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Vernal Pools: Critical Woodland Habitats

Posted: March 24, 2014

For many, spring is found in wetlands and vernal pools.

After a long winter, signs of spring are showing in woodlands across Pennsylvania. Obvious indicators are swelling tree buds, especially red and silver maple, corn snow patches remaining where deep drifts were, and in yards, daffodil, crocus, and tulip leaf tips pushing into the warming spring air.

For many woodland owners and visitors, spring is found in wetlands and vernal pools. One of the first spring woodland flowers depends on wetlands. The careful observer will take delight in finding hooded skunk cabbage flowers melting the snow around them (yes, they actually create their own heat) and showing their purple and white-spotted hoods.

The real spring show stopper is the vernal pool. In the spring, these shallow pools, filled with spring snow melt and higher water tables, become meccas of activities as many of the state’s amphibians migrate to them to breed. On late winter and early spring nights, salamanders, toads, and frogs that have traveled from nearby upland sites provide astonishing shows as they create springtime “dances” in woodland vernal pools. It is important to understand that many of these species are struggling with habitat loss and degradation and their survival depends on making good decisions as we manage, use, and change woodlands and affect associated wetlands and water resources.

Vernal pools, which are seasonal wetlands, and their surrounding landscape represent unique and threatened ecosystems. Depending on the time of the year and your experience in recognizing characteristics associated with these pools, it is sometimes easy to overlook them. Statewide, these isolated seasonal wetlands, which do not connect to other water bodies, are very vulnerable to disturbance. Key among these threats are habitat loss in the uplands surrounding pools, changing water levels and quality, debris accumulation, habitat fragmentation, vegetation changes, and climate change.

Studies have shown that many of the species dependent on vernal pools for at least part of their life cycle spend most of their lives within 1,000 or so feet of their birth site – in that pool. So, it is critical to protect or improve conditions around their pool. For example, development that involves land clearing or felling trees might increase solar gain on the pool, changing water temperatures. Compacted soils and disturbed forest floor leaf litter remove habitat and change water flow through the soil, and might reduce water depths and change water chemistry. The installation of a street curb or a rut created by vehicle traffic near the pool becomes an insurmountable barrier. Soil erosion sediment or debris from felling trees or construction easily fill the pool and reduce or increase water levels.

Sometimes we all fail to realize how various species depend on small parts of our environment. Forests are a dominant land cover in Pennsylvania. Woodlands with wetlands and especially vernal pools are much less common and becoming even less prevalent as we use and change land. Species that depend on water, especially seasonal water, and woods are particularly limited in how they can adapt and change. Many of these species have very high fidelity to their birth pool and will even move past a suitable site looking for that special place. We need to help them survive by taking care of their critical habitat.

The Pennsylvania Natural Heritage Program, a partnership formed by The Western Pennsylvania Conservancy, The Pennsylvania Department of Conservation and Natural Resources, The Pennsylvania Fish and Boat Commission, and the Pennsylvania Game Commission, has an amazing website with outstanding information on the condition of our state’s natural resources . If you are unfamiliar with it, go look, and explore all it has to offer. Especially, look at the link to vernal pools under the “Resources” tab. This is an amazing website and it is fun and easy to navigate and read.

Spend some time learning about Pennsylvania’s precious natural resources and consider how you can protect our vernal pools. If you happen to have a vernal pool on property you own or visit, you will find a very helpful vernal pool management guide on the website, which will likely become a valuable resource as you care for these important resources.

The Pennsylvania Forest Stewardship Program provides publications on a variety of topics related to woodland management. For a list of free publications, call 800-235-9473 (toll free), send an email to RNRext@psu.edu, or write to Forest Stewardship Program, Natural Resources Extension, The Pennsylvania State University, 416 Forest Resources Building, University Park, PA 16802. The Pennsylvania DCNR Bureau of Forestry and USDA Forest Service, in Partnership with Penn State’s Department of Ecosystem Science and Management, sponsor the Forest Stewardship Program in Pennsylvania.