Response of Boreal Jack Pine (Pinus banksiana Lamb.) Stands to a Gradient of Commercial Thinning Intensities, with and without N Fertilization

Abstract

This study examines tree and stand response to a gradient of commercial thinning intensities and nitrogen fertilization (200 kg N ha−1) in nine jack pine (Pinus banksiana) stands of Eastern Canada over a period of 14 years. Thinning intensity ranged from 0% basal area removal in control plots to 64% in thinned plots. Tree diameter increment, absolute and relative volume increment and mean volume increased with thinning intensity and were higher in fertilized plots. Individual tree response depended on tree diameter, with smallest trees exhibiting highest relative volume increment to thinning intensity. Stand basal area increment was positively associated to initial stand basal area and negatively to stand age. In thinned and fertilized plots, stand volume increment was higher and natural mortality lower than in fertilized only and unfertilized control plots over the 5–14 year period after thinning. However, the positive effect of fertilization on tree volume increment decreased with thinning intensity. Despite positive individual tree growth responses to thinning and fertilization, residual stand volume increment decreased with increased thinning intensity in both fertilized and unfertilized plots. While total cumulative stand volume (harvested + residual) also decreased with thinning intensity in unfertilized plots, comparable total volumes were observed in fertilized + thinned and unthinned control plots. Nitrogen fertilization in the years following commercial thinning enhanced the benefit of thinning on these relatively poor sites by increasing tree diameter growth, lowering mortality, and increasing total stand merchantable volume compared to unfertilized thinned stands.

Aboveground Carbon Content and Storage in Mature Scots Pine Stands of Different Densities

“…It was found that, immediately after thinning, there was a decrease in stand volume growth, typically lasting approximately 10 years, levelling off after this period [50]. In addition, the remaining trees had a greater volume increment if thinning was more intense [44,48,51].…”

Deterministic Models of Growth and Mortality for Jack Pine in Boreal Forests of Western Canada

“…High intensity fires can hinder regeneration [11], but medium intensity fires increase tree diversity and delay replacement by other species [12]. Pre-commercial thinning and fertilization improves tree growth [13,14], with the largest effect being observed for young trees [15] and represent potentially viable silvicultural investments [16]. Considering the ecological and economic importance of this species in the boreal forest, there is a need for improved knowledge on growth, yield and mortality of jack pine.…”

Twenty-five years post-treatment conifer responses to silviculture on aKalmia-dominated site in eastern Canada

“…Crop-species responses to silvicultural treatments vary, however, depending on key functional traits such as shadetolerance or nutrient requirements (Périé and Munson 2000, Wagner and Robinson 2006, Kranabetter et al 2017. For example, we recently observed that fast-growing, light-demanding jack pine (Pinus banksiana Lamb.)…”

“…BSP) responded linearly to this variable (Thiffault et al 2012b). Silvicultural treatments can also interact with each other, leading to multiplicative rather than additive responses of planted trees; for example, Nilsson and Örlander (2003) reported that fertilization significantly increased Norway spruce growth in the short-term when combined with herbicide application, but fertilization effects were not significant when competing vegetation was left untouched. Interactions between planted species and silvicultural treatments, and among silvicultural treatments, make it difficult to predict mid-and long-term impacts of reforestation strategies on stand productivity (Mason 1992), and there is thus a need to acquire and analyse long-term empirical data from silvicultural trials to inform the management decisions required for sustainable production of ecosystem services, including wood supply.…”

“…Soil scarification in boreal ecosystems disturbs the thick organic layer and exposes the mineral soil, thus increasing root zone temperatures, favouring better access to soil water, stimulating decomposition, and creating competition-free microsites (Örlander et al 1990(Örlander et al , Prévost 1992. Scarification ultimately reduces the planting stress of seedlings and results in increased early seedling survival and growth (Thiffault et al 2005).…”