What is Old Growth?

Authored By: H. M. Rauscher

The essence of the old growth concept refers to forests that are relatively old and relatively undisturbed (Tyrell and others 1998). Although quite a few definitions for old-growth forests have been developed for eastern forests, no wide-spread concensus has been achieved. Why? Because definitions matter in practice. "Old growth" is as much, if not more, a political concept as it is a scientific concept. How old growth is defined may lead directly to decisions about which forest areas can be commercially harvested and which cannot. For example, strict definitions of old growth result in smaller acreages off-limits to commercial logging (Leverett 1996). Conversely, loose definitions may result in larger acreages off-limits to commercial logging.

Most people have an intuitive, common-sense-based concept of old growth. But it varies depending on personal experiences, cultural background, and educational exposure. Tyrell and others (1998) argue that despite these differences, people do agree on some core characteristics of what old growth is or should be:

"Old, uneven-aged forests, with large trees and lots of dead wood, located on productive sites at low elevations that have not experienced large-scale natural or human disturbance, embody the quintessential old-growth concept" (Tyrell and others 1998).

As one moves away from this core concept of old growth, consensus rapidly disappears due to inherent problems defining old growth. Yet there exists a need for just such a consensus to allow inventorying stands and rating the degree to which they contain old-growth characteristics, prioritizing forests for protection and allocation to the old-growth category, and determining whether and when non-old-growth forests can acquire old-growth status.

Despite this lack of consensus, old-growth definitions still exist (Tyrell and others 1998). There are both conceptual and practical ways to define old-growth. Conceptual definitions create a theoretical framework from which operational definitions and models can be derived. Operational definitions provide clear identification criteria which allow for the classification of individual forest stands as either old growth or not or, more usefully perhaps, provide a metric which estimates the degree of old-growthness a particular stand embodies.

Old growth definitions for several forest types in the southern Appalachians have been synthesized from years of research. Examples of these definitions are available for the follow forest types: