Abstract
The aim of this study was to investigate the effect of season of the year on the frequency and degree of damage to residual trees caused during winter and summer timber harvesting operations in young alder stands. Analyses were conducted in pure black alder (Alnus glutinosa Gaertn.) stands aged 38 and 40 years, located in north-eastern Poland. Chainsaw logging was performed in the cut-to-length (CTL) system, while timber was extracted using an agricultural tractor with a trailer with manual timber loading and unloading. Damage caused in the stand as a result of early thinning operations was evaluated in terms of: (1) damage location, (2) wound size, (3) wound depth, and (4) the distance of the damaged tree from the skid trail. Timber harvesting caused damage in 8.3% of trees remaining in the stand. Both the total number of damaged trees (p = 0.001) and the number of trees damaged during felling (p = 0.01) and extraction of timber (p < 0.001) were greater in summer than in winter. Irrespective of the season, two-thirds of all cases of damage were caused during timber extraction, with 67.7% of damage recorded on trunks or root collars and 32.3% on roots. Irrespective of the season and the technological operation, slightly over 50% of cases of damage were small wounds of max. 10 cm2. The proportions of medium-sized wounds (11–100 cm2) and large wounds (over 100 cm2) were comparable. The majority of damaged trees (85.1%) were found in the vicinity (<1 m) of the skid trails. The frequency of tree damage near the skid trail was twice as large in summer as in winter (p < 0.001).
Highlights
Timber harvesting causes enormous disruption to the natural environment
Irrespective of the season, two-thirds of all cases of damage were caused during timber extraction, with 67.7% of damage recorded on trunks or root collars and 32.3% on roots
Upon completion of the early thinning operation in the 24 experimental plots a total of 4718 trees were left in the stands, with an average of 196 per plot. 390 trees were damaged, which accounted for
Summary
Timber harvesting causes enormous disruption to the natural environment. Apart from tree damage, it leads to degradation of the undergrowth, ground layer and soil [1,2,3,4,5,6,7,8,9]. In view of the increasing ecological and economic importance of damage occurring in stands during timber harvesting, many researchers have investigated the potential to reduce such damage [10,11,12]. Meyer et al [13] reported the adverse effect of various machines used in timber cutting on the forest environment (the stand, undergrowth and soil). Studies concerning such damage have focused primarily on pine stands [7,10,14,15]. There are no publications presenting the results of similar investigations conducted in alder stands
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