‘vernal’ pools

In 2011, I applied for and received grant funding to implement a number of conservation and habitat improvement measures on my land. The funding came from the Conservation Stewardship Program (CSP), which is administered by the Natural Resources Conservation Service, a branch of the U.S. Department of Agriculture. If approved for funding, CSP activities are carried out over a five year period, and encourage a broad range of stewardship measures. In my case, as nearly the entirety of my land is forested, the focus of my Conservation Plan (which defines and guides the implementation of the program) is woodland habitat improvement, including such measures as:

  • Forest stand improvement for wildlife (creating or conserving snags and/or den trees), and for soil quality (erosion control);
  • Forest wildlife structures (brush piles, bat houses, nest boxes, etc.);
  • Hardwood crop tree release;
  • Restoration of rare or declining habitat;
  • Riparian forest zone enhancement;
  • Creation of shallow water habitat

The great thing about this program—-and other similar federal programs such as the Environmental Quality Incentives Program (EQIP) and the Wildlife Habitat Incentive Program (WHIP), among others—-is that you are being paid to do things on your land that 1) you may have been doing already; or 2) you always wanted to do but couldn’t justify or prioritize the  expense. For me, this was particularly true with the construction of shallow water habitat, otherwise known generally as ‘vernal’ pools.

A ‘vernal’ pool is an ephemeral body of water that provides critical (and often lacking) breeding habitat for a diversity of species. I place the vernal in quotes because it refers to springtime, when such pools are commonly full when found in the open, and are most necessary for breeding (ver is spring in Latin); in reality, when found in woodlands, these pools are often equally full in the fall, depending on the rainfall in a given year. So a more accurate term in this case is woodland or seasonal pool.

In any event, there are a few key features that distinguish this type of aquatic habitat from others that may be present nearby:

  1. They periodically dry up, but are generally full for at least 90 days from late winter through mid-spring;
  2.   They are lined with at least a semi-impermeable base, preferably of clay or silty loam, in order to temporarily hold the rain, snowmelt, surface runoff, or seasonally high groundwater that fills the pool;
  3. They contain no fish, which if present would prey voraciously on  breeding aquatic organisms, such as occurs in a permanent pond;
  4. They average 6-30″ deep maximum, with varied topography, and contain a variety of organic materials (ie–leaf litter, stumps, roots, logs, rocks, etc.) to add habitat complexity, in addition to 30-50% coverage with aquatic vegetation.

While my land has a small creek running through it, as well as a permanent man-made pond (which harbors a population of introduced smallmouth bass), neither offer the unique combination of traits that define a seasonal pool.  While perhaps most essential in the life cycles of reptiles, amphibians, and insects—they have been called the ‘coral reefs of Northeastern forests’ for their ability to support and sustain life, and are estimated to provide breeding habitat for half of all frog species and one third of all salamander species where present—seasonal pools can also provide an important water source for a variety of mammal and bird species during times of drought, or in areas where surface water is otherwise nonexistent.

Here is a site in my woodlot that I chose for one of the pools:

vernal  pool location

I chose this spot as the soils in this area remain wet throughout the year due to periodic surface runoff from above, as well as from a number of springs that flow even during dry spells. There is a fair amount of clay in the soil as well. The carpet of Spotted jewelweed (Impatiens capensis) in the photo is indicative of moist, rich soil (as are the Sugar Maple, Basswood, and White Ash in this forest stand).

It helps to know someone with a bulldozer, such as my neighbor who was kind enough to help out:

bulldozing vernal pool

bulldozing vernal pool

completed vernal pool

He first dug out the rough shape to an approximate depth, then created, compacted, and graded the berm that impounds the pool, leaving one side of the berm slightly lower than the rest to serve as a spillway to handle any overflow during times of high water. This all took place in August. A few weeks later, following a good rain, I went back up the hill with my camera and found this:

vernal pool full

There were wood frogs leaping in and splashing around as I approached. Build it, and they will come, as the saying goes.

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