Payload development in truck hauling of tree sections was studied, using production statistics from central Sweden. An increase of payload weights over four years was observed.
Factors influencing productivity may be divided into groups connected to a) technology, b) human skills, c) work object properties and d) working conditions. Apart from varying weather and seasonal climactic change, no productivity change or development could be observed associated with technology, work object properties or working conditions during the course of the 49-month study. The operators studied were all experienced roundwood hauling contractors, but had no previous experience with tree section hauling. Their experience of the work studied and on the equipment increased during the study.
Under the stable conditions of this study, the most important factors influencing payload variation are increased operator skill and varying weather and climate. Meteorological data explained more than 70 per cent of the variation but a logarithmic increase of payloads along with a decreasing sensitivity to weather conditions remained unexplained. Hypothetically, this is accredited to growing operator skill including an increased ability to judge and compensate for varying characteristics of tree sections handled. If so, the learning phase might be longer than generally assumed. To shorten this low-productivity period is an important aim for vocational training for workers and contractors in forestry. Some methodological problems connected with the interpretation of production studies are also discussed.
Quantitative Analysis of Fragmented Landscape Patterns Resulting from Timber Harvesting Practices in Kyoto University Forests
This paper presents the use of a set of spatial statistics to quantify the forest landscape pattern caused by the patchwork of timber harvesting and the subsequent coniferous plantations made over a 60-year period (1921-1981) in the natural forests of Kyoto University Forests. Aerial photography and orthophotography were used to analyze spatial patterns of forest cover changes at patch level between 1974 and 1996. Base maps of forest pattern were digitized in raster format using four dominant forest cover types in the study area The total number of digitized patches for 1974 and 1996 were 435 and 453, respectively. Four groups of indices were employed to quantify landscape heterogeneity and pattern for each of the two years: (1) patch size; (2) patch abundance; (3) patch shape; and (4) patch spacing. Patch abundance and patch spacing measures provided considerable information on major patterns of forest landscape dynamics over time. Patch size and shape indices contributed information on specific characteristics of the individual patches and may be useful for applications designed to study specific interior and edge habitats or for the prescription of forest cutting patterns and/or cutting-unit size. The net loss of forest covers that occurred during 60-year period trends to be balanced primarily by regeneration of areas cut before 1943 and secondarily by plantation of areas cut before 1965.
Tree damage in a one-grip harvester operation was assessed by observing the number of contacts with standing trees and damage resulting from these contacts. The processing phase for a single tree was called a cycle. On average, 19.3% (14.5 - 25.4%) of cycles involved contacts with standing trees. One third of the contact trees were removed during harvesting. Of the struck trees left standing, 28.2 % were damaged. The probability of contact damage was 1.5 times higher in the summer than in other seasons. Mean damage percentage in the study stands was 3.4 ( range 0.0 - 8.6%).
Contacts with standing trees were explained by machine operator, stem volume of processed tree and the number of trees on the working area. The probability of damage resulting from contact was explained by harvesting season and size of processed tree. A model was developed to predict tree damage. The model consisted of a contact model and a damage model formulated using logistic regression. The tree damage model and the productivity models can be used, for example, in comparing different thinning regimes in model stands.
The operator had considerable influence on both the harvesting quality and productivity, and there was a large variation between machine operators. High productivity and a good silvicultural result were highly correlated.
Timber Harvester Perceptions of Costs and Benefits from Applying Water Quality BMPs in North-central USA
Charles R. Blinn, Anne-Marie Alden et Paul V. Ellefson
Forestry Best Management Practices (BMPs) prevent or minimize the impact of forestry operations on water quality. Relatively little is known about the net financial effect to timber harvesters from applying water quality BMPs. A survey of Minnesota timber harvesters found them to be well acquainted and willing to comply with the states water quality BMP program. Although the BMP program was officially implemented in 1990, many practices were apparently being widely applied prior to the programs initiation. These practices were probably already providing important financial benefits to timber harvesters. From 1990 through 1994, however, most timber harvesters (75 percent) reported increased costs associated with applying 40 individual water quality BMPs. Only 16 percent reported financial gains from applying the individual BMPs. When looking at the net financial effect across all 40 BMPs studied, 87 percent reported a net increase in costs from applying those practices. A number of recommendations are provided to assist BMP policy makers, program designers, and educators.
