What kind of forest is characterized as old growth?

Old growth forests are defined as those that have developed over a long period of time without significant disturbance from human activities. These forests typically exhibit a diverse range of tree ages, sizes, and species, and they often host complex ecosystems. The lack of disturbance allows for the natural processes of forest aging, which can result in large, mature trees with unique features such as wildlife habitats, diverse understory plants, and rich soil profiles.

In contrast, forests planted by humans are generally managed for specific outcomes and don't typically contain the age structure, biodiversity, or ecological characteristics associated with old growth forests. Forests made up primarily of pine trees may not necessarily be old growth if they do not meet the criteria of age and undisturbed conditions. Additionally, forests at high altitudes can vary greatly in their characteristics and do not exclusively define what an old growth forest is, as old growth can be found in diverse elevations and climates. Thus, the defining aspect of old growth forests is their undisturbed nature over centuries, allowing them to mature and develop rich ecosystems.