Browsing by Subject "silver birch"
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(2017)This study aimed at conducting a baseline for optimal harvesting schedules with economic criteria for Scots pine, Norway spruce and silver birch in Estonia. Additionally, this study aimed at providing comparison to previous findings about optimal schedules in boreal forests and recommendation for practitioners. Faustmann’s (1849) forest rotation theory provides the theoretical foundation for the thesis. The study was performed by including Estonian whole-stand forest growth models and local timber prices and forest regeneration costs in the optimization, which was based on the Hooke and Jeeves’ (1961) direct optimization method. Scots pine was found to be the optimal species in most site classes, silver birch being the optimum in the most fertile site. The schedules for silver birch were found to be less sensitive to changes in the rate of interest, site fertility and timber price than the conifers. The current legal restrictions lead to longer rotations, more thinnings and economic losses when compared to the unrestricted optimal scenarios. The optimal number of thinnings in most scenarios for all species turned out to be three, if the legal restrictions are followed. In general, the optimal rotation periods were found to be shorter and the timing of the first thinning earlier in many scenarios than in Finland. Also the optimal number of thinnings was found to be more stable in Estonia than in Finland. It was found that if the initial stand stocking for the main tree species falls below a certain threshold in mid-rotation mixed-species stands including less valuable broadleaves, it is optimal to clear fell the stand immediately and regenerate the stand according to the optimal stocking recommendations. From the practical point of view, given the current limitations regarding the timing of clear fell, forestry practitioners have the most value creation potential in improving the forest regeneration methods and thinning schedule. In comparison to Finnish studies, it was found that there exists many similarities regarding the schedules and the suitability of species for different forest sites between the findings of this study and previous Finnish studies and the Finnish silvicultural recommendations. Thus, the extensive Finnish recommendations and findings provide a good basis for practitioners also in Estonia. However, given also the found differences, harvesting schedules in Estonia should be developed in more detail for more sophisticated recommendations for local practices.
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(2022)Boreal forests fulfil a myriad of ecological, social and economic functions in modern society, which is why it is crucial to manage them in the best way possible. The prevailing forest management strategy in Finland has been rotation forestry, but a Finnish citizens’ initiative and the new EU forest strategy for 2030 have for ecological reasons been calling for a reduction in clearcuts and a switch to continuous cover forestry. While a growing number of economic-ecological optimization studies illustrate the economic aspects of optimal management regime choice in Nordic conditions, the understanding remains incomplete. To contribute to this line of research, this thesis studies the economically optimal management regime and species composition of mixed-species boreal forests with a previously unexamined species combination: Scots pine (Pinus sylvestris L.) and silver birch (Betula pendula Roth). The analysis is based on a theoretically sound and generalized stand-level economic-ecological model that maximizes the net present value of forestry income. In this setup, the optimal management regime is determined endogenously and flexibly, by dynamically optimizing both the rotation period and the timing and intensity of thinnings in a tri-level structure. All model details are empirically estimated. Forest stand development is described by size-structured empirical growth models by Pukkala et al. (2011, 2013) and by Pukkala et al. (2021), of which the latter has not been used in this line of analysis before. The results of this thesis show, for the first time empirically, that it can be economically optimal to conduct near-clearcuts without investing in artificial regeneration afterwards. Near-clearcuts create favourable conditions for utilizing the unharvested young trees and natural regeneration of pioneer species in generating a new tree cohort. This management strategy is found to be suitable for birch-dominated pine–birch stands with a 1% interest rate, as well as pure birch stands. With a 3% interest rate, continuous cover forestry becomes optimal for mixed stands. A further outcome of this thesis is that continuous cover management of pure pine stands is found to be more viable than in previous optimization studies. Further, it is shown that it is economically beneficial to let birch regenerate in a pine stand and even dominate it, due to improvements in overall ingrowth. The characteristics of the optimal solutions are, however, dependent on the ecological growth model used. In light of the cases studied in this thesis, neither rotation forestry nor continuous cover forestry is categorically superior in terms of timber income. There are demonstrably many cases where taking advantage of the environmental benefits of continuous cover forestry and higher tree species diversity is optimal also with respect solely to maximizing timber revenues.
Now showing items 1-2 of 2