Pteridophyte assemblage composition and richness as a reflection of woodland maturity in an eastern riparian zone

Zoar Valley Gorge in western New York State contains an ecologically significant remnant of old growth riparian forest totaling as much as 300 ha. Forested riverside terraces (former floodplains) also harbor a diverse herbaceous flora including numerous species of ferns and fern allies (Pteridophyta). Due to geographic isolation, these terraces have experienced very little human interference. During 2003 – 2005, the pteridophyte flora was systematically surveyed on nine riverside terraces representing a chronosequence of core-based canopy age from 109 – 351 years. A number of taxa that may indicate high ecological integrity (e.g., Diplazium pycnocarpon and Dryopteris goldiana) were found to be conspicuously abundant. Floristic surveys suggest a connection between overstory stand age and fern assemblage composition. The least mature terrace harbored only three fern species while older terraces, or terraces of variable stand age, were more diverse with up to 13 pteridophyte species. Ongoing quadrat and transect sampling is quantifying fern colony density and abundance, including alpha, beta, and gamma species diversity, and will further explore the possible association of pteridphyte community structure with forest maturity.