Of the tested options, the best balance was achieved when staffing a two-machine group with three operators, and thereby allocating 50% of the used work-shifts to regulating the field wood stock between the two machines. This resulted in the shortest lead times and the smallest harvesting cost increase. Compared to the option with no flexibility for stock adjustment (4 operators), the average lead-time could be reduced to one tenth at a cost increase of 3.4%. These findings have the potential to improve decisions of how harvesting groups are staffed to balance specific objectives of desired lead times and costs, which migh prove to be a valuable addition to the already used measures to manage wood flow. [ABSTRACT FROM AUTHOR]

Restoration of degraded habitat is frequently used in ecological compensation. However, ecological restoration suffers from innate problems of long delivery times of features shown to be good proxies for biodiversity, e.g., large dead trees. We tested a possible way to circumvent this problem; the translocation of hard-to-come deadwood substrates from an impact area to a compensation area. Following translocation, deadwood density in the compensation area was locally equivalent to the impact area, around 20 m3 ha−1, a threshold for supporting high biodiversity of rare and red-listed species. However, deadwood composition differed between the impact and compensation area, showing a need to include more deadwood types, e.g., late decomposition deadwood, in the translocation scheme. To guide future compensation efforts, the cost for translocation at different spatial scales was calculated. We conclude that translocation of deadwood could provide a cost-efficient new tool for ecological compensation/restoration but that the method needs refinement. [ABSTRACT FROM AUTHOR]

Even though stumpwood may become a significant part of the future fuel mix for combined heat and power plants in Sweden, the harvesting of stumps after regeneration felling is still only performed on a trial basis. Results from time studies on two, 23 tonne, excavators fitted for stump lifting, together with follow-up data on stump lifting and forwarding, are presented. Lifting, splitting, and piling the stumps accounted for 17, 32, and 32%, respectively, of the total productive work time. A predictive model was developed to estimate operational times and productivities when lifting pine and spruce stumps. Stump diameter, species, and terrain conditions contributed significantly to the fit of the model. The model predicts that productivity of stump lifting in spruce sites with easy terrain conditions and average stump diameters of 20 and 40 cm will be 1.23 and 4.19 oven-dry tonnes (ODT) per productive work hour, respectively. This is 43% higher than in pine sites with difficult terrain conditions and the same diameters. In the follow-up data, the productivity in stump lifting varied from 1.5 to 2.9 ODT per productive work hour while the cost for lifting and extraction to roadside varied from 37.8 to 59.4 €/ODT. [ABSTRACT FROM AUTHOR]

Autonomous navigation in forest terrain, where operation paths are rarely straight or flat and obstacles are common, is challenging. This paper evaluates a system designed to autonomously follow previously demonstrated paths in a forest environment without loading/unloading timber, a pre-step in the development of fully autonomous forwarders. The system consisted of a forwarder equipped with a high-precision global positioning system to measure the vehicle's heading and position. A gyro was used to compensate for the influence of the vehicle's roll and pitch. On an ordinary clear-cut forest area with numerous stumps, the vehicle was able to follow two different tracks, three times each at a speed of 1 m s-1, with a mean path tracking error of 6 and 7 cm, respectively. The error never exceeded 35 cm, and in 90% of the observations it was less than 14 and 15 cm, respectively. This accuracy is well within the necessary tolerance for forestry operations. In fact, a human operator would probably have a hard time following the track more accurately. Hence, the developed systems function satisfactorily when using previously demonstrated paths. However, further research on planning new paths in unknown unstructured terrain and on loading/unloading is required before timber transports can be fully automated. [ABSTRACT FROM AUTHOR]

Abstract: Firewood is society’s oldest source of household energy and is still extensively used around the world. However, little is known about firewood usage in technologically advanced countries with high energy consumption. Some key issues include quantities of firewood currently used and future trends, as well as the influence of this usage on available biomass resources. This study addresses those issues through a postal questionnaire to 1500 of the firewood using households in a region in Northern Sweden. One-third of households produced 11–20 solid m3 of firewood per year. Three-fourths expected their production to be unchanged or increase during the coming five years. A large proportion of young producers indicated long-term continuation of firewood usage. Half (53%) of the firewood producing households owned forest and thereby had free access to wood. Produced firewood volume corresponded to 4–8% of the region’s roundwood volume harvested for industrial purposes. The use of firewood is suggested to influence decisions of private forest owners about management and harvest of forest biomass, and, thus, affect supply for bioenergy and other uses. With further incorporation of firewood usage into forest biomass management regimes, larger biomass quantities are likely to be available for industrial uses. [ABSTRACT FROM AUTHOR]

