Even-aged timber management

Even-aged timber management is a group of forest management practices employed to achieve a nearly coeval cohort group of forest trees. The practice of even-aged management is often pursued to minimize costs to loggers. In some cases, the practices of even aged timber management are frequently implicated in biodiversity loss and other ecological damage. Even-aged timber management can also be beneficial to restoring natural native species succession. The first step in even aged timber management is to select a suitable stand for harvest. Trees must be of merchantable size, a desirable species, and in an area accessible to harvesting equipment. Once selected, the stand is harvested (usually using feller-bunchers, skidders, and processors). Merchantable trees (trees with boles large enough to be sold to a mill) are harvested and processed whereas unmerchantable trees (trees that are too small or of an undesirable species) are either crushed by machinery or cut to make equipment movement easier. This process is called clearcutting, and the result is a cutblock. At this stage, the forestry company is required to replant the same proportion of species that were there previous to harvest. Usually, silviculture techniques are employed to ensure that species survive and grow in the proper proportion. Shade-intolerant species such as trembling aspen (Populus tremuloides) and marsh reedgrass (Calamagrostis canadensis) will thrive in the open conditions of a clearcut, outcompeting shade-tolerant species such as white spruce (Picea glauca). Mechanical site preparation and herbicide treatments are often applied initially to allow for adequate shade-tolerant growth. This way, the shade-tolerants are given a head start and the shade-intolerants will catch up over time once silviculture treatments are stopped, resulting in an even-aged stand of trees with little vertical stratification. Even-aged forest management is the harvesting system of choice in many parts of the world because it is often considered to be the only method that is economically viable.