Effects of Varying Levels and Patterns of Green-Tree Retention on Amount of Harvesting Damage

An inventory of fresh logging wounds from treatment implementation was performed in a regional green-tree retention experiment in Oregon and Washington. The DEMO (Demonstration of Ecosystem Management Options) study contains six treatments replicated in six blocks: (1) 100% retention (control), (2) 75% aggregated retention, (3) 40% dispersed retention, (4) 40% aggregated retention, (5) 15% dispersed retention, and (6) 15% aggregated retention. Over all blocks and treatments, Douglas-fir (Pseudotsuga menziesii) and western hemlock (Tsuga heterophylla) comprised 74.9% of all measured trees, and the proportion of trees damaged was similar for both species. Suppressed trees tended to be more susceptible to damage than were trees in other crown classes. A greater proportion of trees in the dispersed retention treatments were damaged than in the aggregated treatments. Only in the two dispersed retention treatments were levels of damage significantly different from the control (P 25 cm dbh) trees. Some evidence was also found that the sites with gentler slopes had less damage than those with steeper topography. Probable effects of wounds on future growth and tree health could not be inferred as no data were collected on wound size or height. However, it is expected that the future incidence of stem rot and growth reduction will be greatest in the dispersed retention treatments. West. J. Appl. For. 17(4):202–206.