What makes an old-growth forest recognizable?
Old-growth forests are usually composed of trees of different sizes and ages, and thus have several canopy layers. Particular forest types have openings in the canopy of a characteristic size and distribution pattern. Another feature of old-growth forests is high biomass accumulation compared with younger stands of the same forest type. Biomass may be present in various quantities, as live or dead standing trees, fallen trees, or woody debris in various stages of decay. Some old-growth forests may have considerable biological diversity, fostered by the variety of tree ages and sizes of canopy openings. These stand structures may provide habitat for specialized wildlife. For example, certain moss, lichen, fungi, and insect species tend to be more numerous in old-growth forests than in younger stands of the same forest type. In particular, vertebrates, invertebrates, plants, fungi, and bacteria associated with dead wood are abundant in old-growth forests.