This study evaluated the costs, (O2 emissions, and energy balances associated with three potential systems for recovering roadside slosh in British Columbia, Canada, in which the biomass is transported as slash, hog fuel, or bundles. Costs, (O2 emissions, and energy balances of all three systems showed strong dependence on transportation distance and considerably weaker dependence on slosh amounts at landing (cutting block size). The results indicated that the hog fuel system is the cheapest, per unit of delivered biomass, whereas the bundle system is the most expensive system when transportation distances ore short (<100 km), and the slosh system is the most expensive when transportation distances exceed 100 km. However, the viability of the systems is strongly dependent on payload assumptions. [ABSTRACT FROM AUTHOR]

Abstract: Half of all Swedish forests are owned by private individuals, and at least 215,000 people work in these privately owned forest holdings. However, only lethal accidents are systematically monitored among self-employed forest workers. Therefore, data from the registries of the Swedish Work Environment Authority, the Labor Insurance Organization and the regional University Hospital in Umeå were gathered to allow us to perform a more in-depth assessment of the rate and types of accidents that occurred among private forest owners. We found large differences between the registries in the type and number of accidents that were reported. We encountered difficulties in defining “self-employed forest worker” and also in determining whether the accidents that did occur happened during work or leisure time. Consequently, the estimates for the accident rate that we obtained varied from 32 to ≥4300 injured persons per year in Sweden, depending on the registry that was consulted, the definition of the sample population that was used, and the accident severity definition that was employed. Nevertheless, the different registries gave a consistent picture of the types of accidents that occur while individuals are participating in self-employed forestry work. Severe accidents were relatively common, as self-employed forestry work fatalities constituted 7% of the total number of fatalities in the work authority registry. Falling trees were associated with many of these fatal accidents as well as with accidents that resulted in severe non-fatal injuries. Thus, unsafe work methods appeared more related to the occurrence of an accident than the equipment that was being used at the time of the accident (e.g., a chainsaw). Improvement of the workers’ skills should therefore be considered to be an important prevention measure that should be undertaken in this field. The challenges in improving the safety in these smallest of companies, which fall somewhere between the purview of occupational and consumer safety, are exemplified and discussed. [Copyright &y& Elsevier]

Abstract: Firewood is commonly used around the world, but little is known about the work involved in its production and associated accidents. The objectives were to identify relationships between accidents and time exposure, workers’ age and sex, equipment used and work activities in family forestry''s firewood production. Data from a postal survey in Northern Sweden were compared to a database of injuries in the same region. Most accidents occurred to 50–69 year old men, who also worked most hours. No significant differences in sex and age were found between expected and recorded accident frequencies when calculated from total work hours; however, when calculated using numbers of active persons significant differences were found for both age and sex. Frequency of accidents per unit worked time was higher for machine involving activities than for other activities. Accidents that occurred when using wedge splitter machines were responsible for most of this overrepresentation. Fingers were the most commonly injured body parts. Mean accident rate for the equipment used was 87 accidents per million work hours, and the rate was highest for wedge splitters (122 accidents per million work hours). Exposure to elevated risks due to violation of safety procedures is discussed, as well as possible preventative measures. [Copyright &y& Elsevier]

As various methods for precision inventories, including light detection and ranging (LiDAR), are becoming increasingly common in forestry, planning at the individual-tree level is becoming more viable. In this study, we present a method for finding the optimal thinning times for individual trees from an economic perspective. The method utilizes a forest growth model based on individual trees that has been fitted to Norway spruce (Picea abies (L.) Karst.) stands in northern Sweden. We find that the optimal management strategy is to thin from above (i.e., harvesting trees that are larger than average). We compare our optimal strategy with a conventional management strategy and find that the optimal strategy results in approximately 20% higher land expectation value. Furthermore, we find that for the optimal strategy, increasing the discount rate will reduce the final harvest age and increase the basal area reduction. Decreasing the cost to initiate a thinning (e.g., machinery-related transportation costs) increases the number of thinnings and delays the first thinning. [ABSTRACT FROM AUTHOR]

