Notable plant rarities of northern New York alvar landscapes

Alvar landscapes occur in the glaciated region of New York where horizontally bedded limestones are covered by little or no soil. Major sites are found along the eastern end of Lake Ontario northwest of Watertown and underlain by the Black River Group limestones. They are naturally open landscapes with scant tree cover often restricted to bedrock crevices. New York alvars are home to state-rare elements, including seven natural plant communities and 57 rare plant species. Floristic assemblages are diverse and include several disjunct species with northern, southern and midwestern (prairie) affinities. The mosaic of distinctive plant communities is adapted to extreme environmental conditions including seasonal fluctuation in moisture and temperature, variable shallow soil depths, localized runoff patterns, and cryopedogenic processes. They are also subject to recurring human disturbances such as fuelwood and fence post cutting, accidental fires, and introduction of drought tolerant nonnative species. Combined, these factors support a surprisingly high biodiversity in alvar landscapes.