Volume 16, numéro 2, july 2005

EN :

Cut-to-length (CTL) harvesting systems involving small and large harvesters and a forwarder were simulated using a modular computer simulation model. The two harvesters simulated were a modified John Deere 988 tracked excavator with a single grip sawhead and a Timbco T425 based excavator with a single grip sawhead. The forwarder used in the simulations was a Valmet 524 machine with 2.4-meter log bunks. Production rates and costs were examined for a wide range of even-age oak forest stand conditions. The simulation results suggest that when the tree's DBH is less than 26 cm, harvesting using the Timbco T425 is about 30% more expensive than using the John Deere 988. However, if the tree is larger than 26 cm of DBH, the unit cost of the Timbco T425 was about 8% less than that of the John Deere 988. The balanced John Deere 988 CTL system was 31% more productive and 8% more expensive than the balanced Timbco T425 CTL system in the 20 to 36 cm DBH range. General regression equations were developed for estimating the productivity and cost for the range of conditions simulated. The results should be valuable to managers, planners, and loggers considering the use of CTL systems in this region.

EN :

Nine chippers were tested for particle size distribution, in order to a) see how chips produced with these machines matched the quality specifications set by the district heating plants of Northeastern Italy and b) detect significant differences between machines. The benchmark was set by collecting chip samples from fourteen district heating plants in the region of interest. The effect of operator skill was minimized and all machines were fed with the same assortment: logs, supplied in lengths varying between 2.4 and 6 m. All logs had similar moisture contents, which typically ranged between 33 and 37 % on a fresh weight base. Mobile in-woods chippers fed with limb-free logs produce high-quality chips, whose particle size distribution matches that of the best chips normally fed to the Italian district heating plants. Indeed, all the tested machines produced chip samples containing almost no oversize particles, very little fines (0.5 to 1 %), and a large majority of chips within the 3-45mm range (95 to 99 %), except the auger-equipped Laimet, which is designed to produce larger chips. There were statistically significant differences between machines and machine types, which were not affected by possible variations of the tree species processed.

EN :

Wood procurement logistics has developed dramatically during the last few decades. The adaptation of general logistics theory, increasing customer orientation, product-based bucking, the externalization of work processes, the expansion of international wood trade and the rapid development of management tools and methods have changed the characteristics of wood procurement tremendously. Consequently, there is a growing need to redefine the concept of wood procurement. This paper attempts to lay down a general framework for CTL (cut-to-length) method-based wood procurement management and to highlight the most important research and development objectives in this area.

In wood procurement the main customer service goals are price, dimensional requirements, quality requirements and the ability to react to changes. The price is always important, but the smaller the proportion the wood cost is of the total production costs, the less significant the price becomes. The importance of quality and dimensional requirements increases with the rising value of wood. Due to improved inventory booking systems and transportation optimization systems, wood procurement companies have managed to decrease stock levels, thus decreasing rate costs. The company may aim to decrease the level of stock, but not without possible additional costs. According to logistics theories, an increase in stock levels increases storage costs but, on the other hand, a decrease of stock levels increases transportation costs and the risk of lost profit.

Seasonal variation and the ability to react to changes have great significance to logistics costs in wood procurement. Small stumpage reserves inevitably lead to expensive harvesting and transportation activities. But more research should, in the future, also be directed at improving classifications of harvesting and transportation accessibility.

In the Nordic countries significant progress both in tree bucking control and transportation allocation has been achieved in practice, but they are still considered as separate processes. It is in most cases undesirable to cut many products from the same stand, since it implies too many loading and transportation operations. Therefore, it is necessary to choose which products in what quantities may be cut from each stand. This means that tree bucking control and wood transportation problems should not be considered as separate tasks, but instead be optimized as a whole. If they are considered as separate processes the gains achieved through better product characteristics are lost in increasing transportation costs. Current wood pricing systems make it difficult to fully exploit the advantage that could be gained through this kind of optimization.

EN :

The sawmilling industry is facing serious challenges; intensified competition, increasing substitution of wood for new materials and powerful customers posing extensive new demands.

Obstacles for a change towards a more competitive configuration of the sawmilling industry are context and contingency related. Corporate strategy building must be based on an analysis of such factors. A contingency analysis of the sector reveals an array of factors that underpin severe fragmentation. Thus, sawmills have limited possibilities to exert power within the sawn wood supply chain. To break free from the ties of sector fragmentation, business level strategy may be based on

cost advantages based on scale, production technology and productivity, a competitive strategy traditional to the sawmilling industry.

market domination through new/superior products and unique offers to customers. The development of new products, such as EWP, and closer co-operation with customers such as power retailers are examples of the second type of strategy.

optimisation of raw material flows based on market information. Control and management of raw material flows is important for the sawmilling industry, as well as for other industries with similar production.

A sawmill with superior control of the inbound sawlogs will always have the upper hand on competition because it may produce and sell its products with high efficiency. In spite of their importance, these areas have received only limited attention. Controlled procurement, flexible management of forest operations and communication of short-term needs to the suppliers are vital issues for the purchasing sawmills, yet to be explored.

