Dr. Susan Kalisz,
University of Pittsburgh Department of Biological Sciences

The conservation and restoration of river systems is an area of global concern and action (Dynesius and Nilsson 1994). Riparian zones, the areas of contact between land and water along streams, rivers, ponds, lakes, and wetlands and the plants that live in them are key components in river ecosystem stability (Wetzel, 2001 Chapter 10). Riparian plants' root systems help to stabilize riverbanks and stream banks, reduce erosion and decrease runoff and therefore significantly decrease the concentration of diverse nutrients, including nitrogen and phosphorus and other pollutants entering the river. Riparian plants provide habitat structure, food for terrestrial organisms and maintain water temperature through shading. Research in this area indicates the importance of riparian zones in the health and function of watershed ecosystems (reviewed in Ward and Tockner, 2001). However, long-standing disturbance of the river and riverbank creates conditions that both diminish the local native biodiversity in the plant community and can foster the invasion of non-native plant species (e.g. Gilvear et al., 2000). Both of these factors can diminish ecosystem health. Understanding the structure and composition of plant communities along rivers in the context of the management (disturbance) milieu is a key first step in maintaining and/or improving river function and health. The Botany Team's goal in 3R2N project is to create a large-scale spatially referenced database of woody vegetation and selected herbaceous plants. This database will be used to determine the occurrence of native plant communities and invasive species in the context of human management of the Three Rivers.

• The data to date from the vegetation surveys of 2000 and 2001 indicate that the riverbanks house a diverse assemblage of woody plant species.
• Four woody plant communities and one herbaceous plant community have been identified.
• Introduced species comprise 15-24% of the total woody species abundance of the riverbanks. However, a lower proportion of those are invasive.
• Tree of heaven and Japanese knotweed are the most invasive species noted to date.
• There are several areas regions of the riverbank that are worth protecting, especially the remnant floodplain forests.