Seaoats

sea oats

More info for the terms: caryopsis, fruit

Sea oats is a native, perennial, semitropical, rhizomatous C4 grass
[12,14]. Culms are stout and 3.3 to 6.6 feet (1-2 m) tall [2,4].
Leaves are both basal and cauline; leaf blades are up to 24 inches (60
cm) long. The inflorescence is a narrow condensed panicle 8 to 20
inches (20-50 cm) long [21]. Spikelets are very flat, 10- to
20-flowered, and 0.6 to 1.2 inches (1.5-3.0 cm) long [2,14]; they
disarticulate below the glumes and fall entire. The fruit is a
caryopsis [10]. Rhizomes are elongated and extensively creeping [2,14],
readily rooting at the nodes when buried by sand [4]. Sea oats develops
a dense concentration of surface roots as well as a penetrating system
of deep roots [12].

Sea oats occurs along the mainland coast and barrier islands from
Northampton County, Virginia, through Florida [14]. It continues west
along the Gulf coast through Texas and south to Tabasco, Mexico [11].
It is also widely distributed in the Bahama islands and occurs on some
sandy areas of the northwestern coast of Cuba [2,4,10,21].

More info for the term: fire regime

Sea oats reproduces vegetatively [14]. It probably sprouts from
rhizomes after aerial portions are burned.

FIRE REGIMES :
Find fire regime information for the plant communities in which this
species may occur by entering the species name in the FEIS home page under
"Find FIRE REGIMES".

More info for the term: cover

Recurring fires are common to the maritime strand of the Coastal Plain
of the southeastern United States [20].

Although blowouts, shifting sand, and wandering dunes are characteristic
of strands, these phenomena were much accelerated in the past by grazing
management practices. On some barrier islands sea oats and other dune
grasses were burned off to improve forage. This gave more palatable
forage for a brief part of the growing season, but it also reduced the
total cover and greatly accelerated the inland movement of sand. On
Smith's Island, North Carolina, what was formerly a barren area of
shifting small dunes has developed substantial cover because of reduced
grazing and elimination of fire [20].

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More info for the terms: geophyte, hemicryptophyte

Hemicryptophyte
Geophyte

More info for the term: forb

Sea oats is found on upper beaches, dunes, and loose sands near
seashores in the southeastern United States [2,4,10,14,15,21,29] but it
is seldom found in the forb zone of lower beaches [26]. Sea oats is one
of the most important grasses on dunes and continuous dune ridges [15]
because it helps build and maintain the sites on which it grows. Sea
oats is dominant on the ocean facing part of fore dunes, often dominant
at the top of the more stable second dune system, and much less
prominent in the depression between the two [1,15,16,23]. This reflects
the close zonal relationship of sea oats to the deposition of salt
spray. On Bogue Bank, North Carolina, sea oats was dominant where salt
spray was greatest. The highest salt concentration was on the windward
side of the fore dune; the crest of the rear dune had a somewhat lower
concentration, and the depression between the dune systems received much
less salt depostion [20].

Sea oats sites have in common exposure to wind, salt spray, storms,
drought [1], often deep and shifting sand, and occasional fires and salt
water inundation. These unstable habitats suffer wind and water
erosion. The soil has low water retaining ability and excellent
drainage. Evaporation rates are high due to constant air movement, high
temperatures, and full sunlight [20].

Sea oats is found on the Upper Keys of Florida, where sands are of coral
origin, and on the Lower Keys which are limestone and have carbonate
sands. The Atlantic seaboard beaches and dunes have siliceous sands.
Soils of the Gulf Coast islands are fine to medium sand, with almost no
organic content. On Cat Island, Texas, the organic content of the soil
in the sea oats zone was measured at 0.07 percent [20].

Soils on the Coastal Plain are strongly leached, rich in aluminum and
iron oxides, and usually deficient in many nutrients. However, salt
spray carries some essential micronutrients to beach and dune plants
[13,23].

