Browsing by Author "Närhi, Lotta"

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.