Evenaged

Evenaged describes a forest stand in which most trees are of a similar age, typically resulting from a regeneration event that eliminates most individuals of other ages, such as a stand-replacing disturbance or the planting or seeding of a site. In an evenaged stand, the age range is narrow and the diameter distribution tends to be uniform, reflecting a cohort that established at roughly the same time.

Causes and regeneration methods often include clear-cutting, shelterwood, or seed-tree systems that establish a uniform age class. Regeneration may be natural, through seed fall and germination after disturbance, or artificial, through planting or direct seeding. Rotation lengths and species choices depend on site quality, climate, and commercial objectives, and can range from a few decades to many decades for slower-growing species.

Management implications center on predictable yield and simpler harvest scheduling. Uniform age structure allows coordinated thinning and harvest events, but can increase vulnerability to pests, diseases, or climate events that affect the entire cohort. Silvicultural practices may aim to maintain or adjust the stand through thinning, spacing, or occasional retention of structural features to preserve biodiversity and reduce risk.

Ecological characteristics include rapid early growth in young stands, followed by canopy closure and self-thinning as trees compete for resources. Even-aged stands often have relatively low vertical and species diversity in their mid-life stages, though management can introduce complexity through selective thinning or understorey management.

Compared with uneven-aged forests, evenaged systems emphasize uniform structure and predictable production, while uneven-aged systems emphasize continuous cover and greater structural diversity.