Vernal pool
[2] Most pools are dry for at least part of the year, and fill with the winter rains, spring snowmelts and rising water tables.
[3] Some authorities restrict the definition of vernal pools to exclude seasonal wetlands that have defined inlet and outlet channels.
The justification is that such seasonal wetlands tend to be qualitatively different from isolated vernal pools; this is because they are fed by larger drainage basins so that firstly, inflow contributes higher concentrations of dissolved minerals.
Low dissolved mineral concentrations of smaller vernal pool basins may be characterized as oligotrophic, and poorly buffered with rapid pH shifts due to carbon dioxide uptake during photosynthesis.
While many vernal pools are only a few meters in width, playas and prairie potholes are usually much larger, but still are otherwise similar in many respects, with high water in wet periods, followed by dry conditions.
[5] Some exclude desert playas from the definition of vernal pools because their larger closed drainage basins in areas with high evaporation rates produce higher concentrations of dissolved minerals, with salinity and alkalinity favoring different species.
[6] Despite being dry at times, vernal pools teem with life when filled, serving as critical breeding grounds for many amphibian and invertebrate species.
[8] Vernal pools harbor a distinct assemblage of flora and fauna that, in some cases, aren't found anywhere else on the planet.
Disturbingly, much of this destruction has occurred in recent years, with about 13% of remaining vernal pools being lost in the short interval from 1995–2005.
[citation needed] Vernal pools are prime habitats to be targeted for restoration work due to their value as hotspots of biodiversity as well as recent history of extensive destruction and degradation.
Several hypotheses have attempted to explain this: Results: Research suggest that the last two details (Hypothesis 2 & 3) are crucial in determining the habitat value of man-made vernal pools.
There has been a fair amount of controversy surrounding the practice of mitigation, which is the destruction of protected or endangered species and habitats, such as vernal pools, on the condition that whatever entity (business, land manager, etc.)
Thus, it has been very controversial to apply mitigation strategies to vernal pool systems due to the obvious risks inherent in trying to reconstruct this kind of habitat.
Some agencies, however, are now requiring two replacements for every vernal pool that is destroyed to compensate for the lower quality of human-made habitat.
In many instances they contain grasslands that form over a variety of soil types containing silts and clays often covered by a layer of interwoven fibrous roots and dead leaves.
Soils in vernal pools often reflect their inundated conditions, leading to low chroma horizons, mottling, and anoxic decay.
Most pools receive annual deposition of tree leaves, which are critical to maintaining local life due to leaf detritus.
Listed below are some genera of the approximately one hundred vascular plant species associated with California vernal pool habitats.
In California and New York state, the endangered tiger salamander (Ambystoma tigrinum) is dependent on vernal pools to breed as described above.
[citation needed] Some other species, notably Anostraca, fairy shrimp, and their relatives, lay eggs capable of entering a state of cryptobiosis.
As an extreme example, Branchipodopsis relictus on the main island of the Socotra archipelago, which is exceedingly remote for what it is, a continental fragment of Gondwana, is believed to have been isolated since the Miocene.
