Seral Classification
Every year in B.C. forests are subjected to various disturbances including human activity (e.g., logging, land clearing, grazing), and natural agents (e.g., wildfire, wind, insects, disease). Disturbance changes the plant community, but, given enough time, the original plant community may recover. This process of change after disturbance is called succession and the different plant communities that occur during this process are seral stages.
The seral (often termed successional) classification in BEC is an integration of site and vegetation classifications with structural stage development. However, seral plant communities are poorly described in B.C due to a lack of sampling. Seral plant communities are highly variable, making successional pathways difficult to predict. Complex interactions among many factors, including disturbance type, severity, and frequency, vegetation present before disturbance, seed and bud banks on a site and sources of seeds in the vicinity, and weather following disturbance, all influence plant community development. Adding the factor of time into the equation greatly increases the number of plant communities that need to be described to develop an adequate seral classification.
Within the BEC system, seral plant communities are grouped into plant associations, just as mature communities, and may occur in several different variants or span several stages during succession. The concept of structural stages (Hamilton 1988; DEIF 1998) is used within the BEC system, as a framework for describing seral plant associations. This scheme uses seven stages, some of which are further divided to accommodate specific situations. See Chapter 1 (Site) in DEIF for detailed definitions of structural stages.
One site association can include a variety of disturbance-induced, or seral, ecosystems, but succession should ultimately result in similar plant communities at climax throughout the association. The use of plants from the climax plant association to name site associations does not mean that climax vegetation dominates the present landscape. Many ecosystems in the province reflect some form of disturbance and are in various stages of succession towards maturity. Site associations can be differentiated from one another by a range of environmental properties. These site properties are used to identify a site association in an early successional stage.
Seral units provide the "chronological" level of ecological integration.