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Plant Profile

Knieskern's Beaksedge (Rhynchospora knieskernii)

Rhynchospora kneiskernii growing with Xyris torta Photo Credit: Uli Lorimer

Global Rank: G2 - Imperiled
Legal Status: Federally Threatened
Family: Cyperaceae
State: DE, NJ
Nature Serve ID: 134727
Lifeform: Graminoid
Date Inducted in National Collection: 04/04/1991

Description:

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. Plant Description: 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.

Where is Knieskern's Beaksedge (Rhynchospora knieskernii) located in the wild?

Habitat:

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.

Distribution:

Rhynchospora kneiskernii is known only from New Jersey in Atlantic, Burlington, Camden, Monmouth, and Ocean Counties in the heart of the Pinelands. Populations were previously known from Camden Count

States & Provinces:

Knieskern's Beaksedge can be found in Delaware, New Jersey

Which CPC Partners conserve Knieskern's Beaksedge (Rhynchospora knieskernii)?

Brooklyn Botanic Garden

Conservation Actions

09/27/2020

Seed dried and stored under seed bank conditions for four years between 1991 and 1995 germinated successfully in 1995, demonstrating that the species is capable of seed-banking.

09/27/2020

Nature Serve Biotics

05/02/2017

This species is now endemic to 5 counties within the New Jersey Pine Barrens, where fewer than 40 recent occurrences have been documented. Most of these are in artificially disturbed habitats located on unprotected lands. Many of these populations are declining due to woody succession of the habitat or through impacts associated with over-use by recreational vehicles, fire supression, roadside scraping, and other incompatible land uses. Very few occurrences occur on adequately protected lands or in habitats where natural disturbance regimes remain intact. The species was collected from 2 locations in Delaware, but it has not been documented in that state since 1875 and is presumed extirpated.

Elizabeth J. Farnsworth

01/01/2010

As identified by U. S. Fish and Wildlife Service 1991 & 1993, threats include: Any activities that threaten wetland habitat, hydrology, and water quality in the Pinelands, including: land development, water diversion, road-building, sewage dispos

Elizabeth J. Farnsworth

01/01/2010

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.

Elizabeth J. Farnsworth

01/01/2010

The New England Wild Flower Society (Framingham, Massachusetts), has conducted seed germination trials on this species. Moist, cold stratification enhances germination. Seed sown after collection in 1991 germinated and produced plants. These plants flowered in two consecutive years, confirming that the plant can be a short-lived perennial. Seed dried and stored under seed bank conditions for four years between 1991 and 1995 germinated successfully in 1995, demonstrating that the species is capable of seed-banking.

Elizabeth J. Farnsworth

01/01/2010

According to the U. S. Fish and Wildlife Service (1991, 1993), conservation and management of R. knieskernii involves integrated site protection and habitat manipulation to maintain early plant succession. Protection efforts focus on reducing known threats to plants, land acquisition, landowner agreements, and management of habitats to maintain conditions conducive to the species establishment and maintenance. 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).

Elizabeth J. Farnsworth

01/01/2010

Quantification of demography and reproduction, especially in small and marginal populations, to inform a systematic population viability analysis 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

Elizabeth J. Farnsworth

01/01/2010

Methods for ex situ cultivation appear to be relatively well-established for this taxon.