European primary forest database v2.0.

Primary forests, defined here as forests where the signs of human impacts, if any, are strongly blurred due to decades without forest management, are scarce in Europe and continue to disappear. Despite these losses, we know little about where these forests occur. Here, we present a comprehensive geodatabase and map of Europe's known primary forests. Our geodatabase harmonizes 48 different, mostly field-based datasets of primary forests, and contains 18,411 individual patches (41.1 Mha) spread across 33 countries. When available, we provide information on each patch (name, location, naturalness, extent and dominant tree species) and the surrounding landscape (biogeographical regions, protection status, potential natural vegetation, current forest extent). Using Landsat satellite-image time series (1985-2018) we checked each patch for possible disturbance events since primary forests were identified, resulting in 94% of patches free of significant disturbances in the last 30 years. Although knowledge gaps remain, ours is the most comprehensive dataset on primary forests in Europe, and will be useful for ecological studies, and conservation planning to safeguard these unique forests.

Climate change induces multiple risks to boreal forests and forestry in Finland: A literature review.

Climate change induces multiple abiotic and biotic risks to forests and forestry. Risks in different spatial and temporal scales must be considered to ensure preconditions for sustainable multifunctional management of forests for different ecosystem services. For this purpose, the present review article summarizes the most recent findings on major abiotic and biotic risks to boreal forests in Finland under the current and changing climate, with the focus on windstorms, heavy snow loading, drought and forest fires and major insect pests and pathogens of trees. In general, the forest growth is projected to increase mainly in northern Finland. In the south, the growing conditions may become suboptimal, particularly for Norway spruce. Although the wind climate does not change remarkably, wind damage risk will increase especially in the south, because of the shortening of the soil frost period. The risk of snow damage is anticipated to increase in the north and decrease in the south. Increasing drought in summer will boost the risk of large-scale forest fires. Also, the warmer climate increases the risk of bark beetle outbreaks and the wood decay by Heterobasidion root rot in coniferous forests. The probability of detrimental cascading events, such as those caused by a large-scale wind damage followed by a widespread bark beetle outbreak, will increase remarkably in the future. Therefore, the simultaneous consideration of the biotic and abiotic risks is essential.

Factors controlling the evaporation of secondary organic aerosol from α-pinene ozonolysis.

Secondary organic aerosols (SOA) forms a major fraction of organic aerosols in the atmosphere. Knowledge of SOA properties that affect their dynamics in the atmosphere is needed for improving climate models. By combining experimental and modeling techniques, we investigated the factors controlling SOA evaporation under different humidity conditions. Our experiments support the conclusion of particle phase diffusivity limiting the evaporation under dry conditions. Viscosity of particles at dry conditions was estimated to increase several orders of magnitude during evaporation, up to 109 Pa s. However, at atmospherically relevant relative humidity and time scales, our results show that diffusion limitations may have a minor effect on evaporation of the studied α-pinene SOA particles. Based on previous studies and our model simulations, we suggest that, in warm environments dominated by biogenic emissions, the major uncertainty in models describing the SOA particle evaporation is related to the volatility of SOA constituents.

Applying a framework for landscape planning under climate change for the conservation of biodiversity in the Finnish boreal forest.

Conservation strategies are often established without consideration of the impact of climate change. However, this impact is expected to threaten species and ecosystem persistence and to have dramatic effects towards the end of the 21st century. Landscape suitability for species under climate change is determined by several interacting factors including dispersal and human land use. Designing effective conservation strategies at regional scales to improve landscape suitability requires measuring the vulnerabilities of specific regions to climate change and determining their conservation capacities. Although methods for defining vulnerability categories are available, methods for doing this in a systematic, cost-effective way have not been identified. Here, we use an ecosystem model to define the potential resilience of the Finnish forest landscape by relating its current conservation capacity to its vulnerability to climate change. In applying this framework, we take into account the responses to climate change of a broad range of red-listed species with different niche requirements. This framework allowed us to identify four categories in which representation in the landscape varies among three IPCC emission scenarios (B1, low; A1B, intermediate; A2, high emissions): (i) susceptible (B1 = 24.7%, A1B = 26.4%, A2 = 26.2%), the most intact forest landscapes vulnerable to climate change, requiring management for heterogeneity and resilience; (ii) resilient (B1 = 2.2%, A1B = 0.5%, A2 = 0.6%), intact areas with low vulnerability that represent potential climate refugia and require conservation capacity maintenance; (iii) resistant (B1 = 6.7%, A1B = 0.8%, A2 = 1.1%), landscapes with low current conservation capacity and low vulnerability that are suitable for restoration projects; (iv) sensitive (B1 = 66.4%, A1B = 72.3%, A2 = 72.0%), low conservation capacity landscapes that are vulnerable and for which alternative conservation measures are required depending on the intensity of climate change. Our results indicate that the Finnish landscape is likely to be dominated by a very high proportion of sensitive and susceptible forest patches, thereby increasing uncertainty for landscape managers in the choice of conservation strategies.

Spatially dynamic forest management to sustain biodiversity and economic returns.

