Tomas Nordfjell

Productivity and Costs in Shelterwood Harvesting

Harvesting costs have a significant influence on the application and potential use of the shelterwood system. These costs are strongly related to the time needed for the logging operations. In this study, which was carried out in Norway spruce [Picea abies (L.) Karst.] stands in northern Sweden, the effective time (E 0) of a single-grip harvester in shelterwood cutting, thinning of shelterwoods and clearcutting was measured. Based on these data the costs of shelterwood harvestings and clearcutting were calculated and compared. It was found that (1) the time per tree in shelterwood cutting and thinning of shelterwoods was greater than in clearcutting, (2) the time per cubic metre was higher in sparse shelterwoods than in dense shelterwoods, (3) most of this increase was due to longer driving time because fewer trees were harvested, and (4) the longer time and higher logging costs in the shelterwood system (compared with the clearcutting system) were mostly related to the establishment of the shelterwood. It was concluded that the shelterwood alternative is especially competitive when it is desirable to maximize the share of saw logs at the expense of pulpwood.

A conceptual model for understanding social practices in family forestry

This paper presents a conceptual model for better understanding of the various aspects or phenomena in family forestry. In this model, land is considered as the basic resource around which work and family life are organised. With the land follows specific property rights, giving the children, as a result of marriage, the right to inheritance. To generate revenue from the capital invested or to increase the value of the property, self-employment in practical work and decision-making is needed. Taxes are charged on the revenue of the property. Gender has an impact on inheritance position, division of work, and pattern of marriage. By connecting these institutions or concepts to each other with threads of social practices, a ‘cobweb model’ is developed which allows the structure of the social reality in family forestry to be visualised. The cobweb model has been applied in order to examine social practices in contemporary Swedish family forestry. Results based on a nationwide survey, reveal significant differences between different forest owner categories regarding the impact of gender, inheritance, marriage, property rights and self-employment. Furthermore, the analytical potential of the model is demonstrated.

Assessing the Utility of Two Integrated Harvester-Forwarder Machine Concepts Through Stand-Level Simulation

Abstract The relative performance of two integrated machine concepts (combined harvesting / forwarding capabilities) was assessed against a conventional harvester / forwarder CTL system in a simulated thinning regime. Multiple-regression based on the simulation output was used in deriving time-consumption functions at the systems and machine level. Descriptive stand variables could be reduced to; harvest volume (m3/ha), stem volume (m3), lead distance (m) and object volume (m3/stand) while maintaining acceptable statistical rigour (R2 > 0.95). The ability of one of the integrated machines to process logs directly onto the bunk provided it with an advantage that more than compensated for its reduced harvesting efficiency. Both integrated machine systems show a competitive advantage in forest structures with low object volumes and long or frequent relocations. Factors negatively affecting forwarding productivity (e.g. long lead distances) favour the conventional two- machine system. A break-even economic analysis showed that integrated machines could present a feasible alternative to contemporary mechanised CTL systems.

Autonomous forest vehicles: historic, envisioned, and state-of-the-art.

Abstract The feasibility of using autonomous forest vehicles (which can be regarded as logical developments in the ongoing automation of forest machines), the systems that could be applied in them, their potential advantages and limitations (in the foreseeable future) are considered in this paper. The goals were to analyze: 1) the factors influencing the degree of automation in logging; 2) the technical principles that can be applied to autonomous forest machines, and 3) the feasibility of developing an autonomous path-tracking forest vehicle. A type of vehicle that is believed to have considerable commercial potential is an autonomous forwarder. The degree of automation is influenced by increased productivity, the machine operator as a bottle-neck, cost reduction, and environmental aspects. Technical principles that can be applied to autonomous forest vehicles are satellite navigation, wheel odometry, laser scanner, and radar. A new path-tracking algorithm has been developed to reduce deviations from the desired path by utilizing the driver’s steering commands. The presented system has demonstrated both possibilities and difficulties associated with autonomous forest machines. A field study has shown that it is quite possible for them to learn and track a path previously demonstrated by an operator with an accuracy of 0.1 m on flat ground and also to detect and avoid unexpected obstacles. Although the forest machine safely avoids obstacles, the study shows that further research in the field of obstacle avoidance is needed to optimize performance and ensure safe operation in a real forest environment.

Pine and spruce stump harvesting productivity and costs using a Pallari KH 160 stump-lifting tool.

Abstract 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.

