Felling was done by fellers working on a private contract basis, which means they get paid an agreed fee per m3 of timber produced; the paid amount is in accordance with the contract negotiated between the enterprise and the fellers. This might result in lower costs for the forest enterprise but requires a high degree of supervision by the forest staff.
Working on a private contract basis induces fellers to produce the largest number of units in the shortest possible time and with a minimum of delays. One cause of delays might be the observance of felling instructions; therefore supervision has to concentrate on direction felling in order to avoid damaging the natural regeneration and to facilitate extraction of felled trees lying in the logging direction.
9.2.1. Setting up the crane
In order to decrease the time needed to set up the construction crane the assistant who is responsible for unhooking the load might assist the crane driver in preparing the vehicle for supported operation; for example, adjusting the square-sawn timber between outriggers and ground or joining the hoisting equipment to the hook-block so that the crane operator can concentrate on the crane operation.
At the same time, the second assistant who will be hooking the load should go to the felling area so as to plan the work in the best possible way, especially if the height of the natural regeneration necessitates the operation to be directed by radio communication.
The locations for setting up the crane are more or less predetermined by its effective radius of action and the space left should be used to provide the crane operator with the best possible view. As mentioned above, its influence on the logging performance cannot be verified by statistical analyses but being able to view the felling site was valued highest by the crane operator when asked to rate the major influences on the logging performance.
9.2.2. Logging operation
According to the operator's opinion, logging done by the crane is quite different from the usual crane operations at building sites where construction cranes are usually used.
The mental strain is much greater during logging operations because of the high number of crane and boom movements per unit of time. For example, a swinging boom caused by lifting a tangled tree makes the driver apprehensive of overturning the vehicle and increases his mental strain as well. Apart from other factors the driver's previous experience with logging operations has an influence on the logging performance because crane operators often have difficulties when they are logging trees for the first time.
9.2.3. Hooking - unhooking
The assistant hooking the load has to direct the operator by radio so that the boom is aligned to the felled trees that are to be logged in order to avoid lateral pulling of the load which would otherwise delay alignment and consequently decrease the performance. Furthermore, the assistant has to arrange the order of trees or assortments for logging so that rehooking can be avoided, particular-ly when trees are tangled. Using a synthetic sling instead of an iron chain facilitates the work done by only one worker, therefore reducing labour costs.
The second assistant unhooking the load has longer waiting periods compared to the assistant at the felling area so the two assistants should alternate with each other in order to avoid fatigue.
Helmet and protective gloves are absolutely necessary for both assistants because they handle the metal log tongs and are also exposed to the risk of falling limbs from the lifted load.
9.2.4. Load size
Differences in logging performance based on the number of assortments per load could not be examined because after some crane movements with two logs per load the operator decided to transport only one log or tree (see Photo 9).
This decision was reached for various reasons: It was impossible to align the boom to more than one tree and at the same time avoid lateral pulling. Also, during touch down of the load with logs of different lengths, the crane driver was unable to place the logs in the desired direction because the longer log touched down first, causing the load to swing; this swinging motion exposed to danger the second assistant at the landing site.
Photo 9. Transport of only one log or tree enables the crane driver to position the load exactly in the desired direction.
9.2.5. Method of transport
Transporting the trees or long logs horizontally - with log tongs fixed on both ends - could be useful in preserving the natural regeneration from damage but it requires that trees lie in the optimal radius; otherwise the log has to be transported in a vertical position, first with "raised head" and rehooked afterwards. Rehooking has to be avoided whenever possible in order to prevent increase in cycle time and consequently additional logging costs.
9.2.6. Length of assortments
The statistical analysis did not demonstrate that the length of assortments had any significant influence on the cycle time. However, it should be kept in mind that in relation to the height of the natural regeneration the technically possible maximum transportable length should not be completely made use of so as to assure the best possible preservation of the remaining young trees.