EN :

This paper presents the transport game; a pedagogical tool developed to provide a competition-driven introduction to important issues in transport planning. The competitive element of the game concerns minimizing transportaton. The game is played between three two-player teams. Each team has wood supply responsibility for a pulp mill and a saw mill. Given a varying weekly demand for each mill, the teams procure round wood from the 64 supply nodes in the region. The planning decisions in the game are aimed at minimizing the total transport distance (loaded + unloaded) for the weekly demand. Planning decisions have the following priority: 1) filling the mill demand, 2) minimizing the loaded transport distance by purchasing wood close to the mill 3) minimizing the unloaded transport distance by identifying backhauls flows.

The game forces the players to manually handle a high number of decision alternatives without any form of decision support. It is used to give the students a practical understanding of basic issues to accompany their theoretical lessons. It can also be used as an experimental laboratory to examine the effect of different restrictions on proficiency. The paper presents results from student exercises where development of player proficiency is examined.

EN :

Road sediment yields reaching streams over a twenty year period were modeled under two scenarios for a 4900 ha forest in the foothills of the Oregon Coast Range. In the "clustered" scenario all forest harvesting activity took place in the northern half of the forest. In the "dispersed" scenario the same level of forest harvesting activity was allocated to the full forest estate. Three spatial modeling packages were used: SPECTRUM was used to schedule the harvest settings over a 150 year period, NETWORK 2000 was used to determine which roads would be used during the first 20 years of harvest and how many truck loads would be transported over them, and SEDMODL2 was used to determine the road sediment yields likely to reach a stream. Concentrating the forest harvesting activity on half of the forest estate resulted in a 36% reduction in total road sediment yields when compared with dispersed forest harvesting activity. Fewer roads would generate sediment under the "clustered" scenario but traffic intensities on these roads would be greater, partially negating the sediment yield savings.

EN :

In order to locate a path between two known locations on a ground surface, a large number of alternative paths should be evaluated considering physical, economical, and environmental factors. Optimization techniques can be used to search for a path that minimizes the total costs while satisfying the design and environmental constraints. These techniques can result in considerable time savings in forest road design. Initially, these optimization techniques have been applied to highway design and recently, they have been applied to forest road design. This paper describes the evolution of the optimal route location systems used in both highway and forest road design based on ten criteria. The paper concludes by describing some of the unsolved problems in forest road design.

EN :

Stump heights were measured on six clear-cut blocks in the central interior of British Columbia using a systematic sampling method. Felling method, ground slope, species and stump diameter were analyzed to determine their effect on stump height. Mechanized felling with a feller-buncher resulted in lower stumps by 5.5 cm on average than those from manual felling with a chainsaw. The wide range (9.6 cm to 23.4 cm) of the average stump heights sampled from six clear-cut units indicates that other factors such as slope, species and stump diameter may influence stump height. When considering tree species, the feller-buncher left lower stump heights for subalpine fir and white spruce, while chainsaw felling resulted in lower stumps for Douglas-fir. Average stump and feller-buncher stump heights tended to increase as percent slope increased up to 45%, but the opposite trend was found in chainsaw felled sites with slopes greater than 45%. Both feller-buncher and chainsaw felling methods resulted in lower stumps as the average stump diameter increased. On ground slopes less than 30% and stump diameters between 30 and 70 cm, our analysis suggested that feller-buncher felling resulted in lower stump heights than chainsaw felling. Chainsaw felling can cause stump-pulls, slabs, and unevenness at the bottom of the tree being felled, requiring a further reduction of wood that could potentially be used for solid wood products. Feller-buncher felling, however, results in greater wood volume waste as the result of a thicker saw blade kerf than does chainsaw felling.

EN :

High costs, increasing density and height of young stands at the time of pre-commercial thinning, and difficulty in attracting personnel to do motor-manual work have called for the development of new techniques for pre-commercial thinning. In the study reported here a new motor-manual and mechanized pre-commercial thinning technique was compared to the conventional brush saw technique in terms of time requirements and damage caused to crop trees. The motor-manual tools tested were a hacksaw and two pole saws with modified chainsaw blades. The mechanized machine prototype was built especially for pre-commercial thinning, and was equipped with a new type of crane tip-mounted device based on a cutting-squeezing technique. Our expectations were that, compared to the brush saw, themechanized approach would be less time-demanding in dense and/or large diameter stands, but more main stems would be damaged. Furthermore, a motor-manual device with a larger cutting area than the conventional brush saw blade should allow faster operation in dense and large diameter stands, without damaging higher numbers of main stems.

To test these beliefs, a rig was built that enabled the tools to be compared in experimental stands with different densities and diameters of secondary stems.

One of the pole saws and the mechanized prototype machine were competitive with the conventional brush saw in terms of both time requirements and frequency of damage to main stems, especially in dense (i.e. >15000 stems ha-1) and large diameter (>4 cm) stands. The pole saw was competitive despite having a less powerful engine. The mechanized prototype showed more homogenous time consumption, with lower variation than the other tools. Further field studies are needed to compare the tools in economic terms.

