Old Growth Characteristics

Forest Trees of Great Age - Great age may be defined as trees exceeding 50% of the projected maximum attainable age for a particular species. The quality of the site may greatly affect the size of the trees.

Uneven-Aged Canopy Structure - Especially true in the eastern U.S., the varying ages and diameters of trees in old-growth forests are largely the result of small-scale natural disturbances and differential shade tolerance among species.

Downed Logs - Downed logs are a prominent component of the forest floor. These logs, varying in size, contain much of the nutrients present in a tree stand. They are important in maintaining forest hydrology and function as important wildlife habitat.

Standing Snags - Standing dead wood is important for a variety of wildlife species.

Treefall Gaps - Gaps are a common occurrence in old-growth, resulting from many small wind-caused blowdowns of one to several trees. Due to treefall gaps, greater sunlight reaches the forest floor resulting in 3-5 tree age layers rather than 1-2 layers found in younger forests.

Pit and Mound Topography - Old-growth soil surfaces are often dominated by the pit and mound rolling topography. The “pit and mound” structure is a result of root mat and associated soil of windthrown trees ripped up from the forest floor, forming a depression or pit. The later decaying root ball and loosening soil fall into a mound. This topography is important in forest nutrient cycling and in understory diversity.

Undisturbed Soils - Old-growth forests typically have soils that are high in organic matter and are not compacted. The thick layer supports a considerable number of ferns, mosses, and fungi.

Ecosystem Stability - Most old-growth forests approximate a dynamic steady-state condition where they ebb and flow around a mean. For example, mortality generally balances growth and nutrient input is roughly equivalent to nutrient output.

Diversity of Plants and Animals - Certain species of salamander, soil invertebrates, small mammals, songbirds, black bear, and others are often found in greater abundance.