%0 Research articles %T Time consumption and harvesting cost in continuous cover management of peatland forests — A case study %A Niemistö, Pentti %A Jylhä, Paula %D 2023 %J Suo - Mires and peat %V 74 %N 1-2 %U http://suo.fi/article/10825 %X

The present case study constructed tree-level time-consumption models for thinning from above, selection cutting, and gap cutting in continuous cover peatland forestry based on time study data. In addition, the harvesting costs from stump to roadside were calculated. The cutting trial was conducted in a drained peatland forest in Western Finland in the winter of 2019. In the trial, an operator with 10-years of experience in mechanized cutting used a mid-sized single-grip harvester. An action camera was mounted inside the harvester’s cabin, and the recorded videos were used to conduct a continuous time study. The removal data were derived from the stm files recorded by the harvester’s onboard computer. The tree-level time consumption of the main work phases was modeled using a mixed linear model, and the auxiliary times and delays shorter than 100 s were allocated to the trees in relation to their predicted total main time consumption. The estimates for the forwarding time were calculated according to the studies by Manner et al. (2013, 2016). The hourly costs of the machinery are based on the studies by Jylhä et al. (2019), Laitila (2008), and Väätäinen et al. (2021).
On average, the tree-level time consumption in selection cutting was 40% higher than in gap cutting. Correspondingly, the time consumption in thinning from above was 47% higher than in gap cutting. These differences were primarily due to the increased time consumption of the harvester in moving between processing points and sorting the timber. In most cases, cutting Scots pine (Pinus sylvestris) was faster than cutting spruce (Picea abies) and birch (Betula sp.). However, the quality defects of pines that had recently reached sawlog dimensions increased the time consumption as the trunks were moved back and forth in the cutting device to determine an appropriate cross-cutting point. Cutting birches with a breast height diameter higher than 30 cm took more time than cutting conifers of an equivalent size because their thick and erect branches hampered delimbing.
The harvesting costs (including cutting and forwarding) were at the same level as conventional harvesting in even-aged forest management. The stand-level cost of harvesting was 9.0 €/m3 for gap cutting, 9.6 €/m3 for selection cutting, and 11.2 €/m3 (VAT 0%) for thinning from above. Due to the large stem volume, the selection-cutting cost was slightly higher than the cost of gap cutting. When thinning from above, a small stem size increases the harvesting cost. The forest haulage cost primarily depends on the load volume and forwarding distance. Increasing the load volume from 8 to 12 m3 for sawlogs reduces the cost of forwarding large-diameter trees. In this case, the harvesting cost in selection cutting was close to that of gap cutting. However, the bearing capability of peatland often limits the load size. Increasing the number of timber assortments tends to increase the harvesting cost. Making small-dimensioned sawlogs instead of pulpwood logs slightly increases the forwarding cost when the breast height diameter of the trees is 15 to 20 cm.