Harvester Efficiency During Thinning Operations in Alder Planted Stands with Some of Coppice Origin

In Central European conditions, harvester use becomes more popular for broadleaved tree species, though there are still some difficulties with effective delimbing of satisfactory quality. Considering these issues, economic aspects are ultimately crucial when deciding on the use of harvesters and assessing the effectiveness of their productivity. The objective of the present research was to apply different harvesters in thinning of alder stands to determine their productivity level focusing on the use of tree trunk for logs. The study was carried out in alder stands under thinning where five different harvesters were used in nine stands, five of which were of coppice origin. Additionally, in six cases, harvesting was done after the growing season and in three cases during the growing season, when trees were covered with leaves. An average productivity was 14.42 m3 PMH0-1, with maximum values of 24.34 m3 PMH0-1 in a coppice stand, and 23.66 m3 PMH0-1 in a planted stand. Delimbing was carried out in the tree crowns with the mean diameter as small as 7.9 cm under bark, which shows very good use of the tree trunk for logs. It was also established that the thicker the tree, the bigger the top diameter of the last log, leading to bigger biomass production, e.g. for energy purposes, but also with smaller effectiveness of log processing.