engleski

Ecoefficient Timber Forwarding on Gley Soils

This research presents possibilities of timber forwarding in an efficient and environmentally friendly way, under conditions of limited bearing capacity of gley soils of Croatian lowland forests due to their increased moisture all the year round. Reduced soil bearing capacity causes restricted mobility and decreases the forwarder productivity, and also increases the level of damage caused to forest soil, reflected in its compaction and rutting. The analysis was carried out on the example of a medium-weight six-wheel forwarder Valmet 840.2 (12 t payload) and this analysis involved as follows: 1) the effect of load reduction on forwarder efficiency, 2) forwarder environmental soundness under conditions of limited soil strength based on nominal ground pressure (Mellgren 1980) of front and rear wheels of the vehicle depending on the mass of loaded timber, vehicle with narrower (600 mm) and wider (710 mm) tires, or with tracks on wheels of the rear (bogie) axle. The limit value of environmental soundness would be the allowed ground pressure of limited bearing capacity <60 kPa (Owende et al. 2002). The results of efficiency analysis of timber forwarding showed that the reduction of load under conditions of limited bearing capacity of gley soils, as a measure for providing vehicle mobility as well as for diminishing the level of damage caused to forest soil, is highly unacceptable due to the decrease of productivity and increase of unit costs. The analysis of nominal ground pressure under wheels of the front axle and wheels (tracks) of the rear axle, showed that under conditions of limited soil bearing capacity: 1) the forwarder nominal payload may be used and that efficient timber forwarding may be performed, 2) the environmental soundness can be provided by the application of four-axle (eight-wheel) forwarders equipped with wider tires and half-tracks on wheels of front and rear bogie axle of the vehicle. These results should be used as guidelines for purchasing forwarders, and such approach would provide in future ecoefficient timber forwarding under conditions of limited bearing capacity of gley soils in main felling sites of lowland forests and elsewhere.

lowland forests; forwarder; nominal ground pressure; efficiency; environmental soundness

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