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Silver birch (Betula pendula Roth) is a popular tree species forming stands throughout most of Europe, and in Poland birch is one of the most common broadleaved species. It grows in rather poor soils, very often as a mixed species with Scots pine (Pinus sylvestris L.). In Central Europe, the trunks of birch trees often have sweeps, and older trees have thick branches. Consequently, harvester thinning operations in birch stands can be challenging, especially when trying to process logs from the top parts of trees, and this eventually has an impact on productivity. The objective of this research was to determine the harvester productivity curve for birch with particular attention to the production of logs from the top part of the tree as industrial timber. The research was carried out in stands in North and North-West Poland. Altogether 21 tests were completed in 16 stands in which nine harvesters were used (eight different models). The mean diameter of the harvested trees was 23.7 cm with a mean height of 21.7 m. The productivity obtained without delays was on average 21.98 m h -1 and varied from as low as 5.14 to a maximum of 44.66 m h and depended mainly on harvested tree size. It was also confirmed that the top diameter of the last log depended on the DBH and not used tree biomass for logs amounted to 10%. Based on this relationship, the model created may be used to predict the volume of biomass (harvesting residues) that can be obtained from birch stands when harvesters are used for thinning when processing industrial timber. -1 |
