Figure 2. Ecoregions of Ohio (McNab and Avers, 1994) and location of remaining old-growth and mature second-growth forests with information on riparian forests published in a refereed journal article.
Riparian areas are functional ecotones or transitional areas located between terrestrial and riverine ecosystems. Despite their limited areal extent, riparian areas promote many ecosystem functions vital to the health and productivity of forested watersheds. Not only do riparian areas regulate the flow of water, sediments, and nutrients across system boundaries, they also contribute organic matter to the aquatic system, increase bank stability, reduce erosion, and provide key wildlife habitat (Gregory et al., 1991; Ilhardt et al., 2000).
Additionally, because of their functional importance, riparian areas serve important roles in mitigating many of the negative impacts of land use on aquatic systems as well as protecting species diversity, providing potential dispersal corridors for wildlife, and mitigating flood waters (Ilhardt et al., 2000; O'Laughlin and Belt, 1995). Unfortunately, we have a poor understanding of the patterns of variation in riparian areas within and among watersheds, or the specific landscape features that control riparian vegetation development.
Increasingly, riparian areas across Ohio are experiencing pressure from a variety of sources, including developers, farmers, and recreationists. Detailed assessments of relatively undisturbed riparian areas are critical elements needed for a variety of ecological purposes, especially for providing a benchmark of reference ecological conditions necessary for evaluating forest ecosystem restoration programs.
Voluntary best management practices (BMPs) promoted by various state agencies (e.g., the Ohio Department of Natural Resources, ODNR) may be available and utilized in riparian areas (Blinn and Kilgore, 2001). However, the effectiveness of these practices to help restore or even maintain critical ecosystem linkages is untested. These practices are certainly not site-specific in their application (e.g., the width of riparian management zones is often fixed arbitrarily rather than being based on a functional delineation of riparian extent; deMaynadier and Hunter, 1995).
One important consequence of a shift toward a functional definition and delineation of riparian areas is the need for an explicit quantification of reference, or benchmark, riparian conditions (Gregory, 1999). Although current management systems incorporate the best available science, our understanding of specific riparian areas and the extent of the functions associated with these land-water interfaces is often incomplete (Blinn and Kilgore, 2001).
Understanding the range of variability in these reference riparian areas is important as they represent the goal of riparian restoration and management efforts (i.e., the undisturbed riparian area with all ecosystem linkages intact) and provide a metric or standard with which to compare current and future riparian restoration and management programs.
While we know very little about the composition and structure of the riparian forests in the state, many of the current restoration and management systems used in riparian areas in Ohio, as well as other areas in North America, are based on extending our understanding of forest stand dynamics from upland forests or other riparian settings in different regions (Blinn and Kilgore, 2001; Gregory, 1999). The simple fact that there is a diverse array of environmental gradients distributed across riparian areas (e.g., microclimate, flooding) not found in upland settings, or other riparian systems, suggests that these comparisons may not be valid (Gregory, 1999).