Canadian Forest Service Publications
Young and old forest in the boreal: critical stages of ecosystem dynamics and management under global change. 2018. Kuuluvainen, T.; Gauthier, S. For. Ecosyst. 5: 26.
Issued by: Laurentian Forestry Centre
Catalog ID: 39200
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The circumboreal forest encompasses diverse landscape structures, dynamics and forest age distributions determined by their physical setting, and historical and current disturbance regimes. However, due to intensifying forest utilisation, and in certain areas due to increasing natural disturbances, boreal forest age-class structures have changed rapidly, so that the proportion of old forest has substantially declined, while that of young post-harvest and post-natural-disturbance forest proportions have increased. In the future, with a warming climate in certain boreal regions, this trend may further be enhanced due to an increase in natural disturbances and large-scale use of forest biomass to replace fossil-based fuels and products.
The major drivers of change of forest age class distributions and structures include the use of clearcut short-rotation harvesting, more frequent and severe natural disturbances due to climate warming in certain regions. The decline in old forest area, and increase in managed young forest lacking natural post-disturbance structural legacies, represent a major transformation in the ecological conditions of the boreal forest beyond historical limits of variability. This may introduce a threat to biodiversity, ecosystem resilience and long-term adaptive capacity of the forest ecosystem.
To safeguard boreal forest biodiversity and ecosystem functioning, and to maintain the multiple services provided to societies by this forest biome, it is pivotal to maintain an adequate share and the ecological qualities of young post-disturbance stages, along with mature forest stages with old-growth characteristics. This requires management for natural post-disturbance legacy structures, and innovative use of diverse uneven-aged and continuous cover management approaches to maintain critical late-successional forest structures in landscapes.
Plain Language Summary
In order to protect the biodiversity and functioning of boreal forest ecosystems and to maintain the multiple services provided to society by that forest environment, it is essential to maintain the ecological qualities and an adequate share of young forest stages after disturbances as well as older forests. With respect to young forest stages, the authors emphasize that this requires management strategies that maintain the biological legacies created by natural disturbances. With respect to older forests, the innovative use of various forest management approaches promoting the conservation of several age and size classes could help maintain forest structures that represent late forest stages in landscapes.
Increased forest use and the increased occurrence of natural disturbances have rapidly changed the age-class structure of the boreal forest. The proportion of old-growth forests has decreased, while that of young forests resulting from harvest or natural disturbances has increased. Forest management aimed at preserving the characteristics of these different forest stages helps maintain a diversity of potential responses to uncertain future conditions stemming, among other things, from global warming.