Tuesday, August 16, 2016

Shenandoah sinkhole ponds

Virginia Sneezeweed (Helenium virginicum) is a federally-listed "threatened" species associated with Shenandoah Valley sinkhole ponds in Virginia. A number of years ago, the species was also confirmed in Missouri in similar habitat, creating "one of the great phytogeographic mysteries of the Eastern North American flora" (1).

Virginia Sneezeweed (Helenium virginicum)

Large patch of Virginia Sneezeweed along margin of sinkhole pond, Augusta County, VA


This is a seed-banking species whose populations fluctuate widely at a given site. Flowering stems can become prolific and abundant under the right conditions (2) (image left)

Water levels in the sinks vary widely and fluctuate seasonally. The example shown below held over 12" of water while immediately adjacent ponds were completely dry.  Not surprisingly, the vegetation may also be quite variable both seasonally and between sites. For more detailed descriptions see (3) & (4) below.

Shenandoah sinkhole pond with standing water (July 12, 2016)
Note: Pin Oak (Quercus palustris) overhanging branch  

Shenandoah sinkhole pond, same site as above (August 04, 2016)
standing water still present, emergent Persicaria and Polygonum spp. superficially dominant
Shenandoah sinkhole pond with Buttonbush (Cephalanthus occidentalis) and emergent Eriocaulon

The sinkhole ponds are biologically important features of the Shenandoah Valley region and they support many other species in addition to Virginia Sneezeweed. These ponds are also extremely important for dragonflies (5) and reptiles and amphibians (4), in part, because the ephemeral water levels often restrict predatory fish populations.
Spotted Turtle (Clemmys guttata) - the only populations west
of the Blue Ridge are found in sinkhole ponds (4)
Image from coastal plain of VA
Amphibian egg masses in sinkhole pond (03-23-16)

Dragonfly exuvia on Lowland Loosestrife (Lysimachia hybrida)
in sinkhole pond, Augusta Co

Lowland Loosestrife (left) is considered significantly rare in Virginia, and known from a handful of sinkhole ponds.

A number of other rare plants may also be found:

Boltonia montana  - Augusta Co., VA (08-4-16)

Valley doll's daisy (Boltonia montana) is an extreme global rarity, known from 4 VA sites, all within a few miles of one another in Augusta County's sinkhole ponds. Described as new to science in 2006, this species also has an unusual phytogeographic pattern.

Northern St. John's Wort (Hypericum boreale)  -- Significantly rare in Virginia; known from Shendandoah sinkhole ponds and disjunct to interdunal ponds near the coast.

The ponds themselves are globally-rare and imperiled, In the two examples shown below, one has been artificially deepened and stocked with fish and the other used as a mini-landfill.

It's hard to image more important and special habitats. I hope to be able to play a small part in protecting them.

(1) Virginia Plant Atlas: http://vaplantatlas.org/index.php?do=plant&plant=2129
(2) Draft Recovery Plan:  https://www.fws.gov/ecos/ajax/docs/recovery_plan/001002.pdf
(3) Descriptive Ecology: http://virginianaturalhistorysociety.com/banisteria/pdf-files/ban13/Ban_13_Buhlmann_Mitchell_Smith.pdf
(4) See Montane Depression Wetland types and links here (http://www.dcr.virginia.gov/natural-heritage/document/comlist07-13.pdf)
(5) A new species of Boltonia....SIDA 22:873-886.

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