Figure 1. Presettlement forest types of Ohio (based on Gordon, 1966).
For a resource manager interested in restoring plant communities in disturbed ecosystems, the identification of reference vegetation conditions is an important step in the process of forest ecosystem restoration (Aronson et al., 1995; Pickett and Parker, 1994). Identifying reference conditions (e.g., composition, structure, and function of woody and herbaceous species) for a specific ecosystem, however, is often a very contentious issue.
Successional pathways and plant community composition and structure can be highly variable, making it difficult to use historical plant communities as templates for restoration (Wyant et al., 1995). This is particularly true for riparian areas, where variation in physiography, disturbance regimes, and soil characteristics can result in a diverse array of plant communities at a variety of spatial scales (e.g., Gregory et al., 1991; Bendix and Hupp, 2000).
A common source of information on historical plant communities that has often been used to identify reference conditions for forest ecosystem restoration is the original surveyor notes of witness trees, such as those developed by the General Land Office (GLO) in the early 1800s. From these surveyors' notes, the pre-European settlement distribution of forest ecosystem types has been developed, and relatively detailed information on the historical composition and structure of these forests has been determined.
For example, in Ohio, Gordon (1966) developed a pre-European settlement map of forest types, and many resource managers and conservation organizations use this classification to guide their selection of reference vegetation conditions (Figure 1).
Other less utilized sources of information on reference vegetation conditions for forest ecosystem restoration are the remaining relatively undisturbed old-growth forest ecosystems. Although less than 1% of the pre-European settlement forests remain in Ohio (Davis, 1996), there are examples of minimally disturbed old-growth (> 150 years old) and mature second-growth (120 to 150 years old) forest ecosystems in Ohio, many of which are located on public lands (e.g., Goebel and Hix, 1996).
Although they often represent a small area, these forests provide an opportunity to study vegetation-environment relationships and develop predictive models of forest ecosystem development that can be used to develop templates for the restoration of forest composition and structure. As many of these old-growth forest ecosystems also have small streams and rivers flowing through them, they may provide useful information to develop reference conditions for riparian forests.
The objective of our report is to review the relevant literature related to the pre-European settlement forest-type surveys and the few remaining old-growth forest ecosystems in each of Ohio's ecoregions (McNab and Avers 1994; Figure 2) to: