Success Factors for Experimental Partial Harvesting in Unmanaged Boreal Forest: 10-Year Stand Yield Results

Louiza Moussaoui,Alain Leduc,Nicole J. Fenton,Yves Bergeron,Annie Claude Bélisle,Miguel Montoro Girona,Benoit Lafleur

doi:10.3390/f11111199

Abstract

Over the past two decades, partial harvesting has been increasingly used in boreal forests as an alternative to clearcutting to promote irregular stand structures and maintain a balance between biodiversity preservation and continued timber production. However, relatively little is still known about the silvicultural potential of partial harvesting in Canada’s boreal forest, especially in areas prone to organic matter accumulation (paludification), and most prior research has focused on biodiversity responses. In this study, we assess the effects of partial harvesting on stand development (recruitment, growth, and mortality) ten years after harvesting in previously unmanaged black spruce stands and quantify its effectiveness in reducing the impacts on ecosystem structures. Our analyses revealed that pre-harvest stand structure and site characteristics, especially initial basal area, sapling density, tree diameter, and organic layer thickness (OLT) were major factors involved in stand development ten years following these partial harvesting treatments. Depending on pre-harvest structure and site characteristics, partial harvesting can result in either an increase in post-harvest tree recruitment and growth or a loss of stand volume because of standing tree mortality. To increase the chances of partial harvesting success in ensuring an increase in decennial stand yield after harvest in black spruce forest stands, sites prone to paludification (i.e., where OLT >17 cm) should be left unharvested. This study illustrates the importance of taking into account pre-existing structure and site characteristics in the selection of management strategies to maximize the potential of partial harvesting to achieve sustainable forest management in black spruce stands.

Highlights

In recent decades, the use of forestry practices other than clearcutting has been explored as a means to mitigate the major issues facing sustainable management of boreal forests, i.e., the impacts on ecosystem structures, functions and dynamics, and the preservation of biodiversity [1,2,3,4,5]
One-third (33%) of the sampling plots had a reduction in basal area ten years after partial harvesting, whereas a gain in basal area was recorded for 60% of the plots (Figure 2)
Net stand yield significantly increased with the growth of residual trees and the post-harvest recruitment into the merchantable tree class, whereas it significantly decreased with increasing residual tree mortality (Figure 3)

Summary

Introduction

The use of forestry practices other than clearcutting has been explored as a means to mitigate the major issues facing sustainable management of boreal forests, i.e., the impacts on ecosystem structures, functions and dynamics, and the preservation of biodiversity [1,2,3,4,5]. Ecosystem management proposes partial harvesting as an alternative management strategy to clearcutting regimes to reduce the differences between natural and managed forests to create landscapes that contain all of the diversity and heterogeneity of the natural forest [10] Both in North America and Europe, partial harvesting has been proposed to promote the maintenance of some favorable stand structural attributes for a variety of boreal forest flora and fauna [11,12,13,14,15]. Viable economic yields of timber from partial harvesting require that most retained trees survive and grow rather than being lost to windthrow shortly after harvest This contributes to the maintenance of habitat conditions over the long-term, especially for species associated with irregular and uneven-sized structures of old-growth boreal forests [18,19,20,21,22]

Objectives

Methods

Results

Discussion

Conclusion