|Kneiskern's beaked sedge, Knieskern's beaked rush|
|Elizabeth J. Farnsworth|
The following Participating Institutions are custodians for this species in the CPC National Collection:
New England Wild Flower Society
Brooklyn Botanic Garden
The conservation of Rhynchospora knieskernii is fully sponsored.
Elizabeth J. Farnsworth contributed to this Plant Profile.
Rhynchospora kneiskernii is a grass-like plant of the Sedge family that grows only in the Pinelands of New Jersey. A short-lived perennial, the plant inhabits disturbed, open, early-successional wet areas in gravel and clay pits, power-line and railroad rights-of-way, recent burns, muddy swales, and cleared areas. The largest populations occur on natural bog iron deposits in the Pine Barrens. Periodic disturbances and fluctuating groundwater levels appear necessary to perpetuate its existence, as it is a poor competitor with other plants. Thus, succession to shrubs and forest threaten the plant, as well as irreversible disturbances brought by land development, trampling and soil compaction cause by intensive off-road vehicle use, and lowered water levels caused by water withdrawal and drought.
Research and Management Summary:
While little research has been performed directly on this species, a recovery plan has been written for this federally threatened plant. Unfortunately, most populations of this plant are located on private land. However, the U.S. Fish and Wildlife Service has been working to maintain the health of the species through management of federally-owned lands where it is found.
Rhynchospora kneiskernii grows to 60 cm in height, with many slender stems issuing from the base. Its narrow leaves (only 1 to 2 mm wide) often roll inward. Numerous small spikelets of flowers occur at widely separated intervals along the stem. The plant is called "beaked-rush" because the beak at the base of the persistent style is nearly half as long as the 1.3 mm-long fruit (achene) itself.
Distribution & Occurrence
- New Jersey
Rhynchospora kneiskernii occurs in groundwater-influenced, constantly fluctuating, successional environments (USFWS 1993). The plant was once thought to be closely associated with natural bog iron deposits in the Pinelands (Stone 1911), but has now been found in a wider variety of environments. Bog iron forms when slow-moving, acidic stream water leaches iron from the Cretaceous outwash soils characteristic of the Pinelands. Upon contact with oxygen and oxidizing bacteria, the iron mobilizes and is re-deposited in hard layers of "iron stone" in streambeds and adjacent floodplain wetlands. Continual stream erosion and challenging soil chemistry tend to inhibit growth of trees and shrubs that would normally shade out Rhynchospora kneiskernii (USFWS 1997). Six of the 38 known extant populations of the plant occur on this unusual substrate.
Most of the populations, however, have opportunistically colonized newly-disturbed wet areas, including: the edges of abandoned pits and gravel, clay, and sand mines; unpaved roads; railroad beds; utility rights-of-way, and ditches (USFWS 1990). Plant species associated with Knieskern's beaked-rush include: poverty grass (Aristida longispica), warty panic-grass (Panicum verrucosum), and spatulate-leaved sundew (Drosera intermedia), species characteristic of temporarily inundated mineral soils and open areas (Gordon 1993).
Because Rhynchospora kneiskernii typically occurs within wet openings of pitch-pine forest -- a community type established and maintained by fire -- it may be fire-dependent (USFWS 1993). Because fires are now suppressed in much of its habitat, the future of the species and these types of communities is uncertain.
|38 extant populations of Rhynchospora kneiskernii are reported in New Jersey (USFWS 1993). An additional 14 occurrences are considered historic. Population sizes vary from a dozen or so culms to groups covering two acres, and plant numbers vary dramatically year to year, especially as water levels fluctuate in the wetlands they inhabit (USFWS 1991). Thus, the total population level of Rhynchospora kneiskernii is extremely difficult to estimate.|
Conservation, Ecology & Research
Rhynchospora kneiskernii behaves as an annual or a short-lived perennial (U. S. Fish and Wildlife Service 1997). Therefore, its population numbers can fluctuate greatly from year to year.
The plant is a wetland obligate (USDA 2001) and highly intolerant of drought; populations crashed in 1985, a very dry year (USFWS 1991). It thrives best in groundwater-controlled wetlands that undergo period changes in water level, where other plant species are sparse.
This species may benefit from fire, which can revert a wetland to an early successional state and simultaneously provide a flush of carbon and nutrients to otherwise infertile soils.
The U. S. Fish and Wildlife Service (USFWS 1991) reports that pathogens and herbivores are not known to attack Rhynchospora kneiskernii. Foliar silica is produced in a variety of Rhynchospora species and other monocots, and may inhibit browsing by animals.
With small, inconspicuous flowers, the species is likely wind-pollinated. The inflated achenes may be water-dispersed, but this has yet to be substantiated.
Any activities that threaten wetland habitat, hydrology, and water quality in the Pinelands, including: land development, water diversion, road-building, sewage dispos
The U. S. Fish and Wildlife Service has also established agreements with the U. S. Department of the Navy, Federal Aviation Administration, and the New Jersey Division of Fish, Game and Wildlife to protect known occurrences of Rhynchospora kneiskernii (USFWS 1993).
Studies of seed bank dynamics, seed viability, dispersal, and seedling establishment to determine how new populations are initiated and the optimal habitat conditions for plant growth
Controlled burns of selected areas (with appropriate experimental controls) to assess the role of fire in maintaining populations
1988. Protecting the New Jersey Pinelands : A New Direction in Land-Use Management. Piscataway, NJ: Rutgers University Press. 344p.
1998. Pine Barrens: Ecosystem and Landscape. Piscataway, NJ: Rutgers University Press. 684p.