Residual Stand Damage under Different Harvesting Methods and Mitigation Strategies

Abstract

A major component of sustainable forest management are the stands left behind after the logging operation. Large mechanized harvesting equipment involved in current forest management can inflict damage on residual trees; and can pose a risk of mortality from diseases, natural calamities, and/or degrade future economic value. The primary objective of this study was to evaluate the residual stand damage under different harvesting methods and silvicultural prescriptions i.e., crop tree release (CTR), diameter limit cut (DLC), and overstory removal (OSR). The second objective was to evaluate the intensity and frequency of damage occurring on the bole, canopy, and root at tree and stand level. The third objective was to document strategies adopted globally to minimize stand damage due to timber harvesting. Five harvest blocks implementing three silvicultural prescriptions, were selected as the treatments across two different industrial timberlands in central and northern Maine (Study Site (SS) I and II, respectively). A hybrid cut-to-length (Hyb CTL) and whole-tree (WT) harvesting method were employed for conducting the harvest in SS I and II, respectively. Systematic transect sampling was employed to collect information on type, frequency, and intensity of damages. The inventory captured 41 and 8 damaged trees per hectare with 62 and 22 damages per hectare from SS I and SS II respectively. Bole damage was the most frequent damage across all treatments. The Hyb CTL had lower damage density (damage per ha) and severity compared to WT. The average number of trees damaged per ha was higher for CTR prescriptions compared to DLC. There were no significant differences in the height of the damages from the ground level between treatments within each study site; however, there was a significant difference between the study sites. Species damaged was directly related to the residual trees left behind and was dominated by American beech, yellow birch, sugar maple, and eastern hemlock. Finally, the study provides strategies that can be adopted at different forest managerial phases to mitigate residual stand damage.

Assessing the Residual Stand Damage after Thinning with Different Levels of Mechanization

“…Similar results were obtained by Magagnotti et al [23]. Akay et al [24], Cudzik et al [5], Kizha et al [7], and Suhartana et al [25] reported that the most damage occurs during tree felling and extraction by machine traffic and log dragging and loading from the stump to the landing. Hwang et al [6] found that residual stand damage was between 16.2% and 32.2%, and damaged trees were closed near forwarding trails with injuries near the ground where mechanical thinning operations were practiced.…”

“…Damage to 23% and 11% of residual trees due to skidding and winching operations, respectively, were reported by Borz et al [10] and Hartsouth [11]. Most of the tree damages are observed close to the extraction trails [7,12]. The amount or level of damage to residual trees depends on several factors, including working conditions (tree species and density [2,13,14]), harvesting method (level of mechanization and thinning type [7]), harvesting system (cut-to-length and whole-tree [5,6]), and operator experience and skills [6,15].…”

“…In many cases, mechanized harvesting systems have been applied to thinning operations because they are effective technologies for improving productivity and work safety [4][5][6]. However, felling and extraction operations can adversely affect the remaining trees [4,7]. For example, Ursic et al [4], Kizha et al [7], and Han [8] reported that thinning operations are a crucial cause of declining standing tree growth and increased pests and diseases, resulting in lower wood quality.…”

“…However, felling and extraction operations can adversely affect the remaining trees [4,7]. For example, Ursic et al [4], Kizha et al [7], and Han [8] reported that thinning operations are a crucial cause of declining standing tree growth and increased pests and diseases, resulting in lower wood quality. Thus, damage to residual trees is a critical consideration in the planning and implementation of thinning operations.…”

“…Most of the tree damages are observed close to the extraction trails [7,12]. The amount or level of damage to residual trees depends on several factors, including working conditions (tree species and density [2,13,14]), harvesting method (level of mechanization and thinning type [7]), harvesting system (cut-to-length and whole-tree [5,6]), and operator experience and skills [6,15]. In addition, damaged trees are concentrated close to felling, skidding, and forwarding trails at a height of less than 1 m, owing to machine movement, tree processing, and handling [6,16,17].…”