A Honey of an Anklet

Saturday, Paula DePriest led a workshop of mostly frozen participants to Carderock on the Maryland side of the river. Our subject: rock and tree lichens (the soil lichens being inaccessible due to snow cover). Soil, rock, or bark is only the substrate (although certain species do have a preference); the lichen gets no nourishment from it. In all cases, sugars are generated by algae held in the body (thallus) of the lichen, which comprises a fungus. Depending on your point of view, the alga is a captive of the fungus or (Dr. DePriest’s preference) is domesticated by the fungus.

Rocks in this area often are commonly home to a Mid-Atlantic specialty, Flavoparmelia baltimorensis. It’s the pale yellow-green (yellow to a lichenologist) lichen at the lower left of this badly-focused image, along with Lepraria sp. at the right and Pertusaria sp. at the left.

The olive-ish color and black specks of Porpidia sp. are fairly easy to learn. This individual is about 4cm across, as you can see from the scale card.

The relatively bright yellow of Candelariella sp. is also easy to find. This crustose lichen goes by the common name of Egg Yolk Lichen.

This Punctelia rudecta, a foliose lichen, was found on bark. The tiny punctuations in the lichen’s thallus, and the dark isidia surrounding them, don’t read in this image.

The good news is that there are about three dozen taxa of lichens of interest in the D.C. area. You can write a key (as Dr. DePriest has) to all of them that takes up only two pages. The bad news is that you need at least a hand lens to apply the key.

Construction is complete for the wetlands restoration project at Huntley Meadows Park! Some additional planting and trail work remains, but the period of monitoring and maintaining has begun.

Park manager Kevin Munroe led a special-access “backstage” mini-tour of the dam and water control structure for a group of volunteer staff on Saturday. Working backwards, as it were, this is a view of the outflow into Barnyard Run. As you can see, everything is still rather raw and artificial looking. The sine wave-like curves of this stream haven’t yet been naturalized to a messier state. Kevin says that the park will take an “adaptive management” approach to the project. If the beavers drag one log across this watercourse (beavers abhor moving water), it won’t necessarily be removed.

The water control structure itself is disguised as an observation platform, via the addition of the protective railing. At left, a view upstream, looking at the main wetland. At right, water flows right to left through the baffles and chambers of the structure, through a buried concrete culvert, into the outflow.

Manholes for easy (depending on what you think “easy” means) access to the interior of the structure, for cleaning out debris.

The observation platform itself, accessible from the South Kings Highway side of the park via the hike-bike trail and a new stone dust trail, is obscured from view from the main observation tower and boardwalk by an artificial knoll. Even though it’s possible to access the dam and water control structure from the boardwalk side of the park, this is discouraged by management, for a number of reasons I won’t go into here. But making the platform and tower mutually invisible makes the crossing less tempting.

The working part of the dam is an interlocking wall of vinyl sheet pilings. All you can see of the wall is the plastic strip that runs along the top, the straight white line in this image. From an engineering and hydrology standpoint, the earthen berm enclosing the dam on both sides is unnecessary: it’s purely for naturalization. (Cf. the unsheathed impoundment walls that you see on many National Wildlife Refuges.) The ground has been planted with native grasses and vines, and the hope is that by summer the dam and its berm will be covered with chest-high grass and access-dissuading, thorny greenbrier and raspberry canes. Something to check back on in a few months.

Something else to look for in the future: A few trees have been caged in metal fabric to prevent beavers from taking them down—there’s a Red Maple right next to the “phoebe bridge.” Soon, you will see more trees thus caged, but these are trees that park staff understand will be killed by inundation as water from the project finds its new level. These will become snags, standing dead trees that serve as habitat for all sorts of organisms, and are thus valued by foresters.

There’s a great photoset of work-in-progress images curated by the Park Authority. In particular, you can see the interlocking sheets that make up the dam, before they were covered in dirt.

Leta was a good sport and went along with me on a New Year’s Day walk in Great Falls Park. I hadn’t expected that the trails would be muddy (we were just wearing sneakers, on our way to a party at Tel’s), so we picked our way more carefully than usual. And once we’d been to the Matildaville ruins (always a bit of a letdown), I hadn’t expected that Leta would want to scooch down the river trail. But we did, and I found some nice patches of Wild Oats to show her. And I think that my mystery plant, still in fruit, was Sweet Cicely.

She liked the floods marker post.