Natural Communities of NH -- Photo Guide

Vernal floodplain pool


NOTE: This community has been deleted. Vernal pools are considered important ecological features, but not distinct natural community types.

Vernal pools are small, isolated depressions that are generally flooded only seasonally and often dry out completely during the course of the growing season. Water levels are controlled by precipitation and groundwater fluctuations. The cycle of wet and dry phases prevents the establishment of fish populations. With these predators excluded, vernal pools are safe harbors for numerous animal species, and serve as important feeding and breeding grounds for reptiles, amphibians, and invertebrates, several of which are adapted to and completely dependent upon the cyclic and ephemeral nature of these wetland basins.

Vernal pools typically are not large enough to break the forest canopy above. They range from unvegetated to sparsely or sometimes moderately vegetated. They are defined biologically by characteristic animal species, not vegetation. Plant species richness and cover are highly variable and typically low. Vegetation is often restricted to elevated mounds or areas near the pool margins.

Two natural community types are described (vernal woodland pool and vernal floodplain pool). Vernal floodplain pools are less common and are occasionally inundated by floodwaters. They differ from oxbow marshes in that they lack the robust marsh vegetation of those floodplain communities. Larger isolated vernal basins with perennial or annual vegetation are alternatively referred to as basin marshes, although functionally they are also vernal pools.

Vernal floodplain pool near the Merrimack River in Concord (photo by Ben Kimball for the NH Natural Heritage Bureau)
vernal floodplain pool near the Merrimack River in Concord (photo by Ben Kimball)

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