This document is a correction notice for an article titled "Translocation of deadwood in ecological compensation: A novel way to compensate for habitat loss." The correction addresses an error in one of the equations presented in the article, specifically related to the calculation of the geometrical form of a truncated cone. The correct version of the equation is provided in the correction notice. The original article has been corrected. The correction notice is authored by Olov Tranberg, Anne-Maarit Hekkala, Ola Lindroos, Therese Löfroth, Mari Jönsson, Jörgen Sjögren, and Joakim Hjältén. [Extracted from the article]

Farm tractor + trailers play a key role in wood transportation after forests are logged. Despite of the fact that a forwarder is a forestry vehicle that carries felled logs for shorter distances off the ground, tractors are still used in some forest areas of the world, such as the Hyrcanian forest in northern Iran. This study was conducted to investigate the possibility of using both the light forwarder and forestry trailer instead of a farm tractor + trailer in wood transportation. The optimal machine option for wood transportation is determined using goal programming model in the study area. In this paper, multi-objective goals (such as economic, operational, environmental and ergonomic) were considered. The results showed that considering only the economic goal, the contractor could save up to 44% in costs by purchasing and replacing a forestry trailer with a 2-wheel trailer attached to the farm tractor. In addition, considering various goals, a light forwarder could be selected as the optimal machine. Currently, the most important objectives of all forest contractors are to establish economic goals and reduce wood transportation costs. Since other goals, such as environmental and ergonomic, are also important; it is suggested that multi-objective approaches should use for planning. [ABSTRACT FROM AUTHOR]

Size and spatial distribution of trees are important for forest stand growth, but the extent to which it matters in thinning operations, in terms of wood production and stand economy, has rarely been documented. Here we investigate how the choice of spatial evenness and tree-size distribution of residual trees impacts wood production and stand economy. A spatially explicit individual-based growth model was used, in conjunction with empirical cost functions for harvesting and forwarding, to calculate net production and net present value for different thinning operations in Norway spruce stands in Northern Sweden. The in silico thinning operations were defined by three variables: (1) spatial evenness after thinning, (2) tree size preference for harvesting, and (3) basal area reduction. We found that thinning that increases spatial evenness increases net production and net present value by around 2.0%, compared to the worst case. When changing the spatial evenness in conjunction with size preference we could observe an improvement of the net production and net present value up to 8.0%. The magnitude of impact differed greatly between the stands (from 1.7% to 8.0%) and was highest in the stand with the lowest stem density. [ABSTRACT FROM AUTHOR]

Ground-based mechanized forestry requires the traversal of terrain by heavy machines. The routes that they take are often called "machine trails" and are created by removing trees from the trail and placing the logs outside it. Designing an optimal machine trail network is a complex locational problem that requires understanding how forestry machines can operate on the terrain, as well as the trade-offs between various economic and ecological aspects. Machine trail designs are currently created manually based on intuitive decisions about the importance, correlations, and effects of many potentially conflicting aspects. Badly designed machine trail networks could result in costly operations and adverse environmental impacts. Therefore, this study was conducted to develop a holistic optimization framework for machine trail network design. Key economic and ecological objectives involved in designing machine trail networks for mechanized cut-to-length operations are presented, along with strategies for simultaneously addressing multiple objectives while accounting for the physical capabilities of forestry machines, the impact of slope, and the operating costs. Ways of quantitatively formulating and combining these different aspects are demonstrated, together with examples showing how the optimal network design changes in response to various inputs. [ABSTRACT FROM AUTHOR]

