Browsing by Subject "above thinning"

The effects of below and above thinning of the growth and yield of pine and spruce stands was last researched at the beginning of the 1990s. In the previous studies, the research periods have been at most 25 years. The main objective of this research was to investigate how above and below thinning affect the growth and yield of pine and spruce stands in a long-term period. The second objective was to determine the growth reaction of different tree crown layers. Research material consisted of seven pine stands and tree spruce stands which were located in Southern Finland. The average study period of research plots was 37 years. The research demonstrated that above thinning applies well to the thinning for old pine stands when thinning intensity is about 20%. Above-thinning improved the average basal area growth of pine stands by 12%, dominant height growth by 4.7%, diameter growth by 5% and volume growth by 7.9. Above thinning also improved roundwood yield by 3.9% on average in 42 years, compared to below thinning. On average, 3.8% more roundwood accumulated from above thinnings and final cuttings than from below thinnings. The growing stock in the final measurements represented accumulation in the final cuttings. Log accumulation was three times larger in above thinnings than below thinnings, but in final cuttings log accumulation was 18% bigger in below-thinned pine stands. Above thinning positively affected the growth of crown layers 1, 2 and 4. In below-thinned pine stands, growth was biggest on average in crown layer 3. Based on the average results of three spruce stands, the above thinning improved basal area growth on average by 9.3%, dominant height growth by 1.2%, and diameter growth by 11.8%, but in the below-thinned pine stands volume growth was 2.4% greater. Roundwood yield per year was on average 1.6% bigger in above-thinned spruce stands. In total, 6.7% more roundwood accumulated from final cuttings and below thinnings. More logwood accumulated from the above thinnings, but in the final fellings the situation for the thinning methods was the opposite. There was not an obvious line between the growth and yield of the different crown layers and the main reason was the variation between experiments. On average, the first and second crown layers mostly benefited in above-thinned spruce stands when the research period was short, but for a research period of over 50 years, the situation for the thinning methods was the opposite. The results from the spruce stands are not as reliable or generalized as those from pine stands, because in spruce stands, the extent of the research data was slightly limited and it also varied considerably. The growth and yield results provide a reliable picture that above harvesting is a suitable thinning method in pine stands if the thinning intensity is low. There is a need for further research on spruce stands so that it will be possible to draw more reliable conclusions.