Volume 20, numéro 2, july 2009

EN :

Previous studies of harvester measurement accuracy assumed traditional manual log measurements were accurate and represented true log dimensions, which relies heavily on the assumption that logs are regular in shape. The objective of this study was to quantify the level of variability in manual log measurements and consider its impact on harvester calibration and accuracy assessments. Log length was measured along the top and each side and small-end diameter with callipers, a diameter tape, and a steel ruler in two radiata pine stands near Mt. Gam-bier in Southern Australia. Observed variability in manual log measurements was sufficient to affect harvester accuracy studies and calibration. Length variability on different sides of a log occurs mainly from non-square log ends. Differences due to observer were minor.Diameter measurement variability occurs mainly from the effect of stem eccentricity on each instrument, which is dependent on its number of stem contact points. Callipers have fewer contact points than a diameter tape and hence more variability. This variability was evident in comparisons between observers and instruments.

Harvester accuracy studies need to minimize manual measurement variability to identify harvester measurement errors. Length should be measured on the same side measured by the harvester. Diameter should be measured with a diameter tape in preference to callipers as they have greater stem contact and less variability.

Harvester calibration needs to minimize manual and harvester measurement variability to identify harvester measurement bias with the least number of logs to minimize the time required for these activities. In addition to the above suggestions relating to harvester accuracy study measurements, logs selected for calibration must be the most uniform in shape available to highlight harvester measurement biases.

EN :

This research quantified the equipment productivity relationships between piece size and terrain conditions for mechanized harvesting operations in native forest re-growth thinning. In addition, the economic gains or losses of adding a feller buncher to a cut-to-length (CTL) harvesting system were quantified. Study results indicate that although the use of a feller buncher working in combination with two processors is more productive than the use of a harvester-processor (single-grip harvester) working alone the high cost per tonne of this harvesting system means that its use is not recommended in areas with moderately steep terrain and small tree diameter. The differential in costs obtained between the two harvesting systems (feller buncher and two processors vs. one harvester-processor) on moderately steep and gentle terrain was approximately AUD$5/tonne and AUD$2/tonne, respectively, for an average tree diameter of 19 cm. Regression models developed from the study showed that diameter at breast height accounted for more than 85 percent of the variance in productivity of the machines and, therefore, represented the main driver of productivity and cost per tonne of the harvesting systems in all of the scenarios studied.

EN :

An optimal tree stem bucking system was developed for central Appalachian hardwood species using three-dimensional (3D) modeling techniques. ActiveX Data Objects were implemented via MS Visual C++/OpenGL to manipulate tree data which were supported by a backend relational data model with five data entity types for stems, grades and prices, logs, defects, and stem shapes. A network analysis algorithm was employed to achieve the optimal bucking solution with four different alternative stage intervals under the bucking by value principle. A total of 264 tree stems were measured in the field including stem dimensions, defects, sweep, and the manual bucking solution of each stem. Results when using the 3D optimal bucking system suggest that compared to manual bucking the total log value and volume gain from each tree stem could be increased on average by 31 to 38 percent and 16 to 17 percent, respectively. Results also show the individual tree stem utilization rate could be increased by 10 to 11 percent. The optimal bucking system developed can be used as a training tool on desktop PCs and can also be installed on field PCs to aid field buckers and operators of sawbucks. The 3D bucking optimization system developed in this research should be valuable to operators in the central Appalachian region due to the variability in tree stems and species of hardwoods.

EN :

The application, effectiveness, and compliance of forestry best management practices (BMPs) were assessed based on 33 randomly selected sites with streamside management zones (SMZs) in West Virginia. Application of BMPs was assessed based upon the methods and techniques of applying the BMP, while compliance was assessed based on the presence of required BMPs. Effectiveness was determined based upon the durability and longevity of an applied BMP. A series of 12 checklists were used to examine 29 BMPs on haul roads, skid trails, landings, and in SMZs. Spatial data, soil, stream type, and population density were also collected for the sites to identify how these spatial attributes affect BMP application, effectiveness, and compliance. Results indicated that higher levels of application, effectiveness, and compliance were found on sites with either intermittent or ephemeral streams,wider SMZs,or low soil moisture index; no significant differences were presented in BMP application, effectiveness, and compliance among stream type, SMZ width, soil series, moisture index, and population category. Road and landing layouts located outside of high water cumulative flow areas also contributed to higher rates of BMP application, effectiveness, and compliance, which substantiated the importance of pre-harvest planning.

EN :

Most mechanical forest fuel reduction treatments prescribed to extract biomass are performed with existing or modified conventional logging equipment. Treatments that commonly harvest small, non-merchantable trees are often combined with or integrated into commercial thinning operations. Only a limited amount of literature has quantified harvesting system feasibility or environmental effects from such operations. The extra stand travel required to fell and extract small trees may lead to additional soil disturbance. The objective of this study was to assess soil disturbance from an integrated forest harvesting/mechanical forest fuel reduction operation in southwest Oregon, USA. The study was conducted in a fuel reduction thinning of a densely stocked 8.1-hectare (20-acre) mixed conifer stand on gentle terrain. A tracked, swing-boom feller-buncher and two rubber-tired, grapple skidders were used for felling and extracting both non-merchantable and merchantable trees. Visually classified soil disturbance, along with penetration resistance estimates were recorded pre- and post harvesting. Results indicate that the operation did not contribute to either statistically or biologically significant soil disturbance effects, based on an a priori biological reference threshold of 3,000 kPa. A history of multiple harvest entries, low soil moisture, and high initial soil strength conditions contributed to the lack of significant effects. This investigation will aid forest managers in decision making concerning expected soil disturbance effects when prescribing integrated harvesting systems for forest fuel reduction treatments.