Sea oats occurs on sands with the following reactions: Bogue Bank,
North Carolina, pH 7.4 to 7.9; Jupiter, Florida, pH 7.5; Cat Island,
Texas, pH 6.9 [3,20].

Climate in the maritime communities of the southeastern United States is
one of mild winters with high humidity and long, hot, humid summers.
The July mean temperature is about 81 degrees Fahrenheit (27 deg C). On
the Atlantic coast most rainfall occurs during summer and early fall.
Rainfall averages over 39 inches (1,000 mm) per year, and in some places
considerably more. In Florida, Miami receives 60 inches (1,524 mm) of
precipitation annually; Key West receives 38 inches (965 mm); Tortugas
receives 33 inches (838 mm). There is a steady decrease in rainfall
from Pensacola, Florida, west to Brownsville, Texas, where rainfall is
27 inches (680 mm) per year. October and November are the driest months
on the northern and eastern Gulf coast. March is the driest month at
Brownsville, Texas [19,20,23].

Soil temperature variation on sea oats sites is greatest in the surface
inch of soil. In the early afternoon soil surface temperatures of 125
to 127 degrees Fahrenheit (52-53 deg C) are common in the early
afternoon when air temperature is 95 to 100 degrees Fahrenheit (35-38
deg C) [20].

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This species is known to occur in the following ecosystem types (as named by the U.S. Forest Service in their Forest and Range Ecosystem [FRES] Type classification):

FRES16 Oak - gum - cypress
FRES41 Wet grasslands

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This species is known to occur in association with the following plant community types (as classified by Küchler 1964):

K078 Southern cordgrass prairie
K090 Live oak - sea oats

Sea oats culms are probably killed by fire.

More info for the term: marsh

Cattle graze sea oats [16].

Most sea oats spikelets falling on stable sites (and therefore not
rapidly buried by sand) are eaten by birds and mammals [16].

On the east coast of Florida, the oldfield mouse inhabits barrier island
dunes. It is found in open habitats of sea oats fore dunes and it feeds
on sea oats fruits [15]. On Perdido Key, Florida, ideal habitat for the
endangered Perdido Key beach mouse consists of well-developed dunes
vegetated with sea oats and other dune grasses. The Perdido Key beach
mouse lives in burrows constructed in the dunes. It feeds primarily on
seeds of beach herbs, including sea oats, and insects [7].

Marsh rabbits feed on sea oats in the dune areas of the barrier islands
of Georgia. Songbirds, especially song sparrows and other fringillids,
and red-winged blackbirds are the major consumers of sea oat seeds [16].

More info for the term: vine

Sea oats is listed as a dominant in the following published
classification:

Plant communities of Texas (Series level) [25]

Besides those listed in the Kuchler Plant Associations, common
associates of sea oats include beach purslane (Sesuvium portulacastrum),
goatfoot morning glory (Ipomaea pes-caprae), railroad vine (Ipomaea
stolonifer), sea rocket (Cakile edentula), evening primrose (Oenothera
humifusa), beach spurge (Chamaesyce bombensis), beach sunflower
(Helianthus debilis), seashore-elder (Iva imbricata), beach dropseed
(Sporobolus virginicus), beach berry (Saevola plumieri), and bay cedar
(Suriana maritima) [3,15,23,26].

More info for the term: graminoid

Graminoid

More info for the terms: cover, rhizome

Sea oats is an excellent dune builder and sand binder. It thrives in
areas where dune building is active [23] and contributes to maintenance
of the dune in its position. Sea oats traps windblown sand, forming
mounds of sand which increase as the plant responds with increased
growth [15]. It possesses an extensive root and rhizome system which
produces new growth following sand burial [4].

