Mechanised Timber Harvesting on Steep Slopes

In spite of an increase in revenue from timber sales the economic situation of many forestry enterprises is still, in many places, unsatisfactory. The greater supply required for new large saw mills and an increased demand for energy timber means that timber reserves in less accessible areas, which have, up to now, been uneconomical to harvest will have to be mobilized. In the logistic chain from forest to factory harvesting and timber transportation are the most important cost factors. Therefore, it is especially important to activate any latent potential which may lead to an increase in efficiency.

With this in mind training officers from the French speaking cantons had the idea of sensibilizising the forestry service and forestry enterprises by offering further training on the subject of more efficient use of timber harvesting methods on steep ground. Similar events had already been organised in the past few years by the Canton of Bern (Grindelwald 2003), as well as the Association of Swiss Forestry Entrepreneurs (Sarnen 2005).

Four timber harvesting techniques in operation

Four different logging techniques were used to demonstrate to the participants how mechanical harvesting techniques can be optimally put to use on steep ground; how high the costs are and what requirements are needed for planning, organisation and implementation.

In order to be able to choose an optimal method of operation it needs, on the one hand, knowledge of the following: the employed technique, the operational procedure, the employment spectrum, and the advantages and disadvantages of the procedure. On the other hand, cooperation between the protagonists in the timber chain and the ensuing demands on communication, organisation and quality control, are becoming increasingly important. The “use of technology in the forest” aspect was especially highlighted. The four logging procedures showed that varying forestry aims can be achieved even when using modern harvesting techniques.

Potential for cost reduction

A comparison of logging costs between southern Germany and Austria, where similar conditions prevail, and Switzerland show that the hourly charge rates of the various machines are noticeably higher in Switzerland. Due to relatively small ownership structures the machines are often moved from one felling location to another. This results in higher transport costs, but more important is that the yearly workload of the machines is too small.

To combat the disadvantages of small scale forestry ownership, measures need to be taken at the organisatorial level such as: increased cooperation between forest owners and larger quantities of timber produced per felling or per deployment area. The advantages of mechanisation (cost advantages, time advantages, work safety, physical stress of the work force, etc.) can be accompanied by risks if the machines are employed inappropriately (damage to the stand, soil and roots).

The "Best Procedure"

In the past few years the expression “best procedure” has started to appear in conjunction with timber harvesting methods. This expression is often understood as meaning the cheapest harvesting method available to the forest owner. Costs, are in many cases, an important factor, often the most important factor, however they are not the only factor. A “best procedure” can also be understood as being the most optimal procedure, that is to say, a procedure where the aims, under consideration of certain basic conditions, are most optimally fulfilled. These basic conditions include:

    • the topography
    • the soil
    • the access
    • the stand
    • the planned operation
    • the proposed technique
    • the workers
    • the risks for the stand and damage to the soil
    • the weather.

    The right choice of procedure is very important. 60 – 80% of costs are fixed during the choice of procedure and the planning stage. Only 20- 40% of the remaining costs can be influenced whilst the work itself is being carried out. So the choices made at this point are very important.

    Procedure choice process

    Figure 5 shows a concrete example of how the choice procedure could be carried out taking into account the above basic conditions. The first step is the choice of timber harvesting procedure taking into account the topography, the access, soil stability, the timber assortment within the stand and the amount of timber resulting from the cut. In a follow up step the technically possible procedures are then considered from an economic point of view. The timber harvesting costs are then calculated using pre calculations, offers and experience. Profits are estimated using actual market prices.

    In this way the timber harvesting cost free profit is calculated. The resulting cheapest, technically possible procedure will then be considered from the more difficult to evaluate environmental point of view (soil and stand). Depending on the situation a more expensive procedure could be the most optimal. For instance, when the soil stability is critical using a more expensive cable using procedure (mountain harvester) could be a better option than a ground supporting procedure (wheel, track or walking full harvesters) where the risk of damaging the soil is greater.

    Providing an optimal frame work for timber production

    Due to the increased demand for not only round timber, but also for industrial timber and timber for energy the market for timber from forests on steep ground is expanding. Modern techniques are available for efficient harvesting, however their potential has, up to now, not been fully exploited.

    Highly mechanised procedures involve high investment costs, which in turn lead to relatively high system costs (hourly rates for the whole working system). Larger amounts of timber per felling could help reduce timber harvesting costs. Forest owners must therefore cooperate more and make larger amounts of timber available. This could be done through one large felling, or by increasing felling in the same area. What also could be of advantage for the entrepreneurs scheduling is if felling could be carried out during a longer time window.

    By using impressive examples this training event in the Canton of Fribourg showed that in concrete cases timber marking really can be adapted to wood harvesting procedures without endangering Silviculture aims. It is important that the procedure be decided on before the timber marking takes place. One example even demonstrated that mechanical timber harvesting methods can be employed in classical protection forests with their very specific requirements.

    Due to the necessary specific knowledge and experience, the high investment costs and the required annual utilisation highly mechanised timber harvesting systems are mainly being acquired and used by private forestry entrepreneurs. Future cooperation between the various participants in the timber chain, especially between forest owners, that is to say the forestry service and forestry entrepreneurs, is vital. This would mean that the demands for improved planning, organisation, communication and quality control would also increase.

    • Translation: Dawn Meister (Affoltern a. A.)

    Internal links