Based on past measurements from 1962 to 2017 on the forest research plots, located in the former slash-and-burn farming areas in the cadastral community of Koprivna, the diameter and height increments as well as volume increments of the two major species – spruce and larch – were calculated. Those set-aside natural research plots have a smaller quadratic mean diameter. The number of trees, however, is higher than in the comparable managed forests. Due to the high-density tree stands in the last thirty years, the spruce and larch trees radial has decreased. In order to determine the impact of environmental factors affecting spruce and larch radial growth, dendrochronological analysis was conducted. According to the dendrochronological analysis of the radial increment of trees the number of years with a negative response has been higher since 1984.