Credits

Created by Virginia Pellington, Christina Prehn, and Robert Copus, Explore Natural Communities Interns Summer 2016, NatureServe.

Music: Ashton Manor by Kevin MacLeod (incompetech.com). Licensed under Creative Commons: Attribution 3.0.

Photo: Riverside Outcrop Prairie and Barren, by 2016 Summer Interns. Licensed under Creative Commons: Attribution 4.0.

Transcript

Podcast time: 2:59 minutes

The Potomac River falls at Great Falls Park are pretty spectacular to see from the three official overlooks on Patowmack Canal Trail. Here’s a secret: Looking at the sloped riverside landscape just downstream of Overlook 3 is another special view that goes unnoticed. Here, are two globally rare natural community types—plant communities found only on the Potomac and Shenandoah Rivers and nowhere else in the world!  In fact, these communities host more plant species per acre than any other area in the park! These unique natural communities are called the Riverside Outcrop Prairie, and the Riverside Outcrop Barren.

Think of these two communities as a complex mosaic of microhabitats: a mixture of exposed bedrock, patches of shallow soil held tight by the roots of densely growing prairie grasses, and small wetland pockets of plants. The wetland areas host species that require moist conditions to grow. In fact, each of these microhabitats accommodates different specialized species—many species that are not found anywhere else in the park!

While these two natural communities, Riverside Outcrop Prairie, and Riverside Outcrop Barren, have similarities, you can easily see their differences. Scattered throughout the remarkable Riverside Outcrop Prairie, you will find dwarfed white ash  trees and assorted shrubs.  The trees here are stunted—smaller and slower-growing than their counterparts elsewhere. Tree growth is limited by shallow dry soil, as well as harsh elements like severe sunlight, strong winds, and periodic flood and ice scouring. Since larger trees cannot survive in this harsh environment, the floor of this Riverside Outcrop Prairie gets a lot of sunlight. This allows wispy perennial prairie grasses, like Indian grass (Sorghastrum nutans), little bluestem , and big bluestem , to flourish throughout. You can even find them sprouting, against all odds, from the nooks and crevices of the nearly solid rock outcrops in the second natural community here—the Riverside Outcrop Barren! These cracks in the bedrock outcrops also make a good home for wildflowers. You’ll almost always find something flowering in both of these natural communities in the spring, summer, and fall.

One of these incredible, yet, easy to miss, sights is the sticky goldenrod (Solidago simplex var. racemosa)! In Virginia, you can find this critically imperiled plant in only one other county. Here, it grows inconspicuously from small fissures in the massive rocks. But in late summer, you will notice its brilliant yellow blooms—a beautiful sight! These riverside outcrop communities are a truly secret treasure of Great Falls Park.

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