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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]

• Significant shifts in radial growth of four European tree species during the past hundred years. • Fir showed the greatest recovery, but was found less resistant than beech. • Spruce found to be the least resilient and least resistant in the region. • Long-term BAI growth not affected by species mixture. • A small, but statistically clear effect of species diversity on BAI growth was revealed. Norway spruce (Picea abies), European beech (Fagus sylvatica), silver fir (Abies alba) and Scots pine (Pinus sylvestris) typically co-occur in European forests, but show contrasting response to climate and environmental change. Sustainable forest management therefore depends on species- and regional-specific information. Here, we use tree-ring width measurements of 334 beech, 280 fir, 144 spruce and 63 pine trees from 75 inventory plots in Slovakia to assess the predominant factors that control radial stem growth of Europe's economically most important forest species. All four species exhibit significant shifts in stem growth over the past 100 years. Ring width patterns were, however, not significantly affected by tree species diversity and site elevation. The resistance, resilience and recovery of all species to the extreme summer droughts between 1950 and 2003 suggest that spruce is the species most unsuitable for the predicted warmer and drier future. Silver fir may benefit from warmer conditions, although we cannot conclude that it will not suffer from predicted increased frequency of climate extremes. Forest management in this locality should aim to avoid significant loss of forest cover by replacing Norway spruce monocultures with mixed stands of silver fir and European beech. [ABSTRACT FROM AUTHOR]

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]

Based on a literature review and on a new bioeconomic modelling approach, we investigated whether or not clear-cutting and mono-species forests are the optimal silvicultural strategies under the presence of risk. The model reflects a risk-avoiding attitude and builds upon portfolio theory. The selected tree species and the timing of regeneration harvests constitute a total of 22 management alternatives. Optimal area fractions of the alternatives were combined at the stand level to find the maximum value at risk (VaR, annualized net present value exceeded with probability of 0.99). Relevant uncertainties were integrated via Monte Carlo Simulation and bootstrapping. The results showed a maximum VaR for a highly diversified treatment combining 42 per cent Norway spruce and 58 per cent European beech and included area fractions with regeneration harvests from age 50 to 120 years. This treatment avoids clear-cutting and a mono-species forest composition. It uses tree species diversification and extends the regeneration period over 70 years to diversify hazard and price risks. The resulting scenario may be called ‘near-natural’ and emerges as the optimal choice, particularly for cautious, and thus risk-avoiding forest owners who do not have the opportunity to diversify risks by means of large-scale forest properties. [ABSTRACT FROM AUTHOR]