Amount and Location of Damage to Residual Trees from Cut-to-Length Thinning Operations in a Young Redwood Forest in Northern California

A cut-to-length (CTL) harvest system using a harvester and forwarder has been recently introduced in northern California (USA) for thinning young (<25 years old) redwood forests (Sequoia sempervirens (Lamb. ex D. Don) Endl.). However, the severity of CTL damage to residual trees in this forest type are unknown. The goals of this study were to (1) determine the location, size, and number of scars resulting from CTL harvesting and (2) compare scar size differences between redwood clumps and individual trees in two units. Most scars occurred on trees located near the forwarding trails. Wider and longer scars were associated with clumped trees (9.1–12.2 cm wide and 28.1–46.2 cm long) as compared to scars on individual trees (8.1–9.5 cm wide and 16.7–31.3 cm long), and 16–32% of the residual trees were scarred. Determining a minimum scar size will define the severity of stand damage; larger scars result in a longer time until closure. However, counting all the smaller scars that result from CTL harvesting will result in a large number of counted damaged trees. Therefore, we suggest that scars smaller than 5–10 cm width are acceptable on coastal redwood after CTL thinning.