Damage to residual trees following commercial thinning by harvester and forwarder in a Pinus taeda stand in Southern Brazil

Abstract

This study assessed the damage to residual trees in forest stands thinned by both a wheeled harvester and a forwarder. Data collection took place at a company located in the State of Paran, in Southern Brazil; in 12-year-old Pinus taeda stands conducted to their first thinning; and in terrains from 0 to 10 and 10 to 20 slope classes. Damage to residual trees was assessed by intensity, location, and wound area. Damage was compared by the t-test at a 5% probability level, while wound area was analyzed by minimum, mean and maximum values. Results showed high total damage percentages after the harvesting, with 36.1% and 29.1% in the 0 to 10 and 10 to 20 slopes, respectively, but without statistical difference. Most of the damage was caused by the movement of the harvester boom while cutting trees during the selective thinning process. Moreover, most of the damage appeared on the trunks of 11.6% residual trees, on the sides facing the road and the stand, with an mean wound area under 100 cm. The wheeled harvester is not recommended for the first thinning in planted forests, because of the high damage to residual trees.