INTERACTION BETWEEN NETWORK OF SERVICES: FORESTRY AND WOOD HARVESTING SYSTEMS
SOME ECOLOGICAL PROBLEMS OF TIMBER HAULING BY LOG TRUCKS IN SLOVAKIA
INTERCONNECTION OF FOREST ROADS NETWORK, HARVESTING AND WOOD TRANSPORT
OPTIMIZATION OF LOAD DISTRIBUTION ON FOREST TRUCKS
TRACTION PARAMETERS OF FOUR SKIDDERS USED FOR WOOD TRANSPORTATION IN MOUNTAIN FOREST THINNING
USE OF CABLE SYSTEMS ON SOFT GROUND IN NORWAY
ROAD DEVELOPMENT AS A BASIS FOR SOUND FOREST MANAGEMENT PRACTICES UNDER CENTRAL EUROPEAN CONDITIONS
Sanzio Baldini1 and Claudio Pollini2
1 Professor, Di.S.A.F.ri, Tuscia University, Viterbo, Italy.
2 Institute for wood technology, Consiglio Nazionale delle Ricerche, Italy.
In Italy, forests cover 28.8 percent of the territory. The following table shows their repartition according to type.
|
Forest type |
Area |
|
|
Hectares |
% |
|
|
High forest |
2 178900 |
25.1 |
|
Coppice |
3 673 800 |
42.4 |
|
Plantation |
288 900 |
3.3 |
|
Small trees |
2533500 |
29.2 |
|
Total |
8 675 100 |
100.0 |
Another distribution according to steepness of terrain where forests are located is as follows:
· 35 percent with a slope inferior to 30 percent; wood harvesting is performed mainly with the help of animals or with towlines or winches equipped with tractors;· 40 percent with a slope between 31 and 60 percent; wood harvesting is mainly done with tractors equipped with winches or with skylines from roads or tracks,
· 16 percent of the forests are located on slopes ranging from 60 to 80 percent; wood harvesting is done from roads, on short distances, only with skylines.
When the steepness of the slope is over 80 percent, which means in the remaining 9 percent, wood is not harvested as it is very difficult to open roads and tracks and, apart from their high cost, these activities would also have a negative impact on the environment.
Silviculturists and users know very well the importance of forest roads to maintain and promote environmental balance through silvicultural cutting.
The achievement of a new forest development or the new management of old tracks, which are numerous in Italy, must be planned in accordance with the future exploitation pattern of the territory with the objective to realize works which can be utilized on a long-term basis. It is in this particular moment that the impact of such works on landscape and environment must be carefully taken into account. If some small wooded areas cannot be reached for example for ecological, hydro-geological or environmental reasons, this must not be viewed as a tragedy. Opening a road to reach an area located at high altitude can involve high economic and environmental costs. In this case, it is better to give up the idea of exploiting this part of the forest.
The layout must be chosen not only for silvicultural operations but also to prevent and control fire, particularly in Mediterranean countries.
Unfortunately in Italy it is difficult to talk about a forest road network because the population has never been well informed (except in a few areas) about the usefulness of these infrastructures, from both environmental or social viewpoints. Apart from this, there is no planning that takes account what has just been said. So we have, on one side, forest enterprises that develop tracks for their immediate use which will later create torrent and, on the other side, the possible intervention of justice that blocks everything. There is no planning and, as said before, nobody links these infrastructures to the areas concerned.
The high costs involved in wood exploitation, the impossibility to take action in time through roads in the case of fire outbreaks or to prevent them, all this in our country is mainly due to the lack of an appropriate forest road system.
In Italy, right now, only the northeastern regions with many high forests have recognized the usefulness of this planning in view of developing a natural exploitation of forests.
In these areas, the forest road density averages 23-25 m/ha and the density of main tracks 50-100 m/ha. These data are far above those found in central and southern Italy which average 6-15 m/ha for roads and 10-15 m/ha for tracks.
However, it is not difficult to find in certain areas a road density of 20-25 m/ha, but forests do not benefit from them because the roads run alongside the forests without crossing them.
This is a classical example of infrastructures planned by individuals who took no account of the "trinomial" road-silviculture-society.
A phenomenon that has occurred frequently during the last few years in central and southern Italy, where new forest tracks have been opened, is the increase of the number of forest fires. They are caused by the many tourists who travel through the forests by car. To limit this phenomenon, all what would need to be done would be to prevent cars from entering the forests by placing gates across the ways of access, leaving passages for pedestrians and bikes.
Harvesting methods used according to forest roads density
In forests having a maximum slope of 30 percent, wood harvesting of fuelwood or small-size wood for the paper industry is carried out with agricultural tractors with trailer. In the case of logs or full trees, the tractor is equipped with a winch.
This system allows a great flexibility to the silviculturist and does not require a high road density (10 to 20 m/ha).
Generally, temporary tracks are arranged between rows of standing trees at a distance of 60-100 m from each other.
