There has always been a requirement for accurate maps to assist the decision making processes in the establishment, tending, and harvesting of forests. This need is emphasized at the present time with the advent and implementation of technologies such as GPS and GIS that have the capability to provide and utilise, information of high spatial accuracy. John Firth,1 Rod Brownlie,1 and Ward Carson,2 here emphasize the need for a solid foundation on which to base sound forest harvesting practices.
In our role as photogrammetrists and foresters, we have carried out numerous mapping projects for several large forestry companies around the world. This has involved not only the production of new maps but also auditing the areal data bases of the forestry companies, often as part of a privatisation process.
We have evaluated over one half million hectares of mapped forest in the last 15 years. A common trend observed throughout many of these evaluations has been for the maps to relatively accurately portray the extent of the resource and yet to be somewhat less accurate when geo-locating the forest stand boundaries.
Analysis of the identified map discrepancies has shown that the area of forest stands had usually been measured to an accuracy of better than _ 5%. The same analysis also showed that the boundaries of the stands were often laterally displaced by up to several decametres with respect to their correct position. The references for these assessments were maps produced, of the same stands, using a precision analytical stereoplotter.
Spatial and/or locational errors of these magnitudes can affect the forest manager's estimates of timber volume, an important aspect of forest value. Similarly, inaccurate maps can have a negative impact on the cost effectiveness of managing forest operations. Accurate areas are essential for the equitable negotiation of contracts with silvicultural operators while harvest planners require accurate spatial and topographical information in order to avoid costly errors resulting from the incorrect location of logging roads and harvesting machinery.
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The mapping errors identified above can often be attributed to an approach commonly taken when producing forest maps. Generally an accurate base-map is first produced from metric aerial photographs using a photogrammetric stereoplotter. Errors are introduced when these maps are progressively updated, using the less precise method of a simple optical/mechanical transfer instrument. These instruments enable the required changes to be transferred from new aerial photographs to the map. However, unlike a stereoplotter, these relatively simple instruments do not fully take into account distortions in the photograph due to relief displacement, tip/tilt of the camera, and lens distortion. While the transfer instruments have served well for many years, cartographers are now evaluating new technologies which overcome their inherent limitations.
High definition aerial photography will continue to be the medium best suited for base-map creation and the map-revision process for some years to come. However, the approach taken to carry out map revision in the future is likely to be based on the use of relatively inexpensive, computer-based mapping tools. These utilise photogrammetric principles, in combination with a digital terrain model, to correct for photographic image displacements. They also offer the possibility of providing an ortho-image backdrop to the traditional line work map.
Implementation of modern computer-based mapping tools will lead to improved spatial precision of forest maps with an increase in the confidence with which the resource manager can approach the decision making process.
1 New Zealand Forest Research Institute Ltd, Private Bag 3020, Rotorua, New Zealand.
2 Forest Photogrammetry Lab, College of Forestry, Oregon State University, Corvallis, OR, USA
Field studies on three road construction sites in the Alps of Austria examined the construction of road by use of hydraulic excavators and advanced rock drilling and blasting techniques. The work and time studies were by Norbert Winkler, FAO, in cooperation with Josef Egger, Federal Forest Service of Salzburg.
The results of this case study show that the environmentally sensitive techniques applied to the three road projects are superior to road construction by the traditional use of bulldozers on steep slopes. There are short-term economic benefits from use of bulldozers in forest road construction. But in the long-term, dozer construction in mountainous terrain is likely to create considerable environmental damage. The scale of damage increases as side slopes increase.
Some advantages of road construction by means of hydraulic excavator and advanced drilling and blasting techniques are listed here.
Advantages of construction by excavator
Subgrade width can be kept to the absolute minimum determined by safety and anticipated use because the excavator operates from a fixed position or by movement parallel to the road centreline.
Excellent control in the placement of excavated material as the excavator operates by digging, swinging and depositing material with accuracy and care.
Excavated material can be separated and temporarily stockpiled by the excavator in anticipation of its best use in building the road.
Total construction width is minimized since subgrade width and length of fill slope are minimized.
The use of a hydraulic hammer that can be easily attached to the excavator results in less need for blasting and the resulting collateral blast related damage.
Damage to stands along the road is reduced because excavator operators can swing, dig, and place material with accuracy.
Drainage and erosion control can be installed immediately and function satisfactorily during the entire project.
The cost of excavation and embankment at the three study sites ranged from US$10 to US$96 per metre.
For more information see Publications, FAO Forest Harvesting Case Study 10.
Fill construction is one of the most important tasks in proper road construction. The separated excavation materials can be seen piled on the hillside.
We see that hydraulic excavators are very useful for forest road construction and maintenance. It may be an economic advantage to also use the construction excavator as a forest harvesting machine. The opportunity to increase the productive operating time of an expensive machine is always attractive. The hydraulic excavator is used worldwide for a wide variety of forest harvesting tasks.
