Longer-Term Volume Trade-offs in Spruce and Jack Pine Plantations Following Various Conifer Release Treatments

Abstract

We assessed growth responses 10 years post treatment for 31 combinations of site, species, and treatments from six studies in Ontario, Canada, to determine if conifer release treatments increase gross total conifer volumes but decrease gross total stand volumes in boreal forests. Treatments included single and multiple herbicide application or motor-manual and mechanical conifer release. Treatment effects on 10 th -year gross total preferred conifer and total stand volumes ranged from -49% to +556% and -71% to +116%, respectively, compared to the untreated controls. We projected net merchantable stand volumes (NMV) from 10 years post treatment to 60 years of age. These projections indicate that NMV of preferred conifers at age 60 could range from 7.4 m 3 ha -1 to 232.4 m 3 ha -1 . The variation in observed and predicted volumes can be attributed to site characteristics, tree species, ecology, and treatment efficiency.Keywords: forest vegetation management, growth and yield, Picea mariana, Picea glauca, Pinus banksiana, herbicides, motor manual cutting résumé Nous avons analysé les réactions, en termes de croissance 10 ans après traitement, décrites dans six études effectuées en Ontario, au Canada, totalisant 31 combinaisons de stations, d' espèces et de traitements, afin de déterminer si les traitements de dégagement des conifères ont permis, en forêt boréale, un accroissement du volume brut total des conifères mais une diminution du volume brut total des peuplements. Les traitements comportaient une application simple et une application multiple de phytocide ou un dégagement au moyen d' outil motorisé individuel et un dégage-ment mécanisé. Les effets des traitements sur le volume brut total des conifères sélectionnés et sur le volume total des peuplements à la 10e année ont varié respectivement de -49% a +556% et de -71% à +116%, comparativement aux superficies témoins non traitées. Nous avons projeté les volumes marchands nets (VMN) des peuplements 10 ans après traitement jusqu'à l'âge de 60 ans. Ces projections indiquent que les VMN des conifères sélectionnés à l'âge de 60 ans pourraient varier de 7,4 m3 ha-1 à 232,4 m3 ha-1. Les variations entre les volumes mesurés et prédits peuvent être attribuées aux caractéristiques de la station, à l' espèce, à l' écologie et à l' efficacité du traitement.

Response of Breeding Songbirds to Vegetation Management in Conifer Plantations Established in Boreal Mixedwoods

“…The glyphosate (i.e., Vision) treatment was the most effective vegetation management practice on this site for releasing conifers (Bell et al 2011a, this issue), and did not cause any major shifts in presence/absence of songbird species. However, the fact that we were able to detect differences in relative abundance of bird species in the Visiontreated areas compared to the untreated areas 11 years post treatment suggests that short-term responses are not indicative of longer-term responses.…”

“…In this paper, which is one of a series of papers related to forest vegetation management published in the March/April 2011 issue of The Forestry Chronicle (see Bell et al 2011a), we report the response of bird communities 11 years post treatment on the Fallingsnow Ecosystem Project. We anticipated a several-year response of songbird community composition to vegetation management treatments due to the high philopatry that male songbirds sometimes show to their breeding sites (Hobson et al 2004).…”

Synthesis of Silviculture Options, Costs, and Consequences of Alternative Vegetation Management Practices Relevant to Boreal and Temperate Conifer Forests: Introduction

“…In short, results were influenced by site quality, initial stocking of preferred conifers, stem densities, treatment type, and application timing. Bell et al (2011a) suggest that it is unlikely that any one treatment will be universally effective and recommend that treatment choice be based on site and species ecology, treatment efficacy, and forest management objectives.…”

Modelling Landscape-level Effects of Reduced Herbicide Use in Two Forests in Northern Ontario

“…However, landscape-level implications and the indirect effects of herbicide reduction on forest management objectives related to wildlife habitat supply, quantity of old growth, wood supply, and forest management infrastructure (such as road networks) are less well known. While vegetation management alternatives may result in similar composition (Dampier et al 2006), growth rates (Bell et al 2011a), and wildlife habitat at the stand level (Lautenschlager et al 1997, Fortier et al 2005, Swift and Bell 2011, even subtle differences could equate to significant landscape-level changes when applied to millions of hectares over long periods.…”

“…Reductions in the use of herbicides are generally countered by increased use of alternatives and/or practices such as planting large stock, leaving advanced regeneration, or adopting a less intensive treatment package (McCarthy et al 2010, Thiffault andRoy 2010). The direct, stand-level silvicultural effects (e.g., lower yields of some conifers, increased hardwood from sprouting, more hardwood cull) resulting from vegetation management alternatives such as motor-manual tending (brush saw treatments) have recently been summarized (Bell et al 2011a, this issue, Homagain et al 2011, this issue, Wiensczyk et al 2011). However, landscape-level implications and the indirect effects of herbicide reduction on forest management objectives related to wildlife habitat supply, quantity of old growth, wood supply, and forest management infrastructure (such as road networks) are less well known.…”