Disturbance Scale

A common way to classify disturbance events is based on the extent of the area with direct impacts. The spatial scale of the disturbed area is closely tied to the magnitude of the disturbance and the specific disturbance mechanism. For example, large-scale disturbance events are those that impact a large spatial area and thus have a relatively high magnitude on the local ecosystem. Using these criteria, disturbance events can be divided into three classes. Beginning with the largest category, these are stand replacement-scale, incomplete stand-scale, and gap-scale disturbances. A relationship exists between disturbance scale and disturbance return interval (Lorimer 1989). Gap-scale disturbances are most common in mature stands. If a forest is characterized by a relatively high frequency of large-scale disturbance events, stands may never reach the stage of development when gap-scale disturbances are common.