|Society of American Foresters||International Society of Tropical Foresters|
Patricio Mac Donagh,
Professor Adjuncto Facultad de Ciencias Forestales,
Universidad Nacional de Misiones (UNAM)
Eldorado, Misiones, Argentina
Forest access is essential to achieve forest management goals. Access requirements are dependent on management goals, geographic location, harvest methods utilized, and other on-site factors. Roads provide essential access for the active management of forest resources. Forest management, timber removal, recreation, and fire protection, as well as other activities, are all heavily, if not totally, dependent on road access into the forest.
For society, forest roads create economic activity and provide an access for local people and thus allow them to sell their production. They also improve medical, educational, social and recreation services.
The construction and maintenance of forest roads represents an important and essential investment as a complement of forest growth. In this sense needs a careful planning with the objective of minimizing the necessary cost. Minimizing total distance of roads in the forest reduces road construction and maintenance costs, and reduces land taken out of the forest management base. Less roads means less potential for adverse effects on other natural resources.
Besides being an asset, roads are recognized as sources of erosion and sedimentation, impact wildlife and aquatic habitats, remove valuable timberland from production and require significant work and expense to build and maintain. For these reasons, an environmentally sound, economically efficient and effective road management program must be utilized on forest lands.
Building and maintaining roads is controversial, however, because of the kinds of uses they enable, concerns about their short- and long-term effects on the environment, and the value that society now places on unroaded wilderness.
The forest road system should provide efficient, effective access that facilitates securing the greatest permanent value on forestry lands and obtaining the greatest benefit. The forest road system should be managed actively, not passively. Roads are designed, constructed and maintained in the most cost-efficient manner, while providing a high level of protection to other natural resources. The standard for roads in the forest is a suitable match for the terrain and type of access needed. The roads are effectively maintained to retain their longevity and to prevent adverse effects to natural resources. Unneeded roads are closed or vacated and, where appropriate, the land they occupied is returned to active forest management.
The investment level in forest roads will depend on the harvesting systems, the road standard requirements, the construction and maintenance costs, and the stand volume of each particular situation.
In many countries, the forest road network planning is a part of land planning. When a forest road system is planned, the following issues should be taken in account:
1. Forest type (stand volume, species composition)
2. Volume flow
3. Landscape, terrain, slope, soil type
4. Climate, rainy seasons, and periods of road utilization
5. Environmental requirements, impacts, restrictions
6. Infrastructure, existing roads, services
7. Non-timber forest products and services
8. Government policy and regulations.
Forest Road Classification
According with Kantola and Harstela (1991) a standard forest road classification could be as follows:
1. Skid trails, those places in the forest used to move the stem or the logs from the stumpage to temporary roads or landings areas.
A fairly flat area with little soil movement to build the site is required, with usually only bushes and some trees removed.
2. Temporary roads are roads constructed for tractor transit from the skid trails to landing areas or to secondary roads. Some soil movement is needed
during construction in this case, and light machinery is often used to build it.
3. Secondary roads connect landing areas with primary roads. These roads have some traffic restrictions during rainy seasons, and are used mainly
during forest operations. Soil movement is frequent, but no asphalt or gravel is employed.
4. Primary roads, the basis of the forest road system, allow timber transportation with trucks, and are usually employed along the whole year, including
during rainfall. The standard construction costs are greater than the other roads, as required by the engineering design and construction.
Access roads, mainly public and multipurpose roads, connect cities and small towns.
Another classifications could be made according to technical and traffic parameters as follows in Table 1.
Road and Loging Cost Interaction
Road and logging costs are closely related, and are usually expressed as total cost figure. This means that the optimum distance between two forest roads, in meters, will provide the minimum total cost, considering the sum of the cost per meter of construction and maintenance of a forest road, plus the logging cost related to the average distance of transportation (Figures 1, 2 and 3). This type of analysis is specific for each type of road cost, and each type of skidder or tractor. An empirical example (Table 2) is provided for example, including stand volume, because the concept is that harvested volume should pay for the expenses in road construction and maintenance.
Figures 1,2 and 3 present examples for the same plantation--eucalyptus of 215 m3 in a clearcut, and roads of $0.50 /m (temporary roads), $6.00 /m (temporary roads); and $15 /m (secondary roads).
It can be observed from figures 1 to 3, that if the quality of road is improved, the skidding distance increase, and the minimum cost is reached around 75 m between roads in the first case, around 200 m in the second case, and 275 m in the third.
Utilization of GIS (Geographical Information Systems) also is an excellent and modern tool for planning and control road construction and maintenance. In any case a combination between satellite images, aerial photograph (digital), and field measures with GPS (Global Position Systems), could be considered a technical package that provide modern on site solutions.
In conclusion, forest roads cannot be considered isolated of harvesting systems, and should be related as a function. These figures are empirical; motion time studies are recommended to find the logging yield in each situation, and adjust the optimal road network to minimize total road and harvesting cost. The principles discussed here for forest roads for timber management also apply to road building for other uses, incuding recreation, wildlife, hunting, or aesthetic enjoyment. Due the great variability in the results, any uniform generalization about the best road structure width should be avoided, and one must take the use of the roads into account. The objectives with roads will always include developing the best network possible that provides the desired level of access at the least cost while protecting the environment from adverse effects.
Dykstra, D.P., Heinrich, R., 1996. FAO Model Code of Forest Harvesting Practice. Food and Agriculture Organisation of the United Nations, Rome, 97 pp.1996.
Gucinski, Hermann; Furniss, Michael J.; Ziemer, Robert R.; Brookes, Martha H. 2001. Forest roads: a synthesis of scientific information. Gen. Tech. Rep. PNWGTR-509. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 103 p.
Kantola M. And Harstela P. 1991. Handbook for proper technologies in forest operations in developing countries. Part II. Chapter 4 Pp 35-97.
Wilbrecht 2000. Forest Engineering Roads Manual. Oregon Dept. of Forestry. State Forests Program.
17 April 2006; V #3
Posted: 3 August 2006
Updated: 22 April 2007