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.