Nearctic Vernal Pools and Ephemeral Wetlands - Code: Ne11E

Vernal Pools and Ephemeral Wetlands form in small depressions following prolonged periods of precipitation. Pools are filled by melting snow, runoff or rising ground water. Frequently pools are found over areas with near surface bedrock or hardpan clay that prevent drainage. In the western US this usually occurs in late winter and early spring (December to March) while in the east Vernal Pools are most active between February and May. Vernal Pools and Ephemeral Wetlands are not connected to permanent water sources and undergo complete drying for long periods. 
Eastern Vernal Pools do not have a distinctive array of plants and often exist in periods with little or no plant growth occurring. Vernal pools often occur as at wetland element within eastern temperate forests including Nearctic Temperate Deciduous Forest, Nearctic Temperate Mixed Forest, Cypress Tupelo Gum Swamps, Bottomland Hardwood Forest and Eastern Pine Savanna. Red Maple (Acer rubra), Silver Maple (Acer saccharinum), American Beech (Fagus grandifolia) and Black Tupelo (Nyssa sylvatica) are trees commonly found around vernal pools. Common plants found around vernal pools in the east include buttercups (Ranunculus sp.), sedges (Carex sp.), pondweed (Potamogaton sp.), skunk cabbage (Symplocarpus foetidus) and various ferns.
In the western United States, vernal pools are often found within Pacific Chaparral, California Oak Savanna and anthropogenic grazing lands. Due the relative scarcity of water in these habitats, vernal pools in the western United States do have a more unique herbaceous plant community. Over 100 species of plants are endemic to vernal pool systems in California, many of these threatened or endangered. Calicoflowers (Downingia) are a group showing a particular affinity for vernal pools and a high degree of endemism.