Boreal forests are vast ecosystems encompassing one-third of the world’s forested area. When covered by snow in the winter months, these forests have a peaceful and calming appearance, evoking feelings of wonder for their natural beauty and a sense of solitude amidst their vast stretches of wilderness. But appearances can be deceiving: although they seem tranquil on the surface, boreal forests are in reality undergoing profound changes.
Northern latitudes, where boreal forests occur, are particularly susceptible to the effects of climate change. This means that the biodiversity and carbon balance of these forests are being altered more rapidly and severely than those of their southern counterparts.
One example is the INFORMA case study in North Karelia (Lieksa), the easternmost region of Finland, led by the University of Eastern Finland. There, forests are dominated by Scots pine, which covers 93% of the forest area, followed by Norway Spruce (5,2%) and broadleaved trees (1,4%). Trees rely on long periods of frozen soil, which help anchor them to the ground during winter storms. The soil freeze period, however, is becoming shorter due to the warmer climate, which increases the occurrence of wind damage to forests – especially to the shallow-rooted species Norway spruce but also to Scots pine. Broadleaved trees are without leaves from late autumn to early spring – the windiest time of the year – and therefore suffer less wind damage.
Another climate impact suffered in the region are bark beetle outbreaks, which will likely become more frequent, affecting particularly Norway spruce trees. Such pest outbreaks may have cascading effects with wind damages, especially if wind-damaged trees are left in forests and not timely harvested, becoming a target of bark beetles.
Although forest regeneration and restoration can help reestablish disturbed forests, browsing of young trees by moose (especially of pine and broadleaves) prevents regeneration and is another typical forest management challenge in the region. Therefore, proper adaptive forest management practices are needed to tackle these challenges and enhance forest resilience to climate change.
Current forest management focuses on either timber production, recreation, or nature conservation, depending on the sub-area. The intensity of forest management ranges from relatively intensive to less intensive but also includes areas where no human intervention takes place. Where recreation plays a more pivotal role, management intensity is low. In this case, selective or gap cuttings are performed and forests have trees of different ages (uneven-aged forests). Forest management may even be completely abandoned. If nature conservation is the main aim, then no management measures are allowed. Where timber production is the focus, even-aged and uneven-aged forest management approaches are applied.
Boosting forest resilience in the area will involve increasing the proportion of mixed forests which are considered less vulnerable to natural hazards than coniferous monocultures. This could be done on sites where planted or seeded pine and planted spruce could grow together with each other or with naturally regenerated broadleaved trees. For example, on medium fertile sites, a mixture of pine, spruce and broadleaves forest might be created by simultaneously planting Norway spruce and seeding Scots pine and allowing naturally-born broadleaves to also grow there as a mixture. The increase of mixed forests can also be obtained by planting broadleaved species on medium fertile and fertile sites and letting coniferous (especially spruce) grow there naturally.
However, a major part of the study area is characterized by a low fertility soil type, where Scots pine has better growth performance than Norway spruce and broadleaves. Therefore, in these locations, Scots pine should be preferred as a main tree species.
INFORMA proposes spatially explicit portfolios of multipurpose forest management practices, considering the regional circumstances and targets set for forest management, as well as the need to adapt to and mitigate climate change. The resilience of forests and multifunctionality will be increased in a sustainable way by utilising stand-level information in forest simulation modelling and scenario analyses, and through diverse dissemination activities of research findings. This will provide decision makers such as forest managers, owners and forest authorities with science-based management options that cater for their needs and preferences in times of climate change.
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