Effects of competing vegetation on juvenile white spruce (Picea glauca (Moench) Voss) growth in Alaska

Abstract

-We examined the impacts of competing vegetation on survival and juvenile growth of white spruce (Picea glauca (Moench) Voss) on 3 units in south-central Alaska and on 3 units in interior Alaska. Treatments consisted of herbicide site preparation and release treatments, and also included a treatment in which competition was minimized for 5 years (weed-free treatment). At all units, the weed-free treatment resulted in significant increases in white spruce height and basal diameter by ages 10 or 11 compared to untreated plots. Average heights and diameters in the weed-free treatments were 1.5 to 3.8 times and 2.0 to 3.8 times those in the untreated plots, respectively. Results from the other treatments differed by unit based on the efficacy of a particular treatment on the vegetation at that unit. For all units, regression equations indicated a significant decrease in diameter at year 10 or 11 with increasing competitive cover and overtopping.

Juvenile stand responses and potential outcomes of conifer release efforts on Alberta's spruce–aspen mixedwood sites

“…Among these are two studies in spruce (Sutton 1995, Daggett 2003 and one in balsam fir (Maclean and Morgan 1983) that have shown positive 30-year responses in the northeast. There are, however, a growing number of studies recently published that clearly illustrate positive effects five to 10 years after treatment, consistent with our study observations (e.g., Harper et al 1997;Biring et al 1999;Pitt et al 1999Pitt et al , 2000Pitt et al , 2004Bedford et al 2000;Bell et al 2000;Biring and Hays-Byl 2000;Boateng et al 2000;Cole et al 2003).…”

“…Planted spruce are unlikely to be well positioned relative to canopy gaps, except by chance, and may suffer greater losses than MGM suggests. Work in Alaska indicates that white spruce suppressed early by aspen exhibit long periods of very poor growth and will likely contribute little to future mixedwood structure (Cole et al 2003). Our plantation data may therefore exceed the model's scope, potentially resulting in both absolute and relative prediction errors; the general behaviour of the model may not represent what would actually occur.…”

Clearcutting and Site Preparation, but Not Planting, Promoted Early Tree Regeneration in Boreal Alaska

“…Site preparation has been widely demonstrated to enhance seedbed quality for tree regeneration [73,78], thus promoting more vigorous trees that can achieve higher rates of both below-and above-ground growth. Several experimental studies in Interior Alaska have reported that site preparation results in higher density and/or growth of white spruce [2,3,5,79], and in the boreal forest of Canada [22,80]. Our study now establishes that these gains are also achieved in operational practices up to 40 years following harvest.…”

Early vegetation control for the regeneration of a single-cohort, intimate mixture of white spruce and aspen on upland boreal sites – 10thyear update

“…Research and operational experience have shown that fairly rigorous vegetation management is required to counter the natural propensity of upland boreal sites to regenerate aspen following harvest (Wood and von Althen 1993, Cole et al 2003, Pitt and Bell 2005, Boateng et al 2006 and that unintentional, intimate mixedwoods are often the result of conventional conifer regeneration efforts (Navratil et al 1991, Pitt et al 2004a2004b, Pitt andBell 2005). In 2000, we worked with a coalition of forest industry partners to formulate and test a practical regeneration strategy for a singlecohort, intimate mixture of spruce and aspen that would capitalize on the natural propensity of these sites to regenerate aspen following harvest.…”