Effects of timing of glyphosate application on jack pine, black spruce, and white spruce plantations in northern Manitoba

Abstract

Deferring conifer release treatments is sometimes necessary, but its effects on crop tree performance are not well understood. We investigated the effects of deferring glyphosate applications on jack pine (Pinus banksiana Lamb.), black spruce (Picea mariana [Mill.] BSP), and white spruce (Picea glauca [Moench.] Voss.) plantations established on a dry site with moderate competition and a moist site with heavier competition in The Pas, northern Manitoba. At each site, experimental treatments included no herbicide and one glyphosate (formulated as Vision ® ) at 1.42 kg acid equivalent glyphosate ha -1 application between one and five years after planting with three replications. Survival, root collar diameter, and height of the three conifers were repeatedly measured for ten consecutive years following planting. Survival of the three conifers was not affected by glyphosate application. For all the three species, root collar diameter and stand volume of crop trees increased significantly in glyphosate-treated plots, compared to control plots. Varying the timing of glyphosate application between year 1 and 5 resulted in a similar conifer dimensions. Glyphosate application significantly improved height growth of black spruce and marginally white spruce, but not jack pine. On these sites, glyphosate reduced the cover of woody species, but grass, forbs and shrubs rapidly captured the newly available growing space. A two variable regression analysis revealed that grass cover negatively affected stand volume of all three conifer species. Cover of tall shrub, forbs, and interaction of cover and height of tall shrubs were the next most important variables to explain jack pine, black spruce, and white spruce volume growth, respectively.Key words: vegetation management, forest herbicides, survival, growth, stand volume, long-term repeated measurements RÉSUMÉ Le report des traitements de dégagement des conifères est parfois nécessaire, mais ses effets sur la performance des arbres à récolter ne sont pas bien connus. Nous avons étudié les effets du report des applications glyphosate dans le cas de plantations de pin gris (Pinus banksiana Lamb.), d'épinette noire (Picea mariana [Mill.] BSP) et d'épinette blanche (Picea glauca [Moench.] Voss.) établies sur station sèche ayant un niveau modéré de compétition et sur station humide avec une compétition plus accentuée dans la région de The Pas dans le nord du Manitoba. Pour chaque station, les traitements expérimentaux comprenaient un témoin et une application de 1,42 kg ha -1 d'agent équivalent de glyphosate (selon la formule Vision®) entre un et cinq ans après plantation, le tout selon trois reproductions. La survie, le diamètre de la racine au collet et le volume du peuplement constitué d'arbres à récolter ont été mesurés pendant dix années consécutives après la plantation. La survie des trois espèces de conifères n'a pas été affectée par l'application de glyphosate. Pour les trois espèces, le diamètre de la racine au collet et le volume du peuplement constitué d'arbres à ...

Large Planting Stock Type and Mechanical Release Effects on the Establishment Success ofPicea glaucaPlantations in Quebec, Canada

“…But, after eight growing seasons, REL5 seedlings had yet to catch up with REL3 seedlings in terms of absolute dimensions, even though the height and diameter differences could be considered of limited silvicultural impact. These results differ slightly from those reported by Fu et al [46], who compared tenth-year effects of delayed aerial glyphosate applications from year 1 to 5: at the end of their experiment, all treatments had produced similar-sized saplings. As illustrated in Figure 7, REL3 provided the crop-trees with ∼85% full sunlight during at least two seasons (4 and 5) during which REL5 seedlings continued to receive <60%PAR.…”

“…Nevertheless, the height/diameter ratios remained well below critical levels for plantation stability [3], even in control plots. Concomitant with the general pattern observed elsewhere (e.g., [46,47]), resource competition by noncrop species had limited influence on seedling survival in the short term. However, competition pressure in control plots is expected to induce mortality in the longer term, compared to treated plots [48], which, in turn, will have a significant impact on crop-tree production [49].…”

“…The study area is located in south central Quebec (46 • 43 06 N; 73 • 16 10 W) and is part of the sugar maple (Acer saccharum Marsh. )-yellow birch (Betula alleghaniensis Britt.)…”

Plant Community Diversity and Tree Growth Following Single and Repeated Glyphosate Herbicide Applications to a White Spruce Plantation

“…Results from studies in eastern Canada indicate that conifers generally show greater growth responses to early (e.g., site preparation before tree planting) treatments than to delayed treatments [14,15]. However, a study in Manitoba, Canada, showed no effects of age of treatment (between 1 and 5 years after planting) on growth of white spruce, black spruce, or jack pine resulting from a single aerial application [16]. In this experiment, the response was attributed to the replacement of woody vegetation by herbs and grasses following a single herbicide treatment [16].…”

Optimization of early cleaning and precommercial thinning methods in juvenile stand management of Norway

“…Vigorously growing competing vegetation can negatively affect site conditions and factors such as water availability (Nilsson et al 1996;Nilsson & Örlander 1999), nutrients (Nilsson et al 1996;Jobidon 2000), light (Nilsson et al 1996;Jobidon 2000), and temperature (Jobidon et al 2003). It is well known that high stocking densities of hardwoods can critically hinder the growth of the more desirable conifer trees (Walfridsson 1976;Folkesson & Bärring 1982;Andersson 1993;Jobidon 2000;Fu et al 2008;Bataineh et al 2013). Fierce competition from competing vegetation can eventually cause crop-tree mortality (Jobidon 2000).…”