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.

中文翻译：

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道格拉斯冷杉地区的可变保留期收获

从野生生物栖息地和其他重要森林功能的角度来看，西北太平洋的道格拉斯冷杉地区的可变保留收获逐渐演变，这是由于人们对对砍伐森林的生态后果的不满情绪日益增加所致。这是一种收割技术，可以保留和保留大型和古老的活树，断枝和原木等结构。可变保留是基于生物遗产的自然模型，这些自然遗产通常会在自然干扰（例如野火，风和洪水）后遗留下来。可变保留也是实现生态林业的第一个造林原则的重要技术，即在森林世代之间提供结构，功能和组成的连续性。