Abstract
Background: The frequency of wounded trees and intensity of wounds during logging operations can have serious impacts on stand growth and forest sustainability. The aims of the study were to evaluate and compare stand (tree and regeneration) damage level, wound characteristics, and damage types occurring when using a cable skidder in salvage logging and selection cutting.
 Methods: This study was conducted on four sites of mixed uneven-aged hardwood stands in the Hyrcanian forests of Iran. At two sites, salvage logging was applied (SL1 and SL2), and low-intensity selection cutting (SC1 and SC2) was applied at the other two. A systematic plot sampling design was used on the study area for damage assessment.
 Results: The percentage of regenerating trees damaged was 2.8, 2.1, 4.3, 1.4 %, in SL1, SL2, SC1, and SC2, respectively. The corresponding percentage of damaged trees was 4.3, 3.7, 4.9, 1.7 %. Most of the damage (48–79%) to the stand occurred during the winching stage at all the sites. Most of the wounds were located on the bole (51–78%). The average wound height and wound size at selection cutting sites were significantly higher than at the salvage logging sites. The incidence of high-intensity wounds at the salvage logging sites (55% at SL1 and 57% at SL2) was higher than at the selection cutting sites (24% in SC1 and 30% in SC2). Regenerating beech (Fagus orienalis Lipsky) and alder (Alnus subcordata C.A.Mey) had the highest incidence of damage. The number of damaged trees increased with increasing winching distance.
 Conclusion: Damage levels in stands during salvage logging and low-intensity selection cutting are lower (about a quarter) than the damage level to residual trees (12–23%) and regeneration (5–11%) from conventional selection cutting in uneven-aged mixed hardwood stands in the Hyrcanian forests. Because of the ecological and conservation value of deadwood, if the incidence of wind-fallen trees is low, the wood should be left in forest stands due to the high cost of salvage logging and the damage caused to residual and regenerating trees.
Highlights
Forest managers are concerned about the potential damage to residual trees from cyclic harvest re-entries into the same stand in forests managed under a selection cutting system (Picchio et al 2012; Tavankar et al 2015a)
Damage levels in stands during salvage logging and low-intensity selection cutting are lower than the damage level to residual trees (12–23%) and regeneration (5–11%) from conventional selection cutting in unevenaged mixed hardwood stands in the Hyrcanian forests
Deep wounds were most abundant at the salvage logging sites and shallow wounds were most common at the selection felling sites
Summary
Forest managers are concerned about the potential damage to residual trees from cyclic harvest re-entries into the same stand in forests managed under a selection cutting system (Picchio et al 2012; Tavankar et al 2015a). The damage caused to residual trees could endanger the goal of single-tree selection cutting because of a decrease in growth, increased incidence of decaying wood, and higher probability of mortality for severely damaged trees (Tavankar et al 2017a). Quality loss and fungi attack risk depend on wound intensity, tree size and species (Tavankar et al 2015b, 2017c). Wounds on nonresinous tree species, such as true firs (Abies spp.), generally result in more decay than do wounds on resinous species, such as pines (Pinus spp.). The aims of the study were to evaluate and compare stand (tree and regeneration) damage level, wound characteristics, and damage types occurring when using a cable skidder in salvage logging and selection cutting
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