The effects of the passage of forwarders on soil and damage to spruce root systems along an experi-

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Logging residues offer a significant contribution to the economical profitability and sustainability of forest-based resources. It is always desirable to optimise the harvesting and extraction method to improve the economy of the process along with ensuring sustainability from an environmental point of view. This study compares two harvesting methods, i.e., conventional cut-to-length (CTL) followed by harvesting residue extraction for energy and an integrated harvesting method combining CTL with harvesting residue pre-piling by the harvester followed by the extraction of both timber and logging residues for energy. The study was carried out in spruce stands (Picea abies (L.) Karst.) in South Moravia (Czech Republic) at Pozořice and Kuničky. Two methods utilized by harvesters and forwarders were compared. The first case was a conventional CTL method when trees are felled, delimbed, and cross-cut by the harvester. The resulting logs are pre-piled and then transported by the forwarder. In this case, the harvesting residues remain in the stand. The method does not involve utilizing harvesting residues such as brash mat on striproads but rather extracting them in an independent step as an energy source. In the second case, the resulting harvesting residues are piled up by the harvester to be later extracted by the forwarder. Such extracted harvesting residues are stored at the roadside for seasoning and future comminution. The aim was to obtain input data for internal analysis of a private entity contracting in a logging operation. The client demanded that the increase in time needed for the production of one timber unit with simultaneous harvesting residue preparation be measured. By our estimates, the integrated harvesting method required 33% more (harvester) and 16% less (forwarder) time compared to the alternate method for the extraction of harvesting residues, which in turn results in approximately 8% longer total operational time for the complete operation.

The impact of a small forwarder with the wheeled chassis, tracked-wheel chassis, and tracked chassis traveling on the soil profile was studied. The three chassis types were assessed for the influence of the loading of forwarder cargo space and the degree of tire inflation on induced specific and actual pressures of tires on the soil surface. Penetrometric resistances of soil profile and rut depths in the forwarder driving track were measured. The effect of a layer of logging residues in the forwarder driving track on the size of induced actual pressures was determined. The practice of determining the impact of forest machines on the soil surface by means of a specific tire pressure does not have a full informative value. In the forwarder wheeled chassis, maximum values of actual pressures exceeded specific pressures established numerically by up to 203%. Average values of actual pressures could be reduced by 45% by reducing the pressure of tire inflation, by 70% with the use of tracks, or by 49% by traveling on the layer of logging residues. As compared with the wheeled chassis type, the tracked type of the forwarder chassis induced actual pressures to lower by 81% and the rut depth after ten forwarder passes was smaller by 50%.

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