Vernal Pools, A Home for Plants and Animals

Vernal pools are temporary bodies of water that provide a habitat for certain plants and animals. The pools can range in size from small puddles to shallow lakes and are considered a type of wetland. Vernal pools usually do not contain fish, which allows for the safe development of insect and amphibian species that are unable to withstand predation by fish. Vernal pools are most often at their maximum depth during the springtime, and while they can form in forests they are most often found in grasslands. The majority of vernal pools are dry for at least part of the year, making them seasonal wetlands.

Vernal pools are an important part of the ecosystem as they provide a unique habitat for many different plants and animals that would be unable to survive and thrive under other conditions. Many of the plants and animals that are found in vernal pools spend the dry season as eggs, seeds, or cysts, which are then able to grow and reproduce when the pools refill. In addition to providing a habitat for plants and animals, vernal pools are also used by birds as a seasonal source of not only water but food.

How Vernal Pools are Formed

Vernal pools form due to the seasonal cycle of flooding and drying. Most pools flood, or form, due to water from rain, melting snow, or high groundwater, in the spring. While many pools form in the spring, others will form in autumn, and will hold water all throughout the winter and spring, drying up during the summer.

Animals Found in Vernal Pools

The organisms that can be found in vernal pools fall into two different categories. The obligate vernal pool species depend completely on the pools for certain phases of their life cycles. The vernal pool habitat is required for obligate species to successfully breed and thus survive. Facultative species are those that are found in or around vernal pools but are not completely dependent on the pools for survival. Facultative species are able to use other wetland habitats for the various phases of their life cycles. Some of the obligate species found in vernal pools include Spotted Salamanders, Wood Frogs, Fairy Shrimp, Jefferson Salamanders, and Blue Spotted Salamanders. Some of the facultative species found in vernal pools include Leopard Frogs, American Toads, Spring Peepers, Red Spotted Newts, and Green Frogs. In addition to amphibians, there are many different inspect species that rely on vernal pools for survival.

Plants Found in Vernal Pools

Perennial plants are generally unable to withstand the conditions in a vernal pool and as such most of the plant species found in vernal pools are annuals. A vernal pool will typically include anywhere between fifteen and twenty five different plant species. Different plant species require different moisture levels, meaning that as the pools begins to evaporate around the edges, a distinct zonation of species can be clearly seen.

Vernal pools are a very important ecosystem that are increasingly being threatened. In California alone, more than ninety percent of vernal pools have been lost. There are efforts being made to protect the vernal pools that still exist as their disappearance could also mean the disappearance of important plant and animal species.

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