Variable retention harvesting in the Douglas-fir region

Variable retention harvesting evolved in the Douglas-fir region of the Pacific Northwest gradually in response to increasing dissatisfaction with the ecological consequences of clear-cutting, from the standpoint of wildlife habitat and other important forest functions. It is a harvesting technique that can provide for retention (continuity) of such structures as large and old live trees, snags, and logs. Variable retention is based on the natural model of the biological legacies that are typically left behind following natural disturbances, such as wildfire, wind, and flood. Variable retention is also an important technique for fulfilling the first silvicultural principle of ecological forestry, that of providing for continuity in structure, function, and composition between forest generations. The history and current application of variable retention approaches on forests in western Washington and Oregon states (USA), where many of the fundamental concepts were first developed and applied, is described in this article.