Fuel Consumption In Forwarders

Abstract Forwarder fuel consumption was studied by examining a total of 27 forwarders under field conditions. Three datasets, representing different data acquisition methods, were used. In a field study, time and fuel consumption by work-element of two 20–21 tonne forwarders in final felling were recorded. In a questionnaire survey, daily data concerning fuel consumption, productivity and average extraction distance was provided on 18 forwarders, divided between final felling and thinning. Finally, accounting data on fuel consumption for 11 forwarders were obtained. In the field study, the fuel consumption varied between 8.3 to 15.7 l/PMH (productive machine hour) for different work elements. The total fuel consumption was 0.28–0.36 l/m3sub (solid under bark) at average extraction distances on 360–412 m for loads of sawlogs and 0.43–0.66 l/m3sub (458–514 m) for loads of pulpwood. 61–62% of that fuel was consumed during loading and driving during loading. The forwarders consumed 0.23–0.38 l/100 m driving and the difference was only 10% with and without load. In the questionnaire survey, the fuel consumption averaged 0.62 l/m3sub (sawlogs and pulpwood, 318 m average extraction distance) for final felling (16–20 tonne forwarders) and 0.92 l/m3sub (644 m) for thinning (11–14 tonnes). An exception was 2.5 tonne forwarders that consumed only 0.35–0.37 l/m3sub (120–180 m). 89% of the extracted volume in the accounting data was from thinnings and the fuel consumption was in average 0.67 l/m3sub (100–200 m) for 9 to11 tonne forwarders. More difficult terrain conditions, the use of tracks and wheel-chains and one more assortment in the questionnaire survey are the most probable reasons for higher fuel consumption than in the field study. At long extraction distances it is especially important to utilize the maximum load capacity to benefit low fuel consumption on m3 basis.

Swedish non-industrial private forest owners: a survey of self-employment and equipment investments

It has been estimated that Sweden’s non-industrial private forest (NIPF) owners undertake a total of 12 M hours of self-employed forest work per year. This paper reports an evaluation of self-employment in Swedish NIPF’s in terms of the people and equipment involved. NIPF owners’ self-employment was determined by a nationwide survey. Complete equipment sales statistics were compiled from interviews with manufacturers and importers. About 66% of NIPF owners are undertaking self-employed forestry work. Pre-commercial thinning was the activity undertaken most frequently by them, followed by planting, cutting and extraction. In comparison to other NIPF owners, self-employed NIPF owners tend to be younger, and are more likely to be male, single owners, resident on holdings, farmers and members of forest owner associations. Sales of new equipment suitable for self-employed individuals amounted to €67 M, or 83,000 items. Based on sales numbers and the profile of self-employed NIPF owners, no major changes in the amount and nature of self-employment are expected in the near future.

Energy use and emissions due to the manufacture of a forwarder

The aim of the study was to assess the amount of energy input and emissions of CO2, CO, NOx, SOx, N2O, HC, CH4 and particles discharge to the environment in association to the following stages of a forwarders life cycle; (1) material premanufacturing, (2) fabrication of individual components, (3) assembly of the vehicle, and (4) associated transports. The premanufacturing phase accounted for 65% of the total energy consumption, 70% of the CO2 emissions, 95% of CO emissions and 65% of the NOx emissions. Transports showed the smallest contribution to the environmental impact among the forwarder life cycle phases examined.

Compressing and Drying of Bunched Trees from a Commercial Thinning

This study focuses on the power needed to compress bunches of tree-parts (undelimbed trees, cross-cut into two or more pieces) and the change in moisture content of bunches during air-drying. Thirty-five bunches (green weights 209-954 kg) were formed, 5.5 m long. The bunches were compressed by a chain being wound once around them at three points and tightened, one at a time. The bunches were air-dried and then chipped. A small bunch was more tightly compressed at a specific force than a large bunch. The bulk density (green weight) was 270-460 kg m-3 (16 kN compression) and 520-780 kg m-3 (53 kN compression). Small forces resulted in a higher bulk density for pine or birch bunches than for spruce bunches, while large forces caused the opposite result. A compressed bunch dried almost as well as if not compressed. Chipping bunches was found to be less time consuming than chipping individual trees.

Simulation of harvester productivity in selective and boom-corridor thinning of young forests

Abstract Forest management practices may change in the future, due to increases in the extraction of forest fuel in first thinnings. Simulation models can be used to aid in developing new harvesting systems. We used such an approach to assess the productivity of innovative systems in various thinnings of young stands with wide ranges of mean breast height diameter (1.5–15.6 cm), stems per hectare (1000–19,100), and mean height (2.3–14.6 m). The results show that selective multiple-tree-handling increases productivity by 20–46% compared to single-tree-handling. If the trees are cut in boom-corridors (10×1 or 2 m strips between strip roads), productivity increases up to 41%, compared to selective multiple-tree-handling. Moreover, if the trees are felled using area-based felling systems, productivity increases by 33–199%, compared to selective multiple-tree-handling. For any given harvesting intensity, productivity increased the most in the densest stands with small trees. The results were used to derive time consumption functions. Comparisons with time study results suggest that our simulation model successfully mimicked productivity in real-life forest operations, hence the model and derived functions should be useful for cost calculations and evaluating forest management scenarios in diverse stands.