Sea oats is well adapted to and dominates the most exposed areas of the
dune where soil moisture is low. It tolerates drought, salt spray, and
rapid sand burial. Maximum leaf elongation occurs at 12.8 percent soil
moisture. Stomates close and leaf elongation slows when soil moisture
falls below 8.5 percent. Plants do not wilt until soil moisture falls
below 1.2 percent. Once drought is relieved, sea oats can recover from
very negative water potentials. Excessive soil moisture from a high
water table or inundation has a greater negative effect on sea oats
growth than does low soil moisture. With waterlogging stress due to a
high water table, stomates close and there is reduced biomass
production. Inundation of roots for just a few days results in death of
the plant [12].

Erosion of dunes is accelerated by grazing. When sand on the windward
slope is not anchored by sea oats and other vegetation it is carried
over the top by the wind and deposited on the lee side, resulting in
migrating or "marching" dunes. When overgrazing results in the loss of
dune vegetation and the subsequent loss of the stable dune system, a
wide, flat beachfront may develop. Then extremely high storm induced
tides may inundate the entire beachfront and erode the older,
well-established dune systems protecting the interior, as occurred on
Cumberland Island, Georgia in 1971. Grazing has transformed several of
the banks in North Carolina into barren islands of shifting sand. Dune
damage from grazing has also been reported from South Carolina, Texas,
and several islands along the Georgia coast [16]. Vegetation on North
Padre Island, Texas, is still recovering from cattle grazing from 1850
to 1971, when it was discontinued [1].

Sea oats is adversely affected when the dunes on which it grows are
altered by urban development, by the impact of off-road vehicles on
vegetation cover and compaction of soil, and by pollution of adjacent
waters by treated and untreated sewage, fertilization, and contaminants
from marinas, fish processing plants, and highways [23].

Sea oats was grown under greenhouse conditions in Louisiana dune sand.
Addition of the macronutrients nitrogen, phosphorus, and potassium
resulted in significantly greater leaf-elongation rates, number of
stems, and aboveground biomass than in controls with no additions.
However, additions of the micronutrients iron, manganese, copper, and
zinc in conjunction with the macronutrients led to reduced leaf
elongation and number of stems compared to controls. Micronutrients
alone had no positive or negative effects [13].

Sea oats seedlings were outplanted to Miami Beach, Florida, beaches to
enhance beach stability. When seedlings were inoculated with
vesicular-arbuscular (VAM) fungi there were increases in seedling growth
over those that were not inoculated. Root colonization by VAM fungi was
higher when the inoculum was already-colonized roots rather than spores
alone [28].

Sea oats has essentially no forage value for livestock [9].

AL FL GA LA MS NC SC TX VA MEXICO

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More info for the term: fruit

Sea oats growing season is May 1 to September 4 on Currituck Bank, North
Carolina. The germination period of sea oats seeds there is late May to
the middle of June [26].

Spikelets fall from the plant and disperse in late fall and early winter
[16].

Sea oats flowers and sets fruit (combined) at the following times:

Carolinas June-November [21]
Florida
central spring-fall [29]
panhandle October-November [2]
Texas April-November [18,9]
General range June-September [4]

More info for the terms: ground residual colonizer, herb, rhizome

Rhizomatous herb, rhizome in soil
Ground residual colonizer (on-site, initial community)
Initial-offsite colonizer (off-site, initial community)

More info for the terms: culm, seed, spikelet

Sea oats sprouts from rhizomes and from perennating buds at the bases of
culms [14]; growth and tillering is stimulated by sand burial [15], and
new shoots and roots arise from the nodes of both rhizomes and aerial
stems [5]. Sea oats also reproduces by seed [10].

Sea oats is wind pollinated. Florets open and close in the early
morning; they open only once. Cross-pollination may be required for sea
oats to produce an appreciable number of seeds. The very small sea oats
populations on the Louisiana coast west of the Mississippi Delta produce
average seed numbers of 0 to 9.53 per culm, depending on the population.
Seeds that are produced have high germination rates [11].

Sea oats shows a trend toward lower seed production with decreasing
latitude. Seeds from Bogue Bank, North Carolina, produced an average of
2.24 seeds per spikelet, which was about 30 percent of pollinated
ovaries; the remaining ovaries aborted. In southern Florida 0.6 seeds
per spikelet were found [11].

