Productivity of a single-grip harvester in a beech dominated stand: a case-study under Bavarian conditions

Forest conversion from spruce dominated forests to close-to-nature stands with considerable proportion of deciduous tree species is of high importance in Germany. During mechanized harvesting operations, the complex tree architecture and high wood density of deciduous tree species, in particular of beech, pose a challenge during the processing phase. Usually more powerful machinery is required than for softwood stands of comparable age and tree dimensions. This pilot-study assessed the productivity of a TimberPro 620-E single-grip harvester with a LogMax 7000C harvesting head in a mature mixed-wood stand located in southern Germany. A total of 82 trees previously inventoried were harvested using one of two silvicultural treatments (clear-cut or selective-cut). A conventional time and motion study was performed using a hand-held computer on the selected trees that were harvested. Results demonstrated considerable differences in percent distribution of the harvesting related work cycle elements between the two tested silvicultural treatments, particularly with machine movement. Based on single-tree recovered volume estimations, average harvesting productivity during the clear-cut was 31% higher for spruce compared to beech trees. During the selective-cut, average harvesting productivity was 33.9 m³/PMH₀ for spruce compared to 23.4 m³/PMH₀ for beech, thus indicating a 45% higher productivity in spruce recorded during the pilot study.