oldgrowth

Oldgrowth refers to forest stands that have developed over long timescales with limited modern disturbance, resulting in a distinctive set of structural and compositional attributes that set them apart from younger or managed stands. The term is regionally defined and age thresholds vary, but it generally describes forests that demonstrate advanced development, with complex structure and mature or veteran trees.

Key characteristics include uneven, multi-layered canopy structure; large-diameter live trees; standing dead trees (snags) and a substantial amount of fallen logs and other coarse woody debris; extensive root systems and buttressed trunks; and a high diversity of microhabitats. These features support a wide range of organisms, from fungi and lichens to woodpeckers and other cavity-nesting species, mosses, and insects. The slow growth and long-lived nature of the trees contribute to high ecological legacies, such as long-standing seed sources and habitat continuity.

Ecologically, oldgrowth forests provide important functions. They store significant carbon, influence nutrient cycling, and help regulate water and soil processes. Disturbance events—whether windthrow, fire, or insect outbreaks—often maintain or recreate oldgrowth structure by creating gaps and maintaining diversity in age and size classes.

Oldgrowth occurs in various ecosystems, including temperate and boreal forests, some tropical montane forests, and European woodlands. Conservation and management aims focus on preserving existing oldgrowth attributes, protecting them from intensive logging or fragmentation, and, where possible, restoring wind, fire, and decay processes to sustain natural structural complexity.