VERNAL POOL

'Vernal pools', also called 'ephemeral pools', are temporary pools of water. They are devoid of fish, and thus allow the safe development of natal amphibian and insect species.

Contents

Range

Characteristics

Flora

Fauna

See also

External links

Range

A vernal pool is

"a seasonal body of standing water that typically forms in the spring from melting snow and other runoff, dries out completely in the hotter months of summer, and often refills in the autumn. Vernal pools range from broad, heavily vegetated lowland bodies to smaller, isolated upland bodies with little permanent vegetation. They are free of fish and provide important breeding habitat for many terrestrial or semiaquatic species such as frogs, salamanders, and turtles."

"Vernal Pool." The American Heritage® Science Dictionary. Houghton Mifflin Company. 03 Jun. 2007. .

Characteristics

Ephemeral snowmelt pool in the Sierra Nevada, Toulomne County, Calif.

The pools are dry most of the year and fill with the winter rains or snow melt.
They are called vernal pools because they are at their peak in the spring, ("vernal" meaning of, relating to, or occurring in the spring).
Despite being dry most of the year, once filled they are teeming with life. The most obvious inhabitants are various species of frogs and toads. Living in the water the most notable inhabitants are daphnia and fairy shrimp, which are often used as an indicator species to decisively define a vernal pool.
Further north, tadpole shrimp are also common.
One of the best studied vernal pool habitats in the world is Frog Pond in Orono, Maine.

Flora

Vernal pool flowers, with different species occurring in bands related to soil moisture and temperature gradients formed as the pool dries out. Sacramento National Wildlife Refuge, Calif.

In vernal pools, flowering occurs simultaneously because of the seasonality of favorable conditions. Vernal pools are home to many endemic species because of the unique environmental niches created by acidity and salinity gradients.
Different species are suited to different moisture levels, and as water evaporates from the edges of a pool, rings of flowers blossom around it. The color patterns change as the wet season wears on. The rings may form swirls and layers, with the green of new grass surrounding the whole pattern.
Flora commonly found at vernal pools include ''Downingia'' and lupine species, yellow pansies, several sweet-scented clovers, a variety of goldfields, button parsleys, yellow and bright lavender monkeyflowers, star lilies, yarrow, and endangered grasses such as Solano grass.
Because of their characteristics, vernal pools are often threatened by development in the same way that wetlands are.
As a result, most pools have been converted into residential zones, roads, and industrial parks. That is why most extant pools occur on protected or private land such as national parks, and ranches.
A large number of rare, endangered species, and endemic species occur in vernal pool areas. For example, the San Diego mesa mint, a highly endangered plant, is found exclusively in vernal pools in the San Diego area. Another example is the wildflower ''Lasthenia conjugens'', which is found in limited parts of the San Francisco Bay Area. A third example is the herb ''Limnanthes vinculans'' endemic to Sonoma County, California.

Fauna

Many of the amphibians that breed only in vernal pools spend most of their lives in the uplands within hundreds of feet of the vernal pool. Eggs are laid in the vernal pool, then the juveniles leave the pool two or three months later, not to return until the following spring to breed. Therefore, the upland areas surrounding a vernal pool are critical for the survival of these species.

See also

★ Ephemeral pool

★ Autochthon

★ California native plants

★ Swamp

★ Bog

★ Wetland

External links

★ Vernal Pool Association

★ California Vernal Pools

★ Jepson Prairie Reserve

★ Ontario Vernal Pool Association

★ [1]

★ [2]

★ [3]

★ [4]