Wetlands and Seeps

An herbaceous wetland in Manassas National Battlefield Park.

NPS Photo

Wetlands are vitally important habitat for a wide variety of plants and animals in the park. Some trees can survive in areas that are wetter, and outcompete other trees. Some amphibians depend on seasonal pools of water to raise their young.

Over 200 acres of wetlands are mapped at Manassas National Battlefield, including both forested and herbaceous wetlands. The main difference between forested and herbaceous wetlands is the presence of a forest canopy. Forested wetlands, or vernal pools, often flood for part of the growing season and are home to flood-tolerant species of trees. Herbaceous wetlands are non-forested seasonal pools that fill in the spring and dry up in the summer.

Changes in rain and snow from one year to the next can cause wetlands to grow or shrink. Over time, some herbaceous wetlands are changing into forested wetland as water-tolerant trees become established. Herbaceous wetland plants respond relatively quickly to any changes in hydrology, whereas a forest may take decades to change as slow-growing trees compete for resources.

 

Vernal pools are seasonal ponds that offer excellent habitat for amphibians such as frogs and salamanders.

NPS

Vernal Pools

Among the most interesting wetlands are vernal pools. Vernal pools are shallow depressions that retain water only during certain times of the year. These small, isolated wetlands usually fill with water in the spring when snow melts and rainfall accumulates before being soaked up by thirsty tree roots or draining into the Chesapeake Bay Watershed.

The time it takes the vernal pool to dry out depends on the depth of the depression, soil permeability, and inches of rainfall. Due to the fact that vernal pools are only temporary, they cannot support fish.

Vernal pools make a wonderful breeding ground for amphibians, which can mate and lay eggs with little or no fear of predators. Because of this, nearly fifty percent of amphibians in North America breed primarily in vernal pools.

The spotted salamander, Ambystoma maculatum, is an excellent example of an interesting creature that could not survive in Northern Virginia without vernal pools to breed in. An egg mass containing roughly two hundred eggs is laid on plant debris in the vernal pool's waters in early spring. Shortly after, the eggs hatch into larvae that grow and develop in the vernal pool while feeding on zooplankton and insect larvae. When they reach maturation, the spotted salamanders live a covert lifestyle, eating insects and remaining hidden in moist places underground or nestled under wet logs and rocks.

Vernal pools may look like just a puddle to some; however, upon further inspection, one would find that they are an important habitat that is crucial to the delicate life cycle of frogs, salamanders, turtles and other creatures. Manassas National Battlefield is an important natural resource refuge that is an asset to the public and the environment. The Stone Bridge loop trail's boardwalk ascends over a vernal pool, providing a great viewing opportunity for visitors.

 

References

Loomis, D.T. and K.E. Heffernan. 2003. Classification and Mapping of Wetlands at Manassas National Battlefield Park, Virginia: Brawner Farm and Matthews Hill Tracts. Natural Heritage Technical Report 03-21. Virginia Department of Conservation and Recreation, Division of Natural Heritage, Richmond, VA. Unpublished report submitted to the National Park Service. 8 pp.