Natural Regeneration of the Tree Stand in the Bilberry Spruce Forest—Clear-Cutting Ecotone Complex in the First Post-Logging Decade

Abstract

Bilberry spruce forests are the most widespread forest type in the European boreal zone. Limiting the clear-cuttings size leads to fragmentation of forest cover and the appearance of large areas of ecotone complexes, composed of forest (F), a transition from forest to the cut-over site under tree canopy (FE), a transition from forest to the cut-over site beyond tree canopy (CE), and the actual clear-cut site (C). Natural regeneration of woody species (spruce, birch, rowan) in the bilberry spruce stand—clear-cut ecotone complex was studied during the first decade after logging. The effects produced by the time since cutting, forest edge aspect, and the ground cover on the emergence and growth of trees and shrubs under forest canopy and openly in the clear-cut were investigated. Estimating the amount and size of different species in the regeneration showed FE and CE width to be 8 m—roughly half the height of first-story trees. Typical forest conditions (F) feature a relatively small amount of regenerating spruce and birch. The most favorable conditions for natural regeneration of spruce in the clear-cut—mature bilberry spruce stand ecotone are at the forest edge in areas of transition both towards the forest and towards the clear-cut (FE and CE). Clear-cut areas farther from the forest edge (C) offer an advantage to regenerating birch, which grows densely and actively in this area.

Microhabitat Conditions Influencing Ground Vegetation Dominants in an Ecotone between a Spruce (Picea abies (L.) H.Karst.) Forest and Clear-Cut Site during Ten Post-Logging Years

“…To interpret the effects of the factors in different EC zones correctly, we need to understand the differences between the zones. In our previous publications, we characterized the ECs in terms of tree regeneration amounts and microclimate parameters (irradiance and surface air temperature) [8,16].…”

“…However, as cowberry is ecologically a heliophyte [27] and physiologically better adapted than bilberry to relatively high insolation, its recovery was faster than in bilberry [28]. Cowberry abundance peaked in the 3rd-5th post-logging years but declined notably 10 years after logging (Table 4), apparently due to the regeneration-and understory layer forming in the surveyed clear-cut sites [16]. Abundant plant litter and grasses in zones CE and C reduced the percentage cover of cowberry.…”

“…Surveys were carried out in the adjoining communities of a bilberry-type spruce forest and a wavy hair-grass-dominated clear-cut site (2 to 10 years after clear-cutting) constituting an ecotone complex (EC) (Figure 1a). Characteristics of the spruce stands and clear-cuts were given in our previous publication [16]. Based on the results of previous studies [16,17], we assumed the transitional zone to be 8 m wide on each side of the forest/clear-cutting interface.…”

“…Characteristics of the spruce stands and clear-cuts were given in our previous publication [16]. Based on the results of previous studies [16,17], we assumed the transitional zone to be 8 m wide on each side of the forest/clear-cutting interface. The ground vegetation was studied in 40-50 m long transects running from inside the forest into the clear-cut site (20-25 m into each of the forest and the clear-cut site).…”

“…The microclimate change, however, also extends beyond the actual clear-cut site to the forest strip along the clear-cutting edge [4][5][6][7]. A finding in boreal coniferous forests is that solar irradiation, air humidity and temperature changed the most significantly, with the closest approximation to the background conditions under the forest canopy, at a distance of some 8 m from the clear-cutting edge into the forest [8,9].…”