Potentials of Natural Tree Regeneration after Clearcutting in Subalpine Forests

Abstract

Regeneration of interior mountain forests still is not adequately understood, although these forests are subject to intensified use over the last decades. We examined factors influencing the success of natural tree regeneration after harvesting in the Engelmann spruce–subalpine fir zone of the Monashee Mountains, British Columbia, Canada. Distance from the forest edge was an important factor for regeneration; at distances exceeding 70 m from the forest edge only 50% of plots showed sufficient natural regeneration to meet stocking targets compared with 90% of plots closer to forest edges. Seedling density and growth were superior in the more protected southern portions of clearcuts. Seedling growth was less in plots containing high cover of downed woody debris. There was no relationship between understory plant diversity or composition and tree seedling regeneration. However, cover of fireweed (Epilobium angustifolium) had a significant negative relationship with density but not growth of tree seedlings, particularly for lodgepole pine (Pinus contorta var. latifolia). Cover of fireweed decline substantially within the first 10 years after clearcutting. We conclude that natural regeneration of trees has potential to help achieve stocking targets and also to maintain natural diversity of tree species if spatial constraints, especially thresholds in clearcut size, are considered.

Langzeitforschung auf Sturmflächen zeigt Potenzial und Grenzen der Naturverjüngung

“…Die auf den SBF im Jahr 2010 erreichten Verjüngungsdichten (Abbildung 5) bewegen sich, mit Ausnahmen, am unteren Rand von Werten, die in Sturmflächen in Kanada, den USA, im russischen Ural und in Deutschland festgestellt werden konnten, wo sechs bis zehn Jahre nach einem Sturm zwischen 4800 und 20 200 Bäumchen pro Hektare standen (Cooper-Ellis et al 1999, Močalov & Lässig 2002, Kreyling et al 2008. Auf 12 bis 20 Jahre alten Sturmflächen in den USA und in Deutschland variierten die Dichten zwischen 995 und über 50 000 Individuen pro Hektare (Arévalo et al 2000, Zhao et al 2006, Keidel et al 2008, Palik & Kastendick 2009, Fischer & Fischer 2012.…”