Pennsylvania Tree Farm: The Importance of Vernal Pools in the Forest Ecosystem

The two clusters of seven vernal pools about a half-mile apart on the Bald Eagle Mountain were constructed in 2016 and 2017. Previously, there never were any nearby wet areas other than temporary spring seeps that quickly dried up after rains. The 7-degree slope of the mountain where the pools were constructed had previously been a dry slope not capable of retaining water. The only water came from a combination of rain and snowmelt. So, it surprised me to see the abundance of spring peepers, tree frogs, and various species of salamanders migrate from other equally dry parts of the mountain to inhabit these pools. It also was equally surprising to see how each pool was selectively colonized by different species. The spring peepers selected their own pool and don’t seem to be present in others. All of this life was below the surface of the water at some point in their lifespan, which of course was the purpose of constructing them. However, there was more to come.

Last year was a dry year in Central Pennsylvania. It became noticeable from the tracks in the muddy perimeters of the pools that other wildlife was visiting the vernal pools for access to a water source. The pools were built as shallow basins in clay soils present in this area. Since they were constructed, they have not completely dried up, even though there is no supply of water to them other than periodic rainfall. So, ducks frequently visiting some of the pools is not surprising. Numerous dragonflies and damselflies patrol the surfaces of the pools and effectively control the mosquito populations. But much larger animals also visit the pools. The game cameras have photographed deer, raccoons, mink, fishers, bear, and a variety of forest birds. Some photographs show as many as a dozen deer at one time. Recently a Red-tailed Hawk also visited.

These shallow water sources are used by many types of wildlife, and their presence enhances the habitat to aid in supporting their abundance on the Tree Farm, which is one of the forest management objectives. Last month a wildlife biologist familiar with the property and its recent forest habitat history, placed autonomous monitoring units (called AMUs) on the property to attempt recording the Eastern Whip-poor-will. While on the property, in two hours he identified 45 different woodland birds attracted by the early successional habitat areas.

If you are interested in seeing more on these vernal pools, a recent set of videos about the Tree Farm were recorded by ClearWater Conservancy last fall. The fourth video on the list covers the shallow water vernal pools. This video and six more on additional forest management subjects on the Tree Farm that may also be of interest can be found at www.clearwaterconservancy.org/forest-tour.

For more information about the PA Tree Farm program, visit our webpage at www.paforestry.org/treefarm.

By John Hoover, PA Tree Farm Committee Chair