Friday, August 13, 2010

Seep-y and Fen-ish


If you've paddled the upper Jack's Fork since the end of the Pleistocene, you've likely seen the 200 foot high moist limestone/dolomite cliffs that line the river from the Prongs to Alley Spring, rich cliffs loaded with vegetation often associated with fens and seeps in the Ozarks.

In Missouri we have four distinct fen natural community types: prairie fen (cf. Grasshopper Hollow and Kaintuck Fens), Ozark (in which marly fens--those little wet areas at toeslopes on limestone/dolomite glades--are a subtype), forested (rare, only one left in public ownership), and glacial (restricted to the Central Dissected Till Plains). We have two types of seeps, acid seeps (found in the Ozarks and in southeast Missouri on Crowley's Ridge) and saline seeps (never seen one; most abundant in Saline, Pettis, Cooper and Howard Counties--Big Rivers country). The variations that exist between each natural community type are many, based on substrate, availability of (usually mineralized) groundwater, location on the landscape, slope, and other factors. In fact, as is the case with all of our natural community types, fens and seeps can't be described very succinctly, which is why each one consumes 2-4 pages each in the comprehensive book, The Terrestrial Natural Communities of Missouri.


But there's common ground between fens and seeps in the plant communities. Grass of Parnassus can be found in fens as well as some seeps, two species of the elegant yellow flowered Lysimachia are found on seeps and fens alike, and I've seen the white umbellate Oxypolis rigidioron a fen and in a seep. But back to the Jack's Fork, many of the traditional plants of fens and seeps can be found clinging to the side of a moist, weeping cliff face.




I've written once or twice before about the glacial relict plant populations that exist on these moist cliffs, a handful of plants that can be found nowhere else in the state in populations as large as they are on cliffs along the Jack's Fork. In the instances of the rare-in-Missouri Campanula rotundifolia, Aster furcatus and Trautvetteria caroliniensis, the Jack's Fork is the only place you'll find them, plant populations protected by the high, cool, north- and east- facing cliffs and cold water. As climate change occurs as it will, some of these Pleistocene relicts may cease to exist in Missouri.





As you pull your canoe over to a cliff to check out the plants supported by little else but constant seeping water supply and mosses, you may wonder, too, whether these small and restricted areas along the river classify as fens or seeps. These cliff faces harbor a mineralized water source as water percolates through the rock, and many of the plants found here are fen- and seep-loving plants.



It has been decided, not by myself, that the cliff face communities with fen and seep plants found along the Jack's Fork, the Eleven Point and even on parts of the upper Current Rivers are neither fens nor seeps, they're seep-y, but not seeps, and they're fen-like but not fens. These restricted and curious communities are officially classified as a microhabitats of Moist Limestone/Dolomite Cliffs, a community variation within a greater community. According to The Terrestrial Natural Communities of Missouri, moist limestone/dolomite cliffs are "relatively intact because of their inaccessibility to grazing animals. Where grazed by goats, exotic plants have invaded cliff edges and ledges, especially in northern Missouri." Rock climbing and rappelling are particularly damaging to these areas, and overzealous botanists wanting to collect rare plants can also damage the viability of these fragile communities.

2 comments:

Bill said...

I can't remember if it was the Buffalo. No I think it was the Jack's Fork where we smelled a bluff-side flowering, late one afternoon. I've smelled wild grape flower so strong and gaudy that I've craned my neck expecting to see a gaggle of teen girls strolling the lane of a state fair. The bluff-side flowering made me think more of a riverside coming out party, an after dark Monet's La Grenouille. That was years ago. My Pleistocene visualization ability is a work in progress for sure.

Allison Vaughn said...

I bet it was the wild hydrangeas in June...