Large volumes of wood are moved from the stump to roadside by an environmentally friendly and cost effective loader logging system. "Hoe-chucking" is a vivid appellation used in Canada.
A variety of processing heads are manufactured for attachment to hydraulic excavators.
A wide selection of harvester and feller-buncher heads is available throughout the world. The harvester pictured here is designed for thinning operations in small timber stands. It was described in a recent issue of "Schweizer Holzzeitung" No. 40 (Swiss Timber Journal). The maximum felling diameter of this particular harvester, which weighs 365 kg, is 410 mm.
Hydraulic excavator with a harvester head attached.
SkogForsk has been studying Central Tyre Inflation (CTI) equipped roundwood haulage rigs since 1993. It is estimated that the closure of roads during the spring thaw costs the Swedish forest industry US$52 million a year in increased storage costs and resultant quality losses in the timber.
Paul Granlund and Gert Andersson reported on the operation of a CTI equipped rig on roads affected by the spring thaw compared with a conventional rig operating in the same conditions.
Trials on a forest road in the late spring found that ruts had become so deep after six passes by the conventional rig that there was a serious risk of the vehicle becoming bogged down. In contrast, the rig with reduced tyre pressures could make 30 passes without being in danger of becoming bogged down. A 40 tonne payload was transported on a road that would normally have been closed to traffic during the thaw.
The collective experience of studies in North America and in Sweden show CTI to be useful for increasing access to road networks. CTI reduces ground pressure, improves mobility, and allows higher tractive force to be developed. See SkogForsk, Resultat Nr 2 1998; FERIC, SR-123, 1997, A. Bradley; and VTP, USDA Forest Service, 1995.
Peter Hall, Forest Engineering Researcher, Liro Ltd. studied harvesting systems that separate the extraction and processing of logs into two stages. Tree length material (up to 35 m) is brought to a minimum sized landing by cable or tractor equipment and loaded on off-highway trucks. The loaded trucks travel up to 5 km to a central processing landing where the trees are processed into optimal length logs. Hauler production gains of 25% to 50% have been observed. Overall system productivity gains are substantial. Other benefits include reduced soil disturbance, less productive land lost to earthworks, improved worker safety, and in some cases reduced processing residue problems.
For more information contact Liro Ltd., Rotorua, New Zealand, email: info or firstname.lastname@example.org
Mike Jurvélius has compiled a case study based on experiences with simple, labor intensive harvesting of timber from tree plantations in the southern Philippines.
Considerable effort was made, beginning in the mid 1970s, to develop and promote appropriate wood harvesting and transport technologies in the Philippines. These technologies did not gain widespread acceptance until the 1990s. Careful efforts were required to ensure that the developed technologies were in fact appropriate and that relevant training and education programs were offered.
Many people believed it was not possible to supply the large volumes of wood required by modern forest industries using labor intensive manual and animal systems. Others discriminated against such technologies, assuming them to be backward and inappropriate for modern forestry operations. The recent experience in the southern Philippines has caused a reassessment of such thinking. The experience of harvesting large volumes (250 000 m3/yr.) of plantation grown wood clearly demonstrates the potential advantages of labor intensive methods under certain socio-economic conditions.. These methods are often less costly and less damaging to the environment than more mechanized harvesting. They provide employment for large numbers of people and are less dependent on fossil fuels. The methods studied included handsaw and ax use, manual loading, and carabao skidding. For additional information see Publications, FAO Forest Harvesting Case Study 9.
Previous articles in the Forest Harvesting Bulletin about harvesting impacts in Brazil, Congo, and Indonesia stimulated D. I. Nicholson to share impact data from Australia. He and M. G. Keys authored a paper reporting on twelve studies of harvest impacts in both virgin and recut forests. Some more stringent logging controls were introduced in these forests in 1982. These studies suggest a marked improvement after 1982 in measured soil and tree damages. For example, total infrastructure surface area (snig track) fell from 15% to 9%. The area in severe soil disturbance classes fell by 75%. For the paper or more information contact D. I. Nicholson, 7 Maher Street, Atherton Q 49983, Australia
Field studies by Norbert Winkler, FAO, Carlos Alberto Guerreiro, João Heitor Faraco Jr., João Cruz Rodrigues, and Tim van Eldik, Mil Madeireira Itacoatiara Ltd. examined harvest practices in Amazonas, Brazil. The Precious Woods Ltd. project area comprises 80 900 ha.
The results of this case-study show that environmentally sound forest harvesting, as applied by Precious Woods on this project, is superior to timber harvesting in the traditional way of the Amazon region in Brazil. The estimated short term cost per cubic metre for the traditional logging system was about 1% less than the environmentally sensitive harvesting system. Given the accuracy of the estimate this difference is probably not significant. However there definitely are significant environmental, social, and long term economic advantages to harvesting with the newer practices.