Sea oats spikelets are rapidly disseminated by wind, and are usually
soon buried where sand is accreting [6]. Wind, ocean currents, and
animals may disperse seeds to island and mainland beaches [3,15]. In
storms, seeds and plant parts can be carried great distances [20].

The cold treatment required to break seed dormancy decreases southward
along the range of sea oats, and is nonexistent for the south Atlantic
coast Florida populations. Seeds from North Carolina gave optimal
germination when cold-layered moist for 30 days at 40 degrees Fahrenheit
(4.4 deg C) before being given an alternating thermoperiod (conditions
of no light and alternating temperatures of 65 degrees Fahrenheit [18.3
deg C] for 17 hours followed by 95 degrees Fahrenheit [35 deg C] for 7
hours). No cold and/or moist treatment was required for seeds from
Louisiana; room temperature treatment gave highest germination, but
moist cold (40 degrees Fahrenheit [4.4 deg C]) pretreatment gave rates
almost as high. Exposure of seeds to 30 days of dry cold at 40 degrees
Fahrenheit (4.4 deg C) adversely affected germination. Louisiana seeds
collected October 1981 and tested in April 1982 had germination rates of
78.0 to 88.8 percent under the alternating thermoperiod described above
[11].

Seedlings establish during the first growing season and produce
extensive tillers by the second season [16].

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More info for the terms: climax, forest, hardwood, seed, succession

Facultative Seral Species

Sea oats is a pioneer species [15]. It spreads locally through
vegetative reproduction; it colonizes new areas primarily through seed
dispersal [11], but sea oats plant parts can also be dispersed by ocean
currents. Of 17 surveyed small islands near Key West, Florida, sea oats
had colonized 14 [15].

Sea oats is also a climax species because of its high tolerance for salt
spray. Succession in the salt spray community is limited primarily by
the intensity of the spray, and does not show the usual climatically
controlled pattern [20]. Sea oats is dominant on ocean-facing primary
dunes even if the dunes are stable because it tolerates more salt spray
than other species. If the shoreline is rising, however, the beach in
front of the primary dunes may accrete and new dunes form in front of
old ones. Then distance from the ocean to the original dunes will
increase, the effect of salt spray will diminish [23], and sea oats may
be replaced by other vegetation [16]. Eventually, succession to a
climax forest of subtropical mixed hardwood may occur [23].

Rather than rising, most of the shoreline of the southeastern United
States is subsiding. On the Gulf coast west of the Mississippi Delta to
Texas, the rate of coastal retreat is 3.3 to 164 feet (1-50 m) per year.
Sea oats can achieve vegetative lateral spread of 2 to 6 feet (0.6-1.8
m) per year, but this is generally not sufficient to keep pace with the
high rate of subsidence. Sea oats is not dominant in this area and is
reduced to a few sparse, scattered populations [11].

The currently accepted scientific name of sea oats is Uniola paniculata
L. [10,14,29]. It is in the family Poaceae. There are no currently
accepted infrataxa.

Sea oats was used in experimental dune building and vegetative
stabilization on Timbalier Island, Louisiana, a barrier island which is
sand-deficient. Sand fencing was used to stimulate sand accretion on a
washover terrace breached in 1979 during a storm surge. Fencing and
vegetation planting was begun May 1981, and the site was fertilized in
late September 1981. Sea oats was planted in November 1981, between
already planted bitter panicum (Panicum amarum). Sea oats had a 25
percent survival rate in May 1982, and a 23 percent survival rate by
August 1982. Sand accumulation on the sand-fenced and vegetated areas
was substantial over a 3-year period (1981-1984). Without sand fencing
vegetation did not cause appreciable vertical accretion of sand [19].

Sea oats is used in Florida to enhance beach stability when lost sand is
replaced. Replacement sand is shaped and then planted with sea oats and
other pioneer species to begin the dune-building process [28].