Chris B. LeDoux et Neil K. Huyler
We compared production rates, operating costs, and break-even points (BEP) for small and large cut-to-length (CTL) harvesting systems operating at several machine utilization rates (MUR) in mixed hardwood and softwood stands in Vermont. The small CTL harvester produced 11.08 m3 [391.4 ft3] per productive machine hour (PMH) compared to 14.83 m3 [523.80 ft3] per PMH for the large harvester. The impact of average tree size (volume) on cost was substantial but similar for both CTL systems. At a fixed stump-to-landing logging cost of about $14.12/m3 or [$0.40/ft3], the BEP tree size was 0.14 m3 [5.0 ft3] for the small harvester and 0.26 m3 [9.33 ft3] for the large system at the 85 percent MUR. At an MUR of 70 and 85 percent, the processing cost for trees that averaged 0.08 m3 [3.0ft3] was $22.19 and $18.28/m3 [$0.6285 and $0.5176/ft3], respectively, for the small CTL harvester. Results were similar for the large harvester. Either CTL system would be effective in helping managers meet forest management goals in eastern hardwood stands.
John Klepac, Bryce Stokes et Joe Roberson
Evaluation of skidder productivity and costs among 30.5L-32 (78-cm), 67x34.00-25 (86-cm), and 66x43.00-25 (109-cm) size tires under wet conditions was conducted in a clearcut harvest during the Spring of 1998 on an Upper Coastal Plain site in southeast Alabama. There was not a significant difference in adjusted mean whole-tree skidder production among the three tire sizes at the 0.05 level. Adjusted mean whole-tree skidder production for the 78-cm, 86-cm, and 109-cm tires was 32.7, 35.8, and 32.9 green tonnes per Productive Machine Hour (PMH), respectively. Total whole-tree skidding costs were $1.96, $1.80, and $1.97 per green tonne for the 78-cm, 86-cm, and 109-cm tires, respectively.
Audrey A. Martin, Nicholas M. Holden, Philip M. Owende et Shane M. Ward
The purpose of this study was to evaluate differential global positioning system (DGPS) positional accuracy on Irish forest roads with typical peripheral canopies. The peripheral canopy obstruction at 20 forest road sites in Roundwood State Forest, was determined using a hand-held clinometer and magnetic compass. This simple field technique permitted quantification of the canopy obstruction using graphical means and resulted in a graphical skyplot of each site. The equipment, one Trimble ProXRS DGPS unit and two Trimble 4000SSi units permitted determination of the DGPS accuracy (average of 2.9 m) and precision (average of 2.1 m) with a range of peripheral canopies. DGPS performance was quantified in terms of the average absolute error in positional dilution of precision (PDOP) (DPDOP = 1.6). The relationship between DPDOP and percentage of open sky was found to be statistically significant (r = 0.706, r = 0.001). Statistical analysis also indicated a strong relationship between relative precision and DPDOP (r = 0.796, r = 0.000). Satellite constellation in the measurement period was not the sole factor affecting DGPS useability. Three distinct classes of peripheral obstruction at road sites were defined (Class I: 100-66 %; Class II: 65-33 %; Class III: 32-0 % obstruction) and it was found that both DGPS accuracy (3.70 m, 3.23 m, 1.91 m, respectively) and precision (4.10 m, 2.43 m, 0.83 m, respectively) improved with decreasing peripheral obstruction. These classes may be used as a means of predicting signal attenuation which might be expected under particular forest canopy conditions elsewhere.
Erik S. Drews, Bruce R. Hartsough, James A. Doyal et Loren D. Kellogg
Two harvesting systems were compared for reducing fuel loadings in overstocked conifer stands in eastern Oregon; forest managers also set a high priority on minimizing soil disturbance. Both employed cut-to-length (CTL) harvesters; one used a forwarder and the other a small skyline yarder. Both systems produced very similar and acceptable results in terms of fuels reduction and soil disturbance, but at different stump-to-mill costs: $46/green ton for the forwarder system versus $80/green ton for the yarder system.