Abstract

Vernal pools are small, shallow wetlands that usually dry annually. They often are inundated by snowmelt and spring rains and are frequently dry by the end of summer, although some pools do not become dry every year. These wetlands occur globally and are widespread in North America along the Pacific Coast, in the glaciated Northeast and Midwest and in parts of the Southeast. The hydroperiod (days with surface inundation) and hydroregime (timing of inundation) are the primary factors determining the flora and fauna occupying these pools. The geomorphological setting of vernal pools is variable, with pools along the Pacific Coast perched above impervious substrates, while pools occur across a broader spectrum of geological settings in the eastern North America. Biologists are just beginning to understand the complex food webs and life histories of the flora and fauna of these biodiversity hotspots. In some parts of the world, vernal pools are well known for their flora, invertebrates, and vertebrates. Due to habitat loss and other anthropogenic impacts, several endangered species occur in vernal pools, thus this habitat type is a major conservation concern for biologists.