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Mountain spruce forests in Central Europe decline under storms and bark beetle calamities driven by climate change. A stabilisation by planting rare or missing tree species is expensive and requires funding. A funding policy should mitigate climate change and support biodiversity. The goal of this study was to identify a conversion strategy of even-aged spruce-dominated forest stands to uneven-aged mixed stands with spruce (Picea abies (L.) H.Karst.), beech (Fagus sylvatica L.), and fir (Abies alba Mill.). A simultaneous nonlinear optimisation of the number of planted trees and harvested trees per species and per period schedules stand treatments aiming to maximise the long-term financial outcome. Planting modelling extends a density-dependent stand-level matrix transition model based on diameter classes with an age-class-based model for artificial regeneration. An optimal conversion strategy was applied for five funding policy schemes, each for five initial states representing different stages of age and species composition typical for spruce forest conversion in the mountain zone of the Western Carpathians. Only 50% and higher funding of planting costs for the minor/missing fir and beech species facilitates a substantial increase of their shares in stand volume. Funding decreases the volume failure due to mortality. Funding increases the standing and harvested volume, which mitigates climate change by increasing the carbon sequestration. Funding causes unintended effects on ecosystem services by lowering harvest diameters, decreasing the volume of less profitable beech, and temporarily reducing the stand density aimed at supporting plantings and their diameter increments. [ABSTRACT FROM AUTHOR]

This study presents economically optimal management of uneven-aged mixed mountain forests that takes into account tree growth variability. We divided 9846 silver fir ( Abies alba), beech ( Fagus sylvatica), and spruce ( Picea abies) trees measured on 898 forest inventory plots in the Snežnik and Leskova dolina management units (4905 ha, Dinaric mountains, Slovenia) into three growth classes (slow-, medium-, and fast-growing trees) to simulate optimal forest management over a period of 100 years with respect to changing tree growth, stand density, diameter distribution, and tree species composition. We developed a density-dependent and stage and growth-structured matrix transition model which-simultaneous to the long-term stand dynamics projection-scheduled optimal harvesting to maximize the net present value using a nonlinear approach. The ecology of tree species was considered by using tree species-specific and stand-density and diameter-dependent logistic functions for ingrowth, transition, and mortality. The model projected a shift in tree species composition from fir-dominated to beech-dominated forests within 100 years. A change from harvesting slow- and fast-growing trees as if they all had medium growth to growth-sensitive harvesting increased the net revenue and maintained the uneven-aged stand structure. Optimal harvest diameters varied among growth classes, time periods, and tree species according to the economic maturity of individual trees and ranged from 12 (pre-commercial thinning) to 72 cm (target diameter). The simulation highlights the potential of improved bio-economic models for increasing yield from uneven-aged forests and scheduling optimal management regimes with multiple objectives. [ABSTRACT FROM AUTHOR]

Abstract: A new modeling approach which combined survival probabilities for spruce with financial optimization showed a considerably reduction in financial risk in spruce (Picea abies [L.] Karst.) stands with an admixture of a 20% proportion of beech (Fagus sylvatica L.). The admixture enhanced the stability of the spruce component against natural hazards, such as storm or insect damage. Here, these new survival investigations were integrated into a bio-economic modeling approach called silvicultural economics. A new failure model which includes the benefits of ecological interactions for decreasing hazard risk for spruce was developed. The modeling technique is based on Monte-Carlo-Simulation and on simultaneous portfolio optimization of management strategies under risk. Area proportions were allocated as decision variables to each tree species and to regeneration harvests at various points in time in order to achieve the maximum financial return given a predefined, acceptable risk. The simultaneous optimization led to a mixed – and, through long regeneration periods – to an uneven-aged forest stand, for almost all predefined risk-levels. In addition, for a selection of possible even-aged tree species compositions, a stand-level mixture (including the species interactions of the new model) was compared with the same species proportion at the stand level, but consisting of two separated parts of spruce and beech (thus excluding species interactions). For all even-aged and interacting mixtures that were investigated, a higher expected return and a lower financial risk were achieved when compared to the identical even-aged mixture proportions without interactions. When the timing and distribution of regeneration harvests was also optimized (as opposed to using a clear-cut strategy) there was a slight loss in financial return, but the reduction in risk was even greater, given the same tree species proportion – especially in cases with a low beech admixture. Compared to the simulation which excluded the stabilizing effect of beech on spruce, the variant with interacting tree species allowed for higher spruce proportions and shorter regeneration cycles for the same acceptable risk. [Copyright &y& Elsevier]

Steadily increasing damage to Norway spruce forests in Europe has caused researchers and managers to consider whether these forests can be converted to more stable ecosystems. In a central European mountain region, we investigated whether management systems (MSs) specified by regional stakeholders provide sound alternatives to the currently applied management. We used the forest model Sibyla to explore whether the tested MSs differ in their sensitivity to climate change in terms of altered biomass production, stand structure, forest damage, and financial outcome. The tested MSs were no-management (NM), currently applied management (BAU), and management based on the preferences of forest managers (FM) or on the preferences of other stakeholders (OSH). With NM, spruce remained dominant during the simulation period 2010-2100, and the rate of damage significantly increased. Spruce also remained dominant with FM, while the abundance of non-spruce species significantly increased with BAU and OSH. The rate of salvage logging converged at 50% of the total harvest for all MSs up to 2050. Climate change reduced biomass production (−15%) with all MSs but had a negligible effect on biodiversity indicators. The average initial value of the simulated stands was 20,000 € ha and the nominal value in 2100 was between 1900 and 10,900 € ha. The Net Present Value calculated with the 2% interest rate was negative during the whole simulation period (−5600 to −18,500 € ha in 2100). Effect of climate change on all financial indicators was negative. Our findings indicate that secondary spruce forests are highly vulnerable and that the systems proposed by both forest managers and other regional stakeholders failed to significantly reduce forest damage and stabilize forest production. [ABSTRACT FROM AUTHOR]