Aksel Granhus
Avdelingsleder/forskningssjef
Sammendrag
Det er ikke registrert sammendrag
Sammendrag
Forest age structure is one of the most important ecological indicators of forest sustainability in terms of biodiversity, forest history, harvesting potentials, carbon storage, and recreational values. The available information on the forest age is most often stand age from forest management plans or national forest inventories. Depending on the definition, stand age is often not a good indicator for the biological age of the dominant trees in a stand. Here, we used 6,998 increment cores from dominant Norway spruce (Picea abies L.) and Scots pine (Pinus sylvestris L.) sampled on National Forest Inventory (NFI) plots throughout Norway to gain a better understanding of the age structure of Norway spruce and Scots pine stands in Norway, and on the relationship between the recorded stand age and the biological age of dominant trees on the NFI plots. In forest with stand ages indicating that the stand was established after the abandonment of selective harvesting in favor of even-aged management dominated by clear-cutting methods (ca.1940 C.E.), we found no systematic difference between the biological age of the sampled trees and the stand age assessed by the NFI. In older stands, there was a large difference between the stand age and the age of the overstory trees with the sampled age trees occasionally being hundreds of years older than the stand age. Our study also reveals that the area of forest with old Norway spruce and Scots pine trees ≥ 160 years old is considerably higher than the corresponding area estimate based on information derived from the stand age only. These results are important as the stand age is often used to characterize status with respect to forest naturalness, biodiversity, guide protection efforts, and describe the appropriate and allowed management activities.
Sammendrag
This study examined the economic potential of thinning in pure, even-aged Norway spruce and Scots pine forests in Norway based on simulated stand dynamics using plot data from the Norwegian national forest inventory. Simulated management scenarios included fully mechanized thinning from below of varying intensity including no thinning. The economic evaluation was based on comparing the equivalent annual annuity of the unthinned scenario and the economically best-performing thinning scenario for each studied plot. The findings suggest that only late thinnings in well-stocked stands with sufficiently large trees are economically beneficial. Furthermore, to be economically superior, a thinning intervention itself had to generate enough profit, meaning that the revenue from thinning needed to sufficiently exceed the costs. Profitability of thinning scenarios varied with discount rates and timber prices and depended on whether rotation age was based on maximum net present value or maximum mean annual increment. Thinning was less often profitable in pine compared to spruce stands. This study is among the few that model stand development considering post-thinning stand structures with systematic machine trails while assessing the profitability of such thinning operations.
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