A comparison of harvesting productivity and costs in thinning operations with and without midfield

Abstract

Mechanised thinning operations can be carried out in the forest where skid roads are provided on which harvesters and forwarders can move. In the transition to continuous cover forestry (CCF) it is better to keep a thinner network of skid roads in the forest. Instead of tracks for harvesters and forwarders, these areas can be used for younger generations of trees. Moreover, fewer skid roads in the forest environment make the stand more natural. Fewer skid roads were introduced in this research as an alternative thinning operation with midfield 1 1 The thinning operation with midfield (MF) is also carried out using skid roads. The name “with midfield” (MF) is short for “with midfield and skid roads”. The midfield is the area between skid roads in which the trees are beyond the reach of the harvester boom; trees in this midfield area are cut with a chainsaw and felled in the direction of the skid roads (with the treetops in reach of the harvester boom). (MF) to the most popular mechanised thinning operation with skid roads 2 2 The thinning operation with skid roads (SR) uses approximately twice the number of skid roads as the “with midfield” (MF) operation. (SR). The aim of this paper is to analyse the productivity and economic aspects of thinning operations based on harvesters and forwarders, where there are different distances between skid roads. In both of the operations, harvesters and forwarders were used, but in the MF operation a chainsaw was additionally used to cut trees beyond the reach of the harvester boom. The distances between skid roads in the MF operation were 35–38 m, while in the other they were 18–20 m. The research was carried out in premature pine stands in a flat terrain in Poland. Bigger productivity and lower costs were found in the MF thinning operations. In the younger 44-year-old stand, the average harvester (Timberjack 770) productivity (in operational time) in the MF operation was 5.87 m 3h −1 and in the SR operation 4.52 m 3h −1; forwarding provided by the Vimek 606 6WD achieved a productivity of 5.03 and 4.52 m 3h −1, respectively. In the older 72-year-old stand, the Timberjack 1270B productivity was 11.53 m 3h −1 in MF and 8.70 m 3h −1 in SR; the Timberjack 1010B forwarder achieved 11.22 m 3h −1 (MF) and 8.84 m 3h −1(SR). The costs of harvesting and forwarding 1 m 3 of wood were lower in the MF operations. In the younger stand, harvesting costs were 5.78 €/m 3 (MF) and 6.72 €/m 3 (SR) while forwarding costs were 1.94 and 2.18 €/m 3 respectively. In the older stand, harvesting costs were 5.58 €/m 3 (MF) and 6.78 €/m 3 (SR); the forwarding costs were 2.65 €/m 3 (MF) and 3.41 €/m 3 (SR).