Recently I had a chance to take a guided walk with Zach from the Virginia Department of Conservation and Recreation's Natural Heritage Program at Grafton Ponds Natural Area Preserve (NAP). I've talked about Grafton Ponds several times in the past, most recently this past spring when I did a bird walk with some friends.
The walk was in celebration of the 40th anniversary of the Natural Heritage Program and one of several they are doing around the state. Grafton Ponds is special because it has a large number of sinkhole depressions that collect water and then dry out annually. Sometimes called vernal pools or ephemeral ponds, this cycle of wet and dry throughout the year provides good places for amphibian to lay eggs. Fish are one of the main predators on tadpoles and eggs. Since the ponds dry out, the fish can't survive so there are fewer predators for the young amphibians to deal with. There are approximately 200 such ponds in Grafton Ponds complex with about 70 or so in the Natural Area Preserve proper. Depending on the water level, there may be three nearby ponds or a single, larger pond, making it hard to get a precise count.
The ponds form when water collects and slowly seeps through bedrock that is dissolvable. Often that is limestone. Here on the coast, the bedrock is fossilized shells from a few million years ago, part of the Yorktown formation. Appropriate since the preserve is just outside Yorktown. The ponds continually form as the bedrock is removed and fill in as more sediment fills in the ponds. Zach told us that some of these ponds have been dated to 40,000 year ago while younger ones are around 350 years old. The older ones have a lot of spruce pollen in the sediment dating from the last ice age when spruce could live here. The younger ones formed around the end of a dry era that coincided with the arrival of European settlers. The settlers at Jamestown and other early colonies had trouble finding sufficient fresh water and that is attributed to salt-water intrusion to aquafers due to the extended dry period. As the rains returned, ponds started forming again. The Europeans also removed a lot of trees. The trees pulled up a lot of rain water. Fewer trees means more water to dissolve the shells and make sinkholes.
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| Some fossilized shells found along a stream bed |
To access the preserve, we walk along an old road through the back part of Newport News Park. After going through some terrain (or what passes for terrain in coastal Virginia) we reach a broad flat area and this is where the ponds and preserve start. Along this road we see a lot of pawpaw saplings and find a few white crownbeard plants.
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| Now entering the Natural Area Preserve |
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| Pawpaw saplings forming the understory |
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| White crownbeard, Verbesina virginica |
Zach led us to Burn Pond, maybe named for a wildfire in the distant past, and showed us how there are different plant species in concentric rings based on how often and for how long the area dries out as the water recedes through the year. The group spread out looking for fascinating finds. I found this cool looking stump on the edge of the currently dry pond. Others found a marbled salamander and a wolf spider carrying its babies.
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| Artistic stump? |
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| Marbled salamander |
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| Wolf spider nursery |
Our final stop of the day was at a pond spice bush. This species was originally collected by the locally famous botanist John Clayton. Through a series of sending samples on, his samples ended up in Linnaeus' hands and appeared in some of Linnaeus' early taxonomy publications. Pond spice bush is a more southern plant and only a few populations are known in Virginia, Grafton ponds having one of them. A fun aspect of this bush is that it flowers before the leaves come out in the spring. The flower buds are already showing here in early fall.
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| Pond spice bush flowers for next year |
After a gray week with a nor'easter stalled out just off the coast causing a lot of tidal flooding and heavy grey skies, it was nice to get out for a walk in a special space. The winds were calmer and it was brighter if not yet sunny. And I learned some new things, especially about plants in this unusual ecosystem.
'Til next time, enjoy the outdoors wherever you are. If you like what you read here, consider subscribing to blog announcements over on the right.
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