In terrains with slopes ranging from 31 to 60 percent, the density of main roads is 25-35 m/ha. This means 60-100 m/ha of main permanent tracks. In this case, tractors equipped with winches are used to collect the wood in an upward direction from the road. However, to carry fuelwood downwards, mules or plastic log lines are used. Skylines are also used if the quantity of wood justifies their installation..
These types of equipment are also used when the road density ranges between 18 and 20 m/ha only. In this case, the length of installations can reach 650 to 700 m. For wood harvesting in the Italian northeastern regions, skylines (pole type) are preferred because they are light and have a medium size, even if the cable car skyline type is still in use in high forests with a slope over 60 percent, where the construction of roads proves difficult. The length of the lines can reach 1 000 to 1 500 m.
Compared to other harvesting methods, the two above-mentioned skyline systems considerably reduce damage to forests and timber, as well as road density. But it would be unreasonable to think that such installations do not require a minimum road network.
Trentino is one of the few Italian regions which focus attention on the forest road network Actually, more than 60 percent of wood-producing forests are well served by a road network and, of these, 65 percent are high forests.
This is why access to a forest with a wood cover strip on a slope 100 m wide on the left and on the right of the forest road is adequate. Geometrically speaking, the distance decreases as the slope increases, e.g. for example, for areas with a slope ranging from 40 to 70 percent (which represents the larger number in this area) the well-served forest belt is situated between 270 m and 175 m from the road, measured along the maximum inclination line of the slope. By doubling these figures we obtain the maximum space between two adjacent roads.
In areas where roads and tracks are at a distance of 250-300 m, on slopes below 40 percent, the use of winch-equipped tractors allows man/day yields ranging between 1.5 and 5 m3, for small-size products, and from 6 to 18 m3 for large-size logs.
In the case of forests located on slopes over 40 percent and roads at distances of 400-750-1 200 m, pole type skylines are used in the first and second cases, and traditional cable car skylines in the last case. Daily man yields amounted to 8-10 m3 in the first cases and to 5-8 m3 in the case of cable car skylines.
During the last few years, sectorial research carried out by the C.N.R. with its two Institutes, has focused attention, in particular, on the clearcutting of coniferous plantations, using light mechanized equipment which requires minor investments with due regard to the environment and society.
The first concern was to try to reuse old tracks, 100 to 150 cm wide, with no intervention or, where necessary, with minor modifications. Then the aim was to integrate man's work and that of drought animals, which have nearly disappeared from the mountains, with appropriate equipment.
In forests located on terrains with gradients below 30 percent, tracks with a slope below 10 percent have been rearranged and access tracks have been opened in between tree rows.
With this type of network, wood harvesting has been carried out by means of an ATV Vimek Minimaster 101, to which a fibreglass shield or a small trailer has been attached. With such equipment, it was possible to pass through tree rows up to transversal slopes with a gradient of 25 percent. Yields recorded on sites mainly composed of pines and Douglas, at a distance of 100-150 m from each other, vary between 1.5 and 3 m3/hr/man.
In areas with transversal slopes of the order of 30 to 40 percent, a semi-tracked auto-levelling tractor, built by the Institute for Research on Wood, has been used. The machine, still at a prototype stage, is 130 cm wide; at the front it is equipped with a two-cylinder winch, a 37 kW engine and a swivel seat. This conception and its auto-levelling ability allow it to get close to the loads without having to manoeuvre on rough terrain situated on disrupted tracks.
Indicative yields concerning the concentration and logging, on distances ranging from 60 to 150 m, range from 2.5 to 4 m3/hr/man.
A third type of machine has been used, the Vimek 430 processor attached to an agricultural tractor.
This equipment has been used in areas having 2-3 m wide tracks, at a distance of 100-200 m from each other.
Trees with branches have been gathered by an ordinary radio-controlled winch. Then trees have been delimbed and cut in 2 m long pieces. This process has been adopted in all test areas.
Measured yields vary from 2 to 3 m3/hr/man.
Conclusion
Wherever it is possible to use a tractor for logging, silviculture is not subject to any restriction as it can be practised even when low timber exploitation is carried out (20-30 m3/ha), but this implies the existence of a high road and track network density.
The exploitation with both types of skylines does not necessitate a road network as dense as the one required above but it restricts silvicultural activities, as it can only be carried out, from an economic viewpoint, in the case of a minimum threshold of timber exploitation (40-80 m3/ha).
It can be noted that exploitation costs, when a tractor is used, are one-third those reported when skylines are used in the same conditions.
Actually, in Italy, study groups look into the possibility of re-arranging old tracts and of using light mechanized equipment in order to implement silvicultural activities in areas reforested with pine species, which have practically never been subject to silviculture.
The first results are rewarding from an environmental as well as an economic point of view: utilization costs, for trees of 0.050 to 0.150 m3 each, remain steady between Lit 50 000 and 60 000 per m3, which means acceptable values for the type of exploited products.