Competition for woody biomass between material and energy uses is expected to further increase in the future, due to the limited availability of forest resources and increasing demand of wood for material and bioenergy. Currently, methodological approaches for modeling wood production and delivery costs from forest to industrial gates are missing. This study combines forest engineering, geographically explicit information, environmental constraints and economics in a bottom-up approach to assess cost–supply curves. The estimates are based on a multitude of wood supply systems that were assigned according to geographically explicit forestry characteristics. For each harvesting and transportation system, efficiencies were modeled according to harvesting sites and main delivery hubs. The cost–supply curves for roundwood and logging residues as estimates for current time and for the future (2030) show that there are large regional differences in the potential to increase extraction in the EU28. In most EU Member States, the costs of logging residues extraction increase exponentially already for low levels of mobilization, while extraction of roundwood can be increased to a larger extent within reasonable costs (30–40 $/m3). The large differences between countries in their harvest potential highlight the importance of spatially explicit analyses. [ABSTRACT FROM AUTHOR]

There is a need to decrease the costs of cut-to-length operations. The harwarder, a one-machine system with the potential to reduce the costs, has been compared to the two-machine system (TMS) at the stand and regional levels but not at the national level, which is important as basis for decision to implement. The objective was therefore to analyze its potential on a large scale in Swedish final fellings. It was evaluated using two modeling approaches in conjunction with data representing around 30% of Sweden's yearly final fellings from five forestry organizations. The analyses revealed that total costs could be reduced by around 3% if up to 50% of the total volume was logged using harwarders rather than the TMS. This would require the introduction of up to 250 harwarders into machine fleets that currently use only the TMS. The two modeling approaches gave similar results. It was concluded that the harwarder may need to demonstrate greater potential to justify a full-scale implementation in Swedish forestry, but the machine could be improved through technological development, especially through automation. [ABSTRACT FROM AUTHOR]

In conventional mechanized cut-to-length systems, a harvester fells and cuts trees into logs that are stored on the ground until a forwarder picks them up and carries them to landing sites. A proposed improvement is to place logs directly into the load spaces of transporting machines as they are cut. Such integrated loading could result in cost reductions, shorter lead times from stump to landing, and lower fuel consumption. However, it might also create waiting times for the machines involved, whereas multifunctional machines are likely to be expensive. Thus, it is important to analyze whether or not the advantages of any changes outweigh the disadvantages. The conventional system was compared with four potential systems, including two with autonomous forwarders, using discrete-event simulation with stochastic elements in which harvests of more than 1000 final felling stands (containing in total 1.6 million m3) were simulated 35 times per system. The results indicate that harwarders have substantial potential (less expensive on ≥80% of the volume and fuel consumption decreased by ≥18%) and may become competitive if key innovations are developed. Systems with cooperating machines have considerably less potential, limited to very specific stand conditions. The results conform with expected difficulties in integrating processing and transporting machines' work in variable environments. [ABSTRACT FROM AUTHOR]

The extensive outsourcing of forest harvesting operations means that the operational performance of contractors has an immense impact on the forest industry supply chain. This study describes perceived drivers and obstacles for strong performance in harvesting service based on semi-structured interviews with four production supervisors and eight contractors. The analysis of interview data revealed a wide array of factors considered to drive or hinder the performance. The factors were categorized into five types: Capability, Incentives, Commitment, Involvement and External factors. Factors concerning Capability, especially resources and competence, were most frequently considered by production supervisors as both drivers and hinders. The contractors considered most commonly Incentives to affect performance, especially motivation and strategy, as drivers and the economy as hinder. Both parties considered lack of resources as hinder to performance. For competence, relationship and collaboration interface, on the other hand, the two parties had different views on whether they acted as drivers or hinders. The knowledge presented in this paper is of interest to researchers or practitioners who wishes to understand the complexities underlying successful harvesting service performance. The insights can contribute to the reshaping of business practices to better target and leverage the mechanisms that most strongly affect performance. [ABSTRACT FROM AUTHOR]

