Environmental controls on seedling establishment in a boreal forest: implications for Scots pine regeneration in continuous cover forestry
Häggström, B., M.J. Gundale and A. Nordin. 2023.
Abstract
In nutrient poor and dry forest sites common to northern Scandinavia, Scots pine (
Pinus sylvestris L.) is the
most common species both in managed and natural forests. However, Scots pine is sensitive to competition
during establishment. Harvesting of all trees within a given area, i.e., clear-cutting, liberates regenerating
seedlings from competition with mature trees. However, recent debates are in favor of clear-cut-free, i.e.,
continuous cover forestry (CCF). When choosing management method, it is important to recognize how
competitive interactions direct the success of Scots pine regeneration. We studied Scots Pine regeneration
at three environments: beneath the canopy of mature trees, at the canopy edge in full sunlight, and distant
from the canopy with no inuence of mature trees. We imposed three treatments in each of these
environments: root isolation (i.e., trenching), nitrogen (N) fertilization, and control plots. Root isolation
enhanced seedling performance under the canopy of mature trees. N fertilization enhanced seedling
performance to a greater extent in the clear-cut than at the forest edge. However, N fertilization had no effect
under the canopy. In the N fertilized plots we measured higher N content in the soil under the canopy than in
the open environments, indicating that not all excess N was obtained by the mature trees. N-uptake might
have been limited by competition for water in the N fertilized plots. Our results suggest that belowground
competition limits the success of regeneration of Scots pine. However, N fertilization presents a tool to
compensate for underground competition along canopy edges.
Key Words
Continuous cover forestry, Scots pine, tree regeneration, belowground competition, clear-cutting, forest growth
