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Sensitive joint-vetch Listed: 5/20/1992 Status since listing: Unknown The sensitive joint-vetch (Aeschynomene virginica), a large annual plant in the bean family, was named for its leaves, which fold slightly when touched [2]. It grows in intertidal zones on the Atlantic coast from New Jersey to North Carolina that are flooded twice daily but are far enough upstream to have nearly fresh or barely brackish water chemistry [3]. Growing sites have bare to sparsely vegetated substrates, including accreting point bars that have not yet been colonized by perennial species, low swales within extensive marshes, or areas where muskrats have eaten most of the vegetation [1]. It is often found in the estuarine meander zone of tidal rivers where sediments transported from upriver settle out and extensive marshes are formed. Historically, the sensitive joint-vetch was known from New Jersey, Delaware, Pennsylvania, Maryland, Virginia and North Carolina, but no longer found in Delaware or Pennsylvania [2]. Currently, there are 26 known populations, including three in Maryland, one in New Jersey, two in North Carolina, and twenty in Virginia [4]. The species' decline was caused by habitat destruction [1]. Many of the marshes where it occurred historically have been dredged and/or filled and the riverbanks stabilized with bulkheads or riprap [1]. It continues to be threatened by road construction, residential, commercial and industrial development, water pollution, bank erosion, and motor boat traffic [3]. Virginia. Sensitive joint-vetch is most abundant in Virginia, with 20 populations occurring along six rivers [3]. Populations occur on the Potomac, Rappahanock, Mattaponi, Pamunkey, Chickahominy and James rivers [2]. A comprehensive survey conducted in 1987 found an extensive population along approximately 25 miles of the Rappahannock River [4]. Another large population was found along approximately 15 miles of the Mattaponi River and a third large population was documented along a 15-mile stretch of the Pamunkey River [4]. Three smaller populations (<50 individuals) were found along the other three rivers [4]. In 2000, the sensitive joint-vetch was rediscovered at the Colonial Natural History Park where it had last been seen in 1938 [5]. Approximately 15 plants were found near the 1938 site and as of 2004 the population appeared healthy with over 200 plants observed [5]. The expansion of this population could be due to two seasons of unusually high rainfall, which reduced water salinity [5]. Most remaining Virginia populations occur in areas potentially threatened by proposed water withdrawal projects, filling, erosion, impoundments, and commercial and residential development [4]. Maryland. There are three extant sensitive joint-vetch populations in Maryland [4]. The largest, with over 1,000 individuals, is in the Princess Anne Marshes on Manokin Creek in Somerset County [4]. Population counts surveys in 1991 and 1992 suggested this population was stable [4]. Two other smaller populations were rediscovered in 1994 in Calvert and Prince Georges counties [4]. New Jersey. The only remaining population occurs on the Manumuskin River in Cumberland County [4]. This site is partially located within The Nature Conservancy’s Manumuskin River Preserve, and represents one of the few remaining examples of pristine freshwater tidal marsh habitat in the state. It is one of only two joint-vetch sites (the other is in Virginia) across the entire range of the species that is afforded adequate habitat protection [1]. The number of vertical stems counted increased from 229 in 1982 to over 10,000 in 1994 [4]. However, in 1993, Phragmites australis, an invasive plant that had been found near the site had expanded rapidly and could become a problem [4]. The Nature Conservancy has started a program to try to remove this invasive species [3]. This site could also potentially be threatened by a proposed highway (Route 55 extension) and power plant [4].North Carolina. In 1990, sensitive joint-vetch occurred only in two ditches connected to Lake Mattamuskeet in Hyde County [4]. These man-made habitats were thought to be temporary and populations were not considered viable [4]. Surveys conducted in 1985 did not find sensitive joint-vetch at any other historic North Carolina locations [5]. [1] U.S. Fish and Wildlife Service. Species Description: Sensitive Joint-vetch in North Carolina. North Carolina Ecological Services. Website accessed, (http://nc-es.fws.gov/plant/sensjointv.html) |
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