Study Design: Human volunteers were exposed experimentally to single-sided mechanical shocks (SSMS) and double-sided mechanical shocks (DSMS) while seated.Objective: The aim of this study was to describe and contrast seated postural reactions due to SSMS or DSMS in healthy male adults.Summary Of Background Data: Mechanical shocks to the body, caused when driving on irregular terrain, are suggested to be hazardous to the spine and may be associated with the reported musculoskeletal pain of the back and neck among professional drivers. However, very little is known about the characteristics of seated postural reactions and the biomechanical effects caused by mechanical shocks.Methods: Twenty healthy male subjects (18-43 years old) were exposed while seated to 5 SSMS and 15 DSMS in lateral directions. The second acceleration in the DSMS was in the opposite direction to the first acceleration and was fast, medium, or slow depending on the speed of direction change. Surface electromyography (EMG) was recorded in muscles of the upper neck, trapezius, erector spinae, and external oblique, while kinematics were recorded with inertial sensors placed at the neck, trunk, and pelvis. Muscle activity was normalized to maximum voluntary contractions (MVCs).Results: The EMG amplitudes were significantly higher (0.6-1%; P < 0.001) for the fast DSMS than all other shocks. Range of motion (ROM) of the neck and trunk was greater during the DSMS than the SSMS. Evoked muscle activity was less than 2% MVC in the trapezius, less than 10% MVC in the erector spinae and upper neck, while the activity exceeded 10% MVC in the external oblique muscles.Conclusion: Fast DSMS in lateral directions appear more demanding than SSMS, demonstrating augmented seated postural reactions. However, the present mechanical shocks employed did not seem to induce postural reactions with regard to ROM or muscle activity of a magnitude likely to cause musculoskeletal overload.Level Of Evidence: 4. [ABSTRACT FROM AUTHOR]

• An optimization model for forest machine-trail network design is presented. • A novel greedy metaheuristic for obtaining optimal network designs is presented. • Four search scenarios aiming to find the optimal location of trails are offered. • The algorithm outperforms the solutions obtained by manual traditional methods. Designing an optimal machine trail network is a complex locational problem that requires an understanding of different machines' operations and terrain features as well as the trade-offs between various objectives. With the overall goal to minimize the operational costs of the logging operation, this paper proposes a mathematical optimization model for the trail network design problem and a greedy heuristic method based on different randomized search scenarios aiming to find the optimal location of machine trails —with potential to reduce negative environmental impact. The network is designed so that all trees can be reached and adapted to how the machines can maneuver while considering the terrain elevation's influence. To examine the effectiveness and practical performance of the heuristic and the optimization model, it was applied in a case study on four harvest units with different topologies and shapes. The computational experiments show that the heuristic can generate solutions that outperform the solutions corresponding to conventional, manual designs within practical time limits for operational planning. Moreover, to highlight certain features of the heuristic and the parameter settings' effect on its performance, we present an extensive computational sensitivity analysis. [ABSTRACT FROM AUTHOR]

Accurate vehicle localization in forest environments is still an unresolved problem. Global navigation satellite systems (GNSS) have well known limitations in dense forest, and have to be combined with for instance laser based SLAM algorithms to provide satisfying accuracy. Such algorithms typically require accurate detection of trees, and estimation of tree center locations in laser data. Both these operations depend on accurate estimations of tree trunk diameter. Diameter estimations are important also for several other forestry automation and remote sensing applications. This paper evaluates several existing algorithms for diameter estimation using 2D laser scanner data. Enhanced algorithms, compensating for beam width and using multiple scans, were also developed and evaluated. The best existing algorithms overestimated tree trunk diameter by ca. 40%. Our enhanced algorithms, compensating for laser beam width, reduced this error to less than 12%. [ABSTRACT FROM AUTHOR]

Abstract: Wheel slip may increase the risk for wheel rutting and tear up ground vegetation and superficial roots and thereby decreasing the bearing capacity of the ground, but also reducing the growth of nearby standing forest trees. With increased slip, more energy is consumed for making wheel ruts in the ground, with increased fuel consumption as a result. This paper proposes a novel method for measuring slip in an uneven forest terrain with an 8WD forestry machine. This is done by comparing the wheel velocity reported by the machine and velocity measured with an accurate DGPS system. Field tests with a forestry machine showed that slip could be calculated accurately with the suggested method. The tests showed that there was almost no slip on asphalt or gravel surfaces. In a forest environment, 10–15% slip was common. A future extension of the method enabling estimation of the slip of each wheel pair in the bogies is also suggested. [Copyright &y& Elsevier]