Production of marketed commodities and protection of biodiversity in natural systems often conflict and thus the continuously expanding human needs for more goods and benefits from global ecosystems urgently calls for strategies to resolve this conflict. In this paper, we addressed what is the potential of a forest landscape to simultaneously produce habitats for species and economic returns, and how the conflict between habitat availability and timber production varies among taxa. Secondly, we aimed at revealing an optimal combination of management regimes that maximizes habitat availability for given levels of economic returns. We used multi-objective optimization tools to analyze data from a boreal forest landscape consisting of about 30,000 forest stands simulated 50 years into future. We included seven alternative management regimes, spanning from the recommended intensive forest management regime to complete set-aside of stands (protection), and ten different taxa representing a wide variety of habitat associations and social values. Our results demonstrate it is possible to achieve large improvements in habitat availability with little loss in economic returns. In general, providing dead-wood associated species with more habitats tended to be more expensive than providing requirements for other species. No management regime alone maximized habitat availability for the species, and systematic use of any single management regime resulted in considerable reductions in economic returns. Compared with an optimal combination of management regimes, a consistent application of the recommended management regime would result in 5% reduction in economic returns and up to 270% reduction in habitat availability. Thus, for all taxa a combination of management regimes was required to achieve the optimum. Refraining from silvicultural thinnings on a proportion of stands should be considered as a cost-effective management in commercial forests to reconcile the conflict between economic returns and habitat required by species associated with dead-wood. In general, a viable strategy to maintain biodiversity in production landscapes would be to diversify management regimes. Our results emphasize the importance of careful landscape level forest management planning because optimal combinations of management regimes were taxon-specific. For cost-efficiency, the results call for balanced and correctly targeted strategies among habitat types.

Moose (Alces alces) reacts to high summer temperatures by utilizing thermal shelters in boreal forests - an analysis based on airborne laser scanning of the canopy structure at moose locations.

The adaptation of different species to warming temperatures has been increasingly studied. Moose (Alces alces) is the largest of the ungulate species occupying the northern latitudes across the globe, and in Finland it is the most important game species. It is very well adapted to severe cold temperatures, but has a relatively low tolerance to warm temperatures. Previous studies have documented changes in habitat use by moose due to high temperatures. In many of these studies, the used areas have been classified according to how much thermal cover they were assumed to offer based on satellite/aerial imagery data. Here, we identified the vegetation structure in the areas used by moose under different thermal conditions. For this purpose, we used airborne laser scanning (ALS) data extracted from the locations of GPS-collared moose. This provided us with detailed information about the relationships between moose and the structure of forests it uses in different thermal conditions and we were therefore able to determine and differentiate between the canopy structures at locations occupied by moose during different thermal conditions. We also discovered a threshold beyond which moose behaviour began to change significantly: as day temperatures began to reach 20 °C and higher, the search for areas with higher and denser canopies during daytime became evident. The difference was clear when compared to habitat use at lower temperatures, and was so strong that it provides supporting evidence to previous studies, suggesting that moose are able to modify their behaviour to cope with high temperatures, but also that the species is likely to be affected by warming climate.

Phenological variation as protection against defoliating insects: the case of Quercus robur and Operophtera brumata.

Phenological synchrony between budburst and emergence of larvae is critical for the fitness of many spring-feeding insect herbivores. Therefore, large intraspecific variation in timing of budburst of the host may have a negative effect on the herbivore. We studied how asynchrony between emergence of larvae and budburst affects the fitness of Operophtera brumata (Lepidoptera: Geometridae), a major defoliator of Quercus robur, which can adapt to the phenology of a single tree. It is known that, in maturing leaves of Q. robur, accumulation of condensed tannins has a negative effect on growth of O. brumata. However, there is no information about the effect of hydrolysable tannins and other phenolics that are potential antifeedants. In this study, we also analysed changes in secondary chemistry of the foliage of Q. robur and how different compounds are correlated with growth and survival of O. brumata. The effect of asynchrony on O. brumata was studied in rearing experiments. The neonate larvae were incubated without food for different periods of time. The decline in nutritional quality of foliage was estimated by rearing cohorts of larvae with manipulated hatching times on the leaves of ten individual Q. robur trees. For the chemical analysis, the foliage of these trees was sampled at regular intervals. In the absence of foliage, mortality of neonate larvae started to increase exponentially soon after the larvae emerged. If the larvae missed budburst, the decline in nutritional quality of the foliage led to increased mortality and lower body mass (= fecundity). Hydrolysable tannins were not significantly correlated with performance of the larvae. Only condensed tannins were found to correlate negatively with the growth and survival of O. brumata. Certain individual trees were unsuitable hosts for O. brumata because the decline in quality of the foliage was very rapid. Based on regression equations for increasing rate of mortality and decreasing fecundity, we calculated that a relatively small mismatch of +/-30 degree days between budburst and hatching of larvae leads to a 50% decrease in the fitness of O. brumata. Thus, large phenological variation within a Q. robur stand can limit the colonisation of neighbouring trees by dispersing larvae. Furthermore, the hybridisation of moths adapted to phenologically different trees may lead to maladapted phenology of their offspring.