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Rhynchospora
knieskernii
Photo by Renee Scagnelli
NJ Botany
Rhynchospora knieskernii (Knieskern's
beaked rush)
KNIESKERN’S
BEAKED-RUSH
Rhynchospora
knieskernii
J. Carey
TAXONOMY
Due
to its limited distribution and its early discovery in 1843 in Ocean
County, New Jersey,
there are no valid synonyms for this taxon. Peter D. Kneiskern, M.D. discovered the
species and labeled it as Rhynchospora
grayana,
which is not a valid name. John
Carey published the name R. knieskernii in 1847.
NJ
NATURAL HERITAGE PROGRAM
This
species is listed as threatened pursuant to the ESA of 1973. It is also listed in G1,
S1, Listed Protected in
the Pinelands and Endangered in the State of New
Jersey.
The total number of documented occurrences is
48, which include 14 historical (12 in NJ and 2 in Del.)
and 34 extant populations (all in NJ).
It is known from Atlantic,
Burlington,
Camden,
Monmouth, and Ocean counties in NJ.
DESCRIPTION
OF PLANT
New
Jersey has 17 species of Rhynchospora
and there are approximately 200. Most
of the North American species are confined to the Atlantic coastal
plain from Mass. Southward. Knieskern’s
beaked-rush has been considered to be an annual; however, recent
information suggests that the plant may be a perennial or
semi-perennial. It
grows from 1.5 to 60 cm high (0.6 to 24 inches), has slender culms
branching from the base, and short, narrowly linear leaves. Small spikelets are numerous and occur
at distant intervals along the entire length of the culm.
The achene
is obovate, narrow at
the base, 1.1 to 1.3 millimeters long, and equal in length to the six
downwardly-barbed, or rarely, upwardly-barbed attached bristles. A tubercle, which is the
persistent base of the two-cleft style on top of the achene, is about one-half the
length of the achene.
HABITAT
It
is an obligate hydrophyte
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 generally found on relatively bare substrates with sparse vegetation
and limited duff. The
substrates the species is found on are continually moist to wet, and
are described as various combinations of sand, clay, bog ore, gravel,
and peat. Periodic
disturbance, either natural or human-induced, which maintains a
damp-to-wet site in an early seral
stage may be
necessary for the successful colonization, establishment, recuitment and maintenance of Knieskern’s
beaked-rush. Associated
species include:
Amphicarpum
purshii Kunth
Blue Maiden-Cane
Andropogon
glomeratus (Walt.)
B.S.P. Bushy
Bluestem
Aristida
longispica Poir.
Red Three-Awn
Bartonia
virginica (L.)
B.S.P. Yellow Screwstem
Comptonia
peregrina (L.)
Coult. Sweet-Fern
Drosera
filiformis Raf.
Thread-Leaf Sundew
Drosera
intermedia Hayne
Spoon-Leaf Sundew
Eleocharis
microcarpa Torr.
Small-Fruit Spike-Rush
Eleocharis
olivacea Torr.
Bright-Green Spike-Rush
Eleocharis
tuberculosa (Michx.) Roemer
& J.A. Schultes Cone-Cup
Spike-Rush Euthamia caroliniana
(L.) Greene ex Porter & Britt. Slender Goldentop
Gentiana
autumnalis L. Pine-Barren Gentian
Hypericum
canadense L. Lesser Canadian St.
John’s-Wort
Hypericum
gentianoides
(L.) B.S.P.
Orange-Grass
Lobelia
nuttallii J.A.
Schultes Nuttall’s
Lobelia
Lyonia
mariana (L.)
D. Don Piedmont
Staggerbush
Panicum
rigidulum
var. pubescens (Vasey)
Lelong Red
top Panic Grass
Panicum
verrucosum Muhl.
Warty Panic Grass
Panicum
virgatum L. Wand Panic Grass
Polygala
nuttallii Torr. & Gray Nuttall’s
Milkwort
Polygala
cruciata L. Drumheads
Rhexia
virginica L. Handsome-Harry
Rhynchospora
alba (L.) Vahl White Beak Sedge
Rhynchospora
capitellata (Michx.) Vahl Brownish Beak Sedge
Rhynchospora
gracilenta Gray Slender Beak Sedge
Schizachyrium
scoparium (Michx.) Nash
Little False Bluestem
Vaccinium
macrocarpon Ait.
Large Cranberry
Viola
lanceolata L. Bog White Violet
Viola
×primulifolia L.
(pro sp.) [lanceolata × macloskeyi]
Primrose leaved violet
Xyris
difformis Chapman Bog Yellow-Eyed-Grass
BIOLOGY/ECOLOGY
This
species in New Jersey
fruits from July to September. Seed
dispersal mechanisms are not documented.
However, bristles on the achenes could assist in animal
dispersal. Note: I
have had many Rhynchospora
achenes
hanging on my pants after fieldwork.
Information
is lacking on reproductive biology, seed bank longevity and viability,
seed dormancy mechanisms, conditions necessary for germination and
seedling establishment and level and distribution of genetic
variability for this species.
POPULATION
QUALITY
Population sizes have
been reported in areal
cover by square yards and by roughly estimating the number of
individuals at a site. According
to cursory estimates, the extant populations vary in size of areal cover from one square yard
to approximately 150 square yards.
THREATS
R.
knieskernii
populations occur in early-successional,
human-disturbed environments. Any
vegetative succession will make these sites unsuitable.
Any altering of site hydrology or even natural
events such as drought,
could eliminate site suitability.
Fire can be beneficial to the establishment of
populations or detrimental to the maintenance of it depending on the
timing, duration and intensity of the burn.
While some disturbance is necessary to
maintain R. knieskernii
on a site, off-road vehicles, trash dumping and roadside grading can
cause local extirpation of this species.
MONITORING
Like
many rare plants in New Jersey,
we do not know enough about their ecology, life history, etc. We need to know that the
early-successional stage
is necessary as well as the species being an obligate wetland species. Known sites should be
monitored each year or two. New
searches where habitat exists should be done as well as searches in
historic sites. New
site are being found for this species.
MANAGEMENT
Active
management is needed to protect wetland habitats and maintain them in
an early successional
stage. Active
management is also needed for populations of this species along edges
of streams which represents naturally-disturbed habitats..
Note:
Most of this information was taken from the KNIESKERN’S
BEAKED-RUSH RECOVERY PLAN from the U.S. Fish and Wildlife Service,
Region Five, Hadley,
Massachusetts
that is available on the internet at
http://ecos.fws.gov/docs/recovery_plans/1993/930929b.pdf
Bill
Olson
Botanical Consultant
1005 Lakewood
Farmingdale Road
Howell, New
Jersey 07731
732 961 1946
wolson3@optonline.com
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