Hi Jason,
I'd like to offer some input on the vernal pool criteria from a biological and ecological standpoint (not touching the hydro- or geological as I know that Spung-Man is the guy for that). My concern is that there seems to be some gray area as to how vernals are defined, so here's my $0.02.
A vernal pool is less defined by its intermittency or hydrology and more defined by the criteria that there is at least one or more species of fauna (with emphasis on amphibians) that relies on a confined body of water for its continued existence, and that continued existence in turn depends on the absence of fish predation. Therefore, the lack of inflow and outflow (preventing fish from entering the pool) is a default part of the criteria.
If I were to challenge the traditional definition of a vernal pool, I'd do it with the following definition: a vernal pool is a miniature ecosystem where the fauna that utilize it does not reside in the pool for the entire year, but migrate from their resident locations to the pool to a) breed (primary) or b) feed (secondary), and the existence of the pool is essential for the breeders.
In terms of breeding, a vernal pool is most clearly identified when it is a body of water where there is the presence of at least one obligate vernal pool breeder. The obligate vernal breeders in the state are the ambystomatid salamanders (marbled, spotted, blue-spotted, tiger, Jefferson), and the wood frog and spadefoot toad. These obligate vernal pool breeders will return to their natal site to breed, and use homing and chemoreception to find the pool. The breeding site fidelity means that destruction of the habitat will remove the breeding site and will seriously inhibit the breeding activity of the population. If you have a confined body of water with an obligate vernal pool breeder breeding, laying eggs, and undergoing full metamorphosis, then you have a vernal pool.
Now for the gray area: another method of identifying a pond as a vernal pool is by the hydrologic criteria (no inflow/outflow, holds water during most of year, etc.) plus the breeding or feeding activity of at least two facultative vernal pool species. There is a long list of facultative vernal pool species, some more rare or threatened than others.
I feel that using the latter definition could potentially set up more challenges for the observer or person reporting a pool. For example: green frogs (L. clamitans, a facultative vernal pool breeder) can breed nearly anywhere. They have a remarkable ability to find water from a long distance away (ask anyone with a backyard pond far from any other water source), and they are very much generalists in their selection of breeding habitat (I've seen them breeding in the holes created by fresh blowdowns). It would not be unreasonable to find green frogs sitting in the water in a tire rut. It would also not be unreasonable for a water snake (another facultative vernal pool species) that is crossing between two wetlands to stop in the tire rut to feed on a green frog. That being said, I don't think that this should qualify the tire rut as a vernal pool. It loosens the definition and adds dimensions that may complicate the conservation efforts down the road.
Now for even more gray area: the tire rut becomes a vernal pool if an obligate species breeds there, but if two facultative species are found breeding there, such as green and bull frogs, should this and does this qualify the tire rut as a vernal pool? It is a confined body of water, it has no inflow or outflow, it has two facultative vernal breeders present, and it holds water during the crucial seasons of the year-is this a vernal pool? I'd question it, because of the ability of green and bull frogs to breed nearly anywhere.
Now let's change the scenario and say that I observed the full development and metamorphosis of Fowler's toads and Pine Barrens tree frogs in the tire rut, I would propose that this a vernal pool. Why? Because the Pine barrens tree frogs are more sensitive to habitat disturbance, are endangered, and because both of these species are less of a 'habitat generalist' than the green and bull frogs (although I admit that Fowler's toads can be pretty resourceful when breeding as well). In short, I believe that they will rely on this body of water more than green or bull frogs would. I think that it helps to make these kinds of distinctions when labeling a body of water as a vernal pool.
Interested in hearing your thoughts,
Chilehead
I'd like to offer some input on the vernal pool criteria from a biological and ecological standpoint (not touching the hydro- or geological as I know that Spung-Man is the guy for that). My concern is that there seems to be some gray area as to how vernals are defined, so here's my $0.02.
A vernal pool is less defined by its intermittency or hydrology and more defined by the criteria that there is at least one or more species of fauna (with emphasis on amphibians) that relies on a confined body of water for its continued existence, and that continued existence in turn depends on the absence of fish predation. Therefore, the lack of inflow and outflow (preventing fish from entering the pool) is a default part of the criteria.
If I were to challenge the traditional definition of a vernal pool, I'd do it with the following definition: a vernal pool is a miniature ecosystem where the fauna that utilize it does not reside in the pool for the entire year, but migrate from their resident locations to the pool to a) breed (primary) or b) feed (secondary), and the existence of the pool is essential for the breeders.
In terms of breeding, a vernal pool is most clearly identified when it is a body of water where there is the presence of at least one obligate vernal pool breeder. The obligate vernal breeders in the state are the ambystomatid salamanders (marbled, spotted, blue-spotted, tiger, Jefferson), and the wood frog and spadefoot toad. These obligate vernal pool breeders will return to their natal site to breed, and use homing and chemoreception to find the pool. The breeding site fidelity means that destruction of the habitat will remove the breeding site and will seriously inhibit the breeding activity of the population. If you have a confined body of water with an obligate vernal pool breeder breeding, laying eggs, and undergoing full metamorphosis, then you have a vernal pool.
Now for the gray area: another method of identifying a pond as a vernal pool is by the hydrologic criteria (no inflow/outflow, holds water during most of year, etc.) plus the breeding or feeding activity of at least two facultative vernal pool species. There is a long list of facultative vernal pool species, some more rare or threatened than others.
I feel that using the latter definition could potentially set up more challenges for the observer or person reporting a pool. For example: green frogs (L. clamitans, a facultative vernal pool breeder) can breed nearly anywhere. They have a remarkable ability to find water from a long distance away (ask anyone with a backyard pond far from any other water source), and they are very much generalists in their selection of breeding habitat (I've seen them breeding in the holes created by fresh blowdowns). It would not be unreasonable to find green frogs sitting in the water in a tire rut. It would also not be unreasonable for a water snake (another facultative vernal pool species) that is crossing between two wetlands to stop in the tire rut to feed on a green frog. That being said, I don't think that this should qualify the tire rut as a vernal pool. It loosens the definition and adds dimensions that may complicate the conservation efforts down the road.
Now for even more gray area: the tire rut becomes a vernal pool if an obligate species breeds there, but if two facultative species are found breeding there, such as green and bull frogs, should this and does this qualify the tire rut as a vernal pool? It is a confined body of water, it has no inflow or outflow, it has two facultative vernal breeders present, and it holds water during the crucial seasons of the year-is this a vernal pool? I'd question it, because of the ability of green and bull frogs to breed nearly anywhere.
Now let's change the scenario and say that I observed the full development and metamorphosis of Fowler's toads and Pine Barrens tree frogs in the tire rut, I would propose that this a vernal pool. Why? Because the Pine barrens tree frogs are more sensitive to habitat disturbance, are endangered, and because both of these species are less of a 'habitat generalist' than the green and bull frogs (although I admit that Fowler's toads can be pretty resourceful when breeding as well). In short, I believe that they will rely on this body of water more than green or bull frogs would. I think that it helps to make these kinds of distinctions when labeling a body of water as a vernal pool.
Interested in hearing your thoughts,
Chilehead
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