9.2.7. Logging distances
The statistical analysis showed that the cycle time was more than doubled when logging distances over 35 m were involved. This distance, measured from the vehicle to the load, corresponds with boom length plus the hoisting equipment length. Above this distance the assistant at the felling site had to pull out the hoisting equipment thereby causing a substantial increase in cycle time.
9.2.8. Load volume
Statistical analysis of the cycle time showed that both groups with a load volume of more than 1.5 m3 differ significantly from group 1 with the highest number of loads. The cycle time for group 2 (1.5 - 2.5 m3) is almost twice the amount and group 3 (more than 2.5 m3) is more than twice when compared to the cycle time for group 1.
In relation to the logging performance the higher volume per load compensates the higher cycle time according to the equation for calculating productivity so that the analysis of variance with the same group classification, as mentioned above, showed no significant difference between the groups for the variable productivity.
As a result of setting up the wood processor on a forest road the operator has to careful-ly place produced assortments and debris so as to leave a clear work space. When logged trees are piled too high due to a small landing space, instead of a low pile on an adequate landing, the result is that the tops and branches become more tangled and extra time is there-fore needed to select the least tangled trees. This requires a skilled operator familiar with these working conditions, which should be taken into account when the machine is hired.
Since the felling operation is very different from the operations of both the construction crane and the wood processor, the work phases cannot be done simultaneously. If the felling operation were done simultaneously with the construction crane and wood processor, the felling not only would be hazardous to the workers but would require four fellers to obtain the required number of trees and logs to permit the simultaneous operations of the construction crane and wood processor at full capacity. Apart from the different time elements involved, the logging might be interrupted by felling trees and vice versa, resulting in extra costs due to delays.
Directional felling and the best possible preservation of the natural regeneration cannot be expected if the fellers are pressed for time; the advantage of this way of logging therefore is defeated.
The productivity rate of the logging phase on study area B shows that it is appropriate to use the construction crane in combination with the processor. Because of the high costs for hired machines their combined operation has to be planned very well.
Therefore it might be useful to start with the logging operation one day earlier in order to have a buffer of trees ready for processing should there be delays in the logging operation due to minor machine repairs or in case the STEYR KP 40 is capable of processing more trees than the FAUN RTF 40-3 is capable of logging. Only when the supply of trees is assured can the combined operations of logging and processing be performed at reasonable costs.
The continuous operation of the wood processor without interference from finished assortments or debris should be made possible by hauling, which begins after completion of processing so that the wood processor can remain fixed at one site during the entire operation; hence time consuming changes of location can be minimized.
9.5. Environmental impacts
Today's goal in forest regeneration is to obtain recruitments coming from autochthonous stands. These recruitments should provide stable stands that are best suited for both natural and today's man-made impacts to the forest ecosystem and should be able to ensure all functions requested by the community. New silvicultural and harvesting techniques have to be found so that the timber yield expected by the owner of a forest estate - along with the protection function, welfare function and recreation function requested by various groups in the community - can all be fulfilled at the same time. Clear felling systems that may cause erosion and landslides due to inadequate soil protection during their regeneration phase will be replaced more and more by small-scale treatment and selection of individual or groups of trees to be harvested.
However, group felling and other small-scale harvesting cuts require a high forest road density due to their proportionally small harvesting volume per area so that otherwise useful logging and processing equipment become unprofitable; this is because installation time is excessive in proportion to time of operation. The construction crane with comparatively short time needed for setting up can be an alternative method in certain situations so as to ensure the advantages of cable logging - in particular the "lifted load" avoids excessive damage to young trees of the natural regeneration; furthermore it avoids soil compaction and wounding of the ground, which may frequently be the initial stage of soil erosion. These advantages are not lost during the processing phase because the wood processor is also set up on the forest road. Logging by construction crane might be an alternative, as well, if the terrain is inaccessible because of wet soil, slope gradient or obstacles, such as boulders, covering the ground.
Small gaps occurring in the natural regeneration - either spontaneous or the result of damages from incorrect or faulty directional felling or logging operations - should be restocked with desired tree species.