Knieskern's Beaked-rush

Rhynchospora knieskernii

Description

Knieskern's beaked-rush is a plant of the sedge family endemic to the Pinelands region of New Jersey. The genus name Rhynchospora is from the Greek rhynchos, meaning beak, and spora, meaning seed, which refers to the beaked seed or fruit that is characteristic of the genus. This grasslike plant was generally considered to be an annual species (i.e., living for only one season); however, it is currently suspected to be a short-lived perennial in locations where habitat conditions are stable enough to allow uninterrupted growth year after year. Knieskern's beaked-rush grows from 0.6-24 in (1.5-61 cm), has slender culms branching from the base, and short, narrowly linear leaves. Small flower clusters are numerous and occur at distant intervals along the entire length of the culm. The fruit is obovate, narrow at the base, 0.04-0.05 in (1-1.3 mm), and equal in length to the six downwardly barbed (or rarely, upwardly-barbed) attached bristles. A tubercle (beak), which is the persistent base of the slender stalk containing the pollen tube on top of the achene, is about one-half the length of the achene.

Knieskern's beaked-rush is a wetland plant that occurs in groundwater-influenced, constantly fluctuating, successional habitats. An early-successional species and colonizer, this species is intolerant of competition, especially from woody species. It is found on naturally occurring, early-successional habitats and disturbed habitats such as burns, gravel and clay pits, road cuts, mowed roadsides, utility and railroad rights-of-way, cleared home sites, eroded areas, cleared edges of Atlantic white-cedar swamps, wheel ruts, and muddy swales. Periodic disturbance—either natural or human-induced—helps maintain a damp-to-wet site in an early ecological successional stage. This condition may be necessary for the successful colonization, establishment, recruitment, and maintenance of this species. Although not all plants produce culms each year, flowering and seed production have been observed in very young plants. Fruiting typically occurs from July to September. Seed dispersal mechanisms are not documented; however, bristles located on the achenes could assist in animal dispersal.

Habitat

The habitat originally thought to be required for the species is associated with bog iron deposits, which generally occur adjacent to slow-moving streams in the New Jersey Pinelands region. The formation of bog iron deposits is a product of the chemical action of slow-moving acid stream waters mixing with the iron-laden soils of stream beds. Soluble iron, which is oxidized by the aerated water and oxidizing bacteria, precipitates as red flocculent and sludge. This precipitate settles out of the moving water and is deposited in stream beds and adjacent wetland bogs, mixing with sand, mud, and decayed vegetation while continuing to harden into thick, rocky ironstone ore beds. Bog iron deposits are subject to the erosional forces of the stream system. The durability of the bog iron allows the habitat to remain essentially unchanged in an early ecological successional stage. Bog iron sites are considered a naturally maintained and long-lasting habitat for the species.

In the past, fire may have played an important role in creating and maintaining suitable habitat for Knieskern's beaked-rush. Occurrence records for Knieskern's beaked-rush indicate that this plant is found in wet open areas within fire-dependent, open pitch-pine forests. Fire suppression during the 1900s has changed the floral composition of the New Jersey Pinelands region and may have altered or eliminated a component of the ecosystem that naturally maintained habitat for this species.

Recent records on Knieskern's beaked-rush document that this species occurs in early-successional wet habitats created by human disturbances. These sites include: the edges of abandoned clay, sand, and gravel pits; borrow pits that are functioning as vernal ponds; ditches; unimproved roads; and railroad and powerline rights-of-way. Human-disturbed sites exhibit some of the same characteristics as bog iron sites, including a high water table, temporary inundation, and open, early-successional habitat with relatively bare substrate. In general, most of these sites require periodic human-induced disturbance to maintain their early-successional character. Plant species associated with Knieskern's beaked-rush include warty panic-grass, poverty-grass, and spatulate-leaved sundew.

Distribution

Knieskern's beaked-rush has always been considered rare. Currently, the species is only known to occur in New Jersey. Historically, two documented occurrences were found in Sussex County, Delaware. The Delaware Natural Heritage Program has been conducting yearly surveys for Knieskern's beaked-rush since the mid-1980s without finding a single new occurrence. The total number of documented occurrences in New Jersey is 52, which includes 14 historical and 38 extant populations. Six of the extant populations occur on sites that are considered to be naturally maintained in an early-successional vegetative stage and, therefore, should not require active management. The remaining 32 known extant populations occur on early-successional sites created as a result of sand, clay, and gravel mining; borrow pit excavation; cranberry bog construction; and road, powerline, and ditch construction through wetland areas. Of the 32 extant populations occurring on human-disturbed sites, three are on federal property, four are on state property, and 25 are on private property or rights-of-way.

Threats

Originally, the primary threat to the species was the loss of wetlands to urban and agricultural development. However, current state and federal wet-land protection laws have reduced the loss of wet-lands over time. Presently, vegetative succession is a major factor threatening Knieskern's beaked-rush; 19 of the 38 extant populations are currently undergoing vegetative succession that could eliminate them altogether. Without periodic intervention to reverse successional trends, these 19 sites will most likely become unsuitable for the species in the future. Human-induced threats to the species include alteration to wetland hydrology, off-road vehicle usage, trash dumping, and possibly roadside grading.

Apparently, fire can be both beneficial and detrimental to the species, depending on the timing, duration, and intensity of the burn.

Conservation and Recovery

The primary recovery goal for Knieskern's beaked-rush is the permanent habitat protection of existing sites. Habitats can be protected by developing management strategies for both public and privately owned Knieskern's beaked-rush sites and by securing commitments from land management agencies for long-term monitoring of the species. Further recovery objectives are to determine the capacity of the species to colonize new sites and establish populations. Continuing research on the species' life history, population viability, and specific habitat requirements is also essential to the species' recovery.

The New Jersey Natural Heritage Program surveyed historical sites and new sites for Knieskern's beaked-rush in 1984-85 using a soil/habitat predictive method. This method consisted of searching sparsely vegetated, open seepage areas of sandy loam or clay on soil types known to support other occurrences of the species. Several additional populations were discovered during these surveys.

In 1991 W. E. Brumback of the New England Wild Flower Society, Garden in the Woods, began germination tests on seeds collected by D. B. Snyder of the New Jersey Natural Heritage Program. Seeds that were placed in a seed bank in December 1991 germinated after being removed from the bank and sowed in February 1995, demonstrating that Knieskern's beaked-rush can be seedbanked successfully. Brumback also found that Knieskern's beaked-rush has a perennial nature when plants bloomed in two consecutive growing seasons during 1992-93.

Contacts

U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
300 Westgate Center Dr.
Hadley, Massachusetts, 01035-9589
Telephone: (413) 253-8200
Fax: (413) 253-8308
http://northeast.fws.gov/

New Jersey Ecological Services Field Office
927 North Main Street, Building D-1
Pleasantville, New Jersey 08232-1454
Telephone: (609) 646-9310
Fax: (609) 646-0352

References

Boyd, H. P. 1991. A Field Guide to the Pine Barrens of New Jersey. Plexus Publishing, Inc., Medford, New Jersey. 423 pp.

Gordon, T. 1993. "Monitoring and Survey of Rhynchospora knieskernii in New Jersey—1992." New Jersey Office of Natural Lands Management, Trenton, New Jersey. 9 pp.

U. S. Fish and Wildlife Service. 1993. Knieskern's Beaked-Rush (Rhynchospora knieskernii ) Recovery Plan. Hadley, Massachusetts. 40 pp.