Harvester-Induced Damage to Residual Broadleaved Trees Dataset

The study was carried out in six locations across France, Germany, Hungary, Lithuania, and Poland (fig. 1). A total of 288 experimental plots were established, with 48 plots per location, each of 125 m2. The selection of stands was based on a cluster analysis, an unsupervised classification method used to group forest stands with relatively homogeneous broadleaved species composition, which were found economically important and common in lowland areas of Western and Central-Eastern Europe (Erler 2007). Therefore, four dominant species were considered in the study: beech (Fagus sylvatica L.), birch (Betula L.), oak (Quercus L.), and aspen (Populus tremula L.). Characteristics of the stands, such as diameters, heights, and bark, are presented in table 1. The species were divided into two groups depending on the bark thickness: thin-barked, consisting only of beech, and thick-barked, including the remaining species: oak, birch, and aspen. The data was collected from January to March, under snow-free conditions before the onset of the growing season. To maintain similar temperature and weather conditions (Table 3), excluding the impact of harvesting season on further results, fieldwork began at the westernmost location in Allondans, France (E:6°45'29''), and ended in Kėdainiai, Lithuania (E:23°49'12"). No other conditions that could have affected the harvesting process have been observed, only brief minor snow and rainfall in Allondans and Ider Oberstein, Germany. The experimental plots were accessed by 4.0 m-wide parallel strip roads with linear layout and axes spaced 20.0 m apart. Meanwhile, all thinning was done by one HSM 405H harvester equipped with a head dedicated to broadleaved species (CTL 40 HW). There were two machine operators with different experience (Operator A – 10 000 moto hours, Operator B – 3 600 moto hours) taking part in this study. After harvesting all injuries on the remaining trees positioned on the trunk and roots with the surface area above 10 cm2 was measured, while smaller ones were considered insignificant (Meng 1977). The surface of damage was calculated using the equation of an ellipse based on the length and width of the wound. Length measurements up to 2.5 m of tree height were performed using a measuring tape, while injuries above that height were measured using an ultrasonic hypsometer Vertex. Wound widths were calculated by determining their percentage share of the trunk’s diameter, while assuming a taper of 1 cm m-1. Subsequently, injuries were classified into two groups depending on their depth: phloem or xylem damage. Moreover, depending on the distance of the occurring damages on remaining trees from the strip roads, damages were also classified into four zones: (A) 0÷2.0 m, (B) 2÷4.0 m, (C) 4÷6.0 m, and (D) 6÷8.0 m. The distance was established by an ultrasonic rangefinder Vertex.