Kasvavate puude vigastamine harvendusraietel

Thinning should promote the optimal growth and good health of a forest ecosystem. However, several residual trees usually suffer mechanical damage in stands after thinning operations. This research was conducted to determine the extent, cause and location of damage to residual trees during felling operations and timber extractions in the cut-to-length system in hemiboreal forests in Järvselja, Estonia. Field measurements were carried out in 30 thinning sites in 2017 and 2019. There were 57.6 damaged trees per hectare (7.8% of residual trees) on average. The number of damaged trees per hectare was not dependent on the method (harvester or manual felling) and season (winter period or summer period) of felling, however it was dependent on stand density. There were 23% root damage, 9% root collar damage and 68% stem damage out of all damaged trees. The common causes of residual tree damage were driving damage, falling tree damage and harvester saw damage. The strip roads covered 19% of the thinning area; the mean width of strip roads was 3.76 m. Thinning is certainly an important silvicultural measure whereas careful planning and execution should keep direct and consequential damage to the stand as minimal as possible.