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A Year in the Life of Pimmit Run: Winter Wetlands

Wetlands are always special, but particularly in the dead of winter when they develop a unique character. The Pimmit Run Stream Valley paths I frequent contain numerous federally designated wetlands. Starting from Old Dominion Drive, just below the McLean Community Business Center (CBC), exist a series of wetland areas as Pimmit Run flows and weaves its way toward the Potomac River (see map from the National Wetlands Inventory at the end of this blog).

How special is this? Very. Wetlands are highly productive ecosystems, with special soils, and plants, and host an immense variety of vital species. Even though much of the vegetation along the trail stretch in the middle picture above is not native, the entire area is thick with birds and small creatures that can be heard if not seen.

As one approaches the foot of Brookhaven Drive, the shallow stream wetland area widens. This is where a Great Blue Heron can frequently be spotted as it comes to rest and hunt and where beavers recently built a dam on top of the stepping stone trail in a futile attempt to stem the stormwater rapids that follow rainfalls (the dam was washed away by stormwater after a few months).

Across the stream, the well-established trail follows Pimmit Run on the east, flanked by a large wooded upland area, covered on its north-facing slopes with lush stands of Kalmia latifolia (Mountain Laurel). The trail weaves along the wooded floodplain and around the upland area, where the terrain flattens out and one enters another wide wetland area that is rich with vernal pools in late winter.

Today, as I trek along this portion of the trail in early January, I am struck by the stark view of nature it presents. Fallen trees, which appear in vastly greater abundance due to the increasing ferocity of the stormwater runoff during rainfalls, cover the ground, give the appearance of vast destruction while simultaneously providing safe spots for wildlife to burrow (looking at the bright side). Along this stretch also lie numerous vernal pools, essential breeding habitat for frogs and salamanders. Today I observed a strange orange glow in one of the vernal pools -- hopefully not toxic!

This is the time of year when the few spots of native evergreen really stand out. So far this month I have observed (pictured below, clockwise) Tipularia discolor (Crane Fly Orchid), Chimaphila maculata (Winterberry), Geum canadense (White Avens), Polytrichum commune (Hair Cap Moss), lots of Carex spp. (likely Carex platyphylla, Carex plantaginea, or Carex blanda). Kalmia latifolia (Mountain Laurel), and (not pictured) Ilex opaca (American Holly), and Polystichum acrostichoides (Christmas Fern).

The unique ecology and topography of this area has given rise to a number of associated native plant communities -- a topic for next time.


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