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

Abstract

Abstract:The stand initiation stage decisively influences future forest structure and composition, particularly in the boreal forest which is a stand replacement disturbance driven system. In boreal Alaska, the conventional forest management paradigm has focused on the production of large-dimension timber, particularly white spruce (Picea glauca). However, energy generation and heating from wood is increasing, and is likely to significantly expand total forest harvest, further shifting management focus to fuelwood production. We evaluated the effects of forest harvest management practices on post-harvest regeneration by examining whether harvest type, site preparation method, and reforestation technique resulted in differences in forest regeneration in terms of species presence, dominance, basal area, and total stem biomass using a stochastic gradient boosting (TreeNet algorithm). We recorded diameter at breast height and height of white spruce, birch (Betula neoalaskana), and aspen (Populus tremuloides) in 726 plots from 30 harvest units, distributed across the various harvest and treatment types, harvest years, harvest sizes, and geographical locations. Our results indicate that management practices suitable/acceptable for woody biomass production differ from the more traditional dimensional timber production from white spruce-focused management. Artificial reforestation does not differ from natural regeneration in obtaining more stems or producing greater biomass. Clearcutting and site preparation increased tree regeneration, basal area, and woody biomass when compared to a partial harvest with no site preparation. Planting of white spruce in the Alaskan boreal forest may only be necessary in some specific circumstances, such as years with no/low white spruce seed crop, or in landscapes depleted of seed trees.

Perspectives on Sustainable Forest Management in Interior Alaska Boreal Forest: Recent History and Challenges

“…Timber harvest revenue is marginal, especially when demand is low, and forest resource management in general is expensive, mainly due to the large area and limited access. A recent study, however, found that natural regeneration is adequate after white spruce harvesting without reforestation [46,47]. It is also important to point out that natural regeneration may take longer to regenerate forest stands than artificial reforestation, but depending on the management goal, natural regeneration may be more suitable than artificial reforestation (e.g., when the goal is to create wildlife habitat).…”

Effects of substrate availability and competing vegetation on natural regeneration of white spruce on logged boreal mixedwood sites

“…(Lieffers et al 1993). For these reasons, postharvest regeneration of white spruce on boreal mixedwood sites is primarily achieved through planting of seedlings, because natural regeneration is considered to be too unpredictable (Martin-DeMoor et al 2010;Morimoto et al 2017). However, as the cost of reforestation is high relative to the value of the wood harvested in boreal forests, natural regeneration is an economically attractive alternative (Gärtner et al 2011).…”