Can Understory Plant Composition and Richness Help Designate Riparian Management Zones in Mesic Headwater Forests of the Northeastern United States?

Riparian buffers implemented to minimize sediment, nutrients, and disturbance impacts on streams during forest operations vary greatly in the degree to which ecological criteria are used in their design. Because most forest operations are concentrated around headwater streams, our primary research objective was to identify a floristically based riparian boundary for headwater streams using plant species composition and indicator species to classify riparian environments distinct from the surrounding upland forest. Within three forested regions of the Northeast US, understory vegetation plots were sampled along perpendicular transects extending from the stream bank into the upland forest. At all sites, species richness was highest adjacent to the stream, decreasing exponentially within 6-12 m from the channel. Species composition closest to the stream was significantly different from all other lateral distances, but identified riparian indicator species were of limited practical use across all sites. However, changes in species richness can serve to identify a riparian area extent up to 6-12 m from headwater streams.