Some of the advantages of the environmentally sensitive forest harvesting system are as follows:
Some long term economic advantages
The volume of residual commercial trees that can be expected to be harvested in the next harvesting cycle increased by 100%.
The number of the residual commercial trees in an acceptable condition with little or no damage increased by 50%.
Timber losses amounted to 3.9% of the utilisable stem volume at the felling site, about half the rate with the traditional system.
Sustainable forest management of the project area provides an assured timber supply to the company-owned sawmill.
Some social advantages
Company housing with adequate standards of comfort and sanitation are provided for the employees.
Stable employment throughout the year is available to the employees.
The frequency and severity of accidents associated with harvesting operations is reduced by well-trained, competent personnel, outfitted with appropriate safety gear, and using properly maintained equipment.
Some environmental advantages
About 1/3 of the forest area is purposely set aside as preservation forest area.
The area affected by forest roads and trails is reduced by about 400%
Soil disturbance associated with soil compaction is restricted to the areas used for permanent forest infrastructure facilities
Rotten trees are not felled, but preserved as shade and seed trees in order to diminish environmental impacts
At least 20% of the volume of every tree species remains unharvested to assure the continued existence of all tree species.
Permanent sample plots established before harvesting enable monitoring of stand development. Feedback about the quality of harvesting operations and silvicultural treatments will advance the knowledge of tropical rainforest ecosystems.
The great superiority of the environmentally sound forest harvesting system in producing tropical forest products is obvious. Use of the principles of sustainable forest management benefits the environment and the population as a whole.
For more information see Publications, FAO Forest Harvesting Case Study 8.
Wheeled skidder equipped with grapple remains on skid trail at all times.
Firth, Brownlie, and Carson discussed the need for accuracy in forest mapping on page one of this Bulletin. SkogForsk has studied and quantified the value of accuracy in measuring logs.
There is a growing need for logging organizations to merchandise sawlogs to specified dimensions that are better suited to the sawmill production. This means that the function and accuracy of measuring equipment must also meet tighter requirements. The measuring data consist of length and diameter measurements. The quality of the measured values from the sensors has a decisive influence on whether the logs meet the specified dimensions, which is critical to the effectiveness of the merchandising system.
Calculations have shown that improved diameter measurement could increase revenue per cubic metre by between US$0.06 and US$0.28 per millimetre of reduction in the standard deviation. In terms of harvester output, this corresponds to an annual saving of US$2500 to US$11500 per millimetre of standard deviation improvement.
A remote, noncontacting test measuring frame has been designed for single-grip harvesters. Field tests compared the performance of the remote measuring frame with that of the callipered values and current merchandising system. The results showed that 75% of the logs fell within a range of ± 4 mm of the peak value measured by the callipers. This still falls short of the target (90%) but is better than the mean value (67%) returned by limbing knives equipped with a potentiometer-type diameter sensor.
More work is required to develop this measuring system but it is believed that 85-90% of measured log diameters will be in the range of _ 4 mm. The estimated cost of a functional, remote diameter measuring system for a harvester will be approximately US$20 000 per unit.
This particular effort dealt with measurements by highly mechanized harvesting machines. However, notice that the calculation for the value of accuracy is independent of the mechanism used for the measurements. The same value relationship would apply for measurements made by a worker with a measuring tape. How many millimetres of improvement are available with the typical manual measurement system? For more information contact SkogForsk, S-751 83 Uppsala, Sweden, www.skogforsk.se.
FERIC is also studying log-measuring accuracy. Glen Young, Björn Andersson, and Peter Dyson compared log-recovery values in a study of four log-manufacturing methods on Vancouver Island. A single-grip harvester, a processor at roadside, a manual fell and buck system, and the theoretical values predicted from pencil bucking using both a grader and a landing bucker were studied. They found the overall net value recovery for all bucking systems was significantly lower than the optimum predicted by the grader and bucker. Both of the mechanized systems recovered less volume and value than the manual systems. The main causes for value loss in the mechanical systems were problems with obtaining longer prime lengths and difficulty in accurately sensing diameters consistently along the log.
FERIC has started comparing the length of logs actually produced to the length indicated by the equipment sensors and computer. This study is being conducted throughout western Canada.
Research studies were conducted on forest land owned and managed by the forest directorate of Kastamonu region in Turkey. A series of detailed yarding studies were conducted to define yarding production by both a skyline operation and a tractor operation. Variables influencing logging production such as yarding distance and pieces per turn were measured. Operations were timed to the nearest 1/100th of a minute.
The production rates were similar for both the skyline and tractor systems, about 6 m3/hour.
