Zrywka drewna średniowymiarowego w drzewostanach trzebieżowych przy użyciu ciągnika rolniczego z przyczepą nasiębierną

The amount of timber extracted from Polish forests is expected to increase in near future. The most common equipment for timber extraction is an agricultural tractor with a trailer equipped with a hydraulic crane. The research was carried out in the Wymiarki Forest District (Regional Directorate of the State Forests in Zielona Góra) in the third (TP1) and fourth age class (TP2) in Scots pine stands, during extraction of timber from thinning. Extraction was carried out using BELARUS MTZ 1221.2 agricultural tractor with PALMS 120 forest trailer equipped with PALMS 700 hydraulic crane. The scope of the study was to conduct time studies of extraction process and to estimate the extraction productivity as well as time and fuel consumption. Working time was measured by stopwatch, while the forwarding distance was determined with measuring wheel. The exact number of logs in each load was established. Average volume of each log and each load was calculated. The dominant work time category was effective working time 74.78% (TP1) and 73.60% (TP2), while the prevailing work task was loading 56.82% (TP1) and 58.99% (TP2). In older stands, the extraction productivity was higher than in younger ones reaching 11.28 and 9.62 m³/h, respectively. Statistical analysis proved that extraction distance significantly affect productivity and time consumption. With increasing extraction distance productivity decreases and time consumption increases. Fuel consumption was exactly the same in younger and older stands (0.52 l/m³).