Forest Edge Regrowth Typologies in Southern Sweden—Relationship to Environmental Characteristics and Implications for Management

Abstract

After two major storms, the Swedish Transport Administration was granted permission in 2008 to expand the railroad corridor from 10 to 20 m from the rail banks, and to clear the forest edges in the expanded area. In order to evaluate the possibilities for managers to promote and control the species composition of the woody regrowth so that a forest edge with a graded profile develops over time, this study mapped the woody regrowth and environmental variables at 78 random sites along the 610-km railroad between Stockholm and Malmö four growing seasons after the clearing was implemented. Through different clustering approaches, dominant tree species to be controlled and future building block species for management were identified. Using multivariate regression trees, the most decisive environmental variables were identified and used to develop a regrowth typology and to calculate species indicator values. Five regrowth types and ten indicator species were identified along the environmental gradients of soil moisture, soil fertility, and altitude. Six tree species dominated the regrowth across the regrowth types, but clustering showed that if these were controlled by selective thinning, lower tree and shrub species were generally present so they could form the “building blocks” for development of a graded edge. We concluded that selective thinning targeted at controlling a few dominant tree species, here named Functional Species Control, is a simple and easily implemented management concept to promote a wide range of suitable species, because it does not require field staff with specialist taxonomic knowledge.

Evaluation of Forest Edge Structure and Stability in Peri-Urban Forests

“…This poses a question on the structural changes influenced by cultivation measures and on how far into the interior forest area they reach. By comparing structural differences of forest edges at 10 m distances from the forest edge towards the interior forest area, we confirmed the findings of the researchers estimating that the structural changes in the forest edge are quite short, seldom exceeding 20 m [48]. In the area of Ljubljana, this applies to both groups of forest patches within the motorway ring road, namely Rožnik and Golovec.…”

“…At younger development stages of such forest edges, a selective thinning approach is recommended, as it enables the possibility to accelerate or promote a range of tree species [48].…”

“…The patches in Nadgorica (Figure 7) are an example of how the building of infrastructure (power line) causes the formation of new forest edges, which develop after large-scale human interventions. Several directions and guidelines are available for the management of such forest edges with emphasis on favourable dimension ratios (Figure 8), much like for roadside and railway corridors [11,16,48].…”