EN :

We report on the development of a new decision support system for transportation planning in Swedish forestry. The system deals both with strategic and tactical decisions. Strategic decisions concern usage of train system, terminal location and capacity, and wood bartering between companies and/or organizations. In tactical planning we consider decisions on catchment areas, destination of supply points and potential back-haulage routes. The system uses a GIS-based map user-interface. Two important modules in the system are the new Swedish road database and an optimization module consisting of a suite of models and methods. The development has included several organizations and forest companies. We discuss two case studies at participating companies that illustrate the usage of the system.

EN :

This study demonstrates the use of an Excel program "Routechaser" to assess the effects of tract location, vehicle operating parameters, operating costs and other physical and economic inputs on the costs of transporting wood products from roadside to mill.  The application chosen, a comparison of the effects of trucking costs from four tracts in Oktibbeha County, Mississippi, to eight markets, demonstrates that for forestry, as for any other real estate, value is a function of location.  This is especially true if forest management is directed toward lower valued commodity products.  Trucking costs were most restrictive on pulpwood, essentially eliminating many markets for several of the tracts.  Trucking costs eliminated one market for all quadrants, another market for three, and three markets for one quadrant each. 

EN :

In this field study, data were collected to determine power requirements required by a trailing site preparation plow and the magnitudes of dynamic forces experienced by a plow during normal operation and during impact with stumps or other obstructions. Drawbar pull data were collected from five different tillage treatments on a recently harvested loblolly pine (Pinus taeda) site in central Alabama. The five treatments were: 1) a coulter, ripping shank, and four bedding disks; 2) a coulter, ripping shank, and two bedding disks; 3) a coulter and ripping shank; 4) a coulter alone; and 5) a ripping shank alone. A 330 kN [75 000 lb] capacity tension load cell was used to measure the drawbar load, a GPS receiver recorded tractor speed, four direct current displacement transducers (DCDT's) monitored the depth of the disks, and two optical tachometers measured the speed of the tractor's front and rear drive shafts. Each treatment produced significantly different drawbar loads (to alpha levels less than 0.001). The resulting mean loads were 46.0 kN [10 300 lb], 33.5 kN [7530 lb], 31.5 kN [7080 lb], 15.8 kN [3560 lb], and 43.4 kN [9760 lb] for treatments one through five, respectively. Maximum recorded drawbar load during a collision with a stump was 338.9 kN [76 188 lb].

EN :

We developed a forest road design model that simultaneously optimizes horizontal and vertical alignments of forest roads using a high resolution Digital Elevation Model (DEM). Once an initial horizontal alignment is established by locating a series of intersection points, the model generates alternative horizontal and vertical alignments and cross sections along the road prism. The model also estimates earthwork volume and construction and maintenance costs for given road alignments and their spatial locations. The model then optimizes road alignments based on construction and maintenance costs using Tabu Search, one of the modern heuristic techniques.

The model was applied to a part of Capitol Forest in Washington State, USA, where a high resolution DEM derived from LiDAR (Light Detection and Ranging) data was available. First, the program generated an initial horizontal alignment with the length of 827m and five horizontal curves based on manually selected intersection points. Then, the vertical alignment was optimized based on the initial horizontal alignment, which resulted in a total cost of $50,814, considering construction and maintenance costs. The optimized forest road alignment, whose horizontal and vertical alignments were simultaneously optimized during the search process, reduced the total cost and the road length by 36% and 19% compared to the initial horizontal alignment, respectively.

EN :

Structural changes in the Swedish forest products sector have resulted in increased round wood consumption per mill. Increased consumption volumes result in increased round wood transport distances and transport output (m³·km). At the same time, the coordination of transport services is being taken over by transport organizations of increasing size. New technological developments combined with organizational innovations have made linking between transport service providers easier. This has lead to the opportunity to offer different services through networking and diversify service levels for different customers (service divergence).

This study examines the service divergence potential of round wood transport in Sweden. The goal of the study is to develop a better understanding of customer demands and service complexity. This study is based on the interview results of 20 transport service providers and buyers in the Swedish forest sector. The results presented concern three main themes: transport service goals, decisions and decision support processes. The study reports the rankings of responses as well as their correlations in order to group them into a goal-decision-decision support hierarchy. The rankings and correlations are used to suggest a customer service matrix for round wood transport. The interview also included a fourth theme describing current problems with planning and control. The responses of this final theme are related to the different parts of the hierarchy in order to identify impediments to service divergence.

EN :

Forest harvesting with animals is a labor-intensive operation. It is expensive to use machines on smaller woodlots, which require frequent moves if mechanically logged. So, small logging systems using animals may be more cost effective. In this study, work sampling was used for five animal logging operations in Alabama to measure productive and non-productive time elements to determine utilization with respect to operators, functions (felling and processing of trees, skidding, loading, and forwarding of logs), animals, and machines. Cost of log production was calculated from the figures reported by owners and the crew members. Average utilization of crew was 58 percent, animals (horses and mules) were utilized only 22 percent and the machines were utilized from 5 to 74 percent of scheduled time. Average cost of log production per m3 was $11.28. There appears to be an opportunity to reduce cost of log production by coordinating functions, increasing scheduled work hours, utilization of machines and animals, and reducing labor cost.