Average stand characteristics
Pinus Sylvestris L.
Direction of slope
Advantages of logging on snow in winter:
· Natural regeneration under the snow layer is not harmed.
· Soil is protected from disturbance, compaction, and erosion.
· Winter temperature and moisture protect timber quality from fungal and insect damage.
· Labour is easier to obtain because of reduced farm work during the winter.
· Local villagers are provided year-round work.
· Winter harvested timber commands a higher selling price. For example, observed prices for pine logs sold in April have been about 30% more than prices for the same class of log sold in November.
Disadvantages of logging on snow in winter:
· Daily productivity is reduced by shorter days and more difficult conditions.
· The accident risk is very high because:
· the ground is frozen and slippery;
· snow on the canopy of trees changes the normal distribution of forces;
· snow and icicles fall on workers.
· Special protective equipment is required.
For more information contact Metin Tunay, Faculty of Forestry, Karaelmas University, Bartin Orman Fakültesi, Bartin, Turkey.
Trees up to 500 years old were harvested between 1850 and 1930. A normal part of harvesting these forests included rafting the logs on Lake Superior. Many of the slow grown logs sank in the lake. The annual growth rings on these "sinkers" can be up to 20 rings per cm. The lake's cold water temperatures and low oxygen content have helped maintain the logs in good condition. The logs are now being salvaged by SCUBA divers and turned into high value products such as flooring, paneling, furniture, and musical instruments by Superior Water-Logged Lumber Co. See www.oldlogs.com. News from Wood Technology, October 1997, vol. 124, no.8.
A study by D. Dobrowolska, D. Farfal, and W. Józefaciukowa assessed the root damage caused by timber harvesting in late thinnings of Scots pine (Pinus sylvestris L.). Two harvesting methods were applied (whole stem and shortwood) using five felling/skidding combinations: 1) chainsaw and horse, 2) chainsaw and skidder, 3) chainsaw and forwarder, 4) single grip harvester and skidder, 5) single grip harvester and forwarder.
Three 60 year old stands were included in the study. Two categories of root damage were reported: slight injuries in which the bark above the roots was frayed or broken to the sap wood and severe injuries in which the bark was scraped of and the wood damaged enough to cause root decline. Severe root damage was 0.8% for the shortwood method and 3.4% for the whole stem method.
In Prace Instytutu Badawczego Lesnictwa (1996) No. 819-824, 37-44. Raszyn, Poland.
The Wageningen Agricultural University (WAU) in the Netherlands offers a 17 month MSc course in Tropical Forestry. The program begins every year in September and offers two specializations: Social Forestry and Silviculture & Forest Ecology. Applicants should have a BSc. in forestry (or equivalent), fluency in English, and preferably working experience. Application for the 1999-2000 course must be made before November 15, 1998.
The Social Forestry specialization provides opportunities to focus on social, economical, extension and policy aspects of the use of trees and forests by rural people. The Silviculture & Forest Ecology specialization provides opportunities to focus on ecology, silvicultural systems based on natural regeneration, and timber production. Other items can also be chosen, e.g. agroforestry. Any individual program consists of a thesis, research methodology and thesis oriented courses. Subject to approval of the Board of Examiners thesis research might be conducted within the framework of ongoing development projects in the country of the applicant.
In general, students should arrange their own funding. The WAU offers a very limited number of fellowships for outstanding students. For more information please contact: Department of Forestry, MSc course Director, Frits J. Staudt P.O. Box 342, 6700 AH Wageningen, The Netherlands.
Fax: +31 317 483542, email: email@example.com
The International Institute for Aerospace Survey and Earth Sciences (ITC) offers MSc degrees to assist developing countries with remote sensing and geographical information. Contact: ITC Student Registration, P.O. Box 6, 7500 AA Enschede, The Netherlands. http://www.itc.nl.
The Forest Engineering Research Institute of Canada, FERIC, studied a novel rail transport system. The ECORAIL system offers potential advantages in terms of costs, year-round hauling, and environment impacts particularly for transportation distances between 300 and 1000 km.
The ECORAIL transportation system comprises four components:
· The control unit, which is positioned at the front of the train, contains the computers and control devices required to manage the train.
· The 500-kW engines are inserted into the train as required by topography, track conditions, and payloads.
· The bogies consist of a chassis with two railroad axles and a fifth wheel at each end.
The truck trailers must meet size and structural criteria. The trailers are supported at their ends rather than on their axles. The study provides information for evaluating the potential for this mode of transportation. It provides cost calculation elements and lists some operational limitations and advantages.
See FERIC Technical Note TN-253, 8 p, The ECORAIL System for Transporting Chip Vans by Rail, by Yves Provencher, 1997.
Train assembly steps for the ECORAIL Road-Rail-Road system