Current issue: 55(3)
Under compilation: 55(4)
The effect of harvester operator tree selection or prior tree marking in thinning operations on satisfactory results and performance has been widely discussed. In harvester operator tree selection, the machine operator decides on the fly which trees are selected to remain or cut. The objective of the study was to analyze the effect of prior tree marking, thinning method and topping diameter on harvester performance in low-diameter thinning operations. The entire thinning operation was captured using video technology. Overall, 2.36 ha divided into 48 plots with 5202 trees were thinned with an average diameter at breast height (dbh) over bark for all plots of between 12.5 and 14.7 cm. In total, 3122 trees were harvested, resulting in 60% removal of stem number over all plots. The harvester achieved a mean productivity of 7.38 m3 PMH0–1 with 1.48 m3 PMH0–1 SEM, with stem volume having the major influence on harvesting productivity. Prior tree marking, topping and thinning method did not significantly affect productivity. Without prior tree marking by the foresters, harvesting removal was shifted toward lower diameters. Within the unmarked plots, 7.0% of the residual trees were damaged compared with 3.2% in marked plots.
In South-West Finland the usual method to make leaf fodder for cattle has been to cut the branches and collect the new sprouts again next year. According to this review, the most common tree species to be topped is Betula sp. Downy Birch (Betula pubescens Ehrh.) grows shoots easier than silver birch (B. pendula Roth). The topped forests are usually small and situated near the settlements, next to the fields and meadows. The birch trees are typically cut when they are 15-20 years old. Regularly topped birch rots easily and seldom exceeds 50 years. The capacity to grow shoots depends on the age of the tree, site and time of the cutting. The risk for rotting can be decreased by removing only part of the shoots and cutting the shoots a short distance from the base of the shoot. Collecting leaf fodder decreased in Finland, and was common only in the South-West Finland and Åland.
The PDF includes a summary in German.