BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Aristida stricta | Pineland Threeawn 



GENERAL BOTANICAL CHARACTERISTICS : 
Pineland threeawn is a native, densely tufted, cool-season, perennial
bunchgrass.  It grows in large clumps that are up to 6 inches (15 cm)
across at the base.  Hundreds of stiff but flexible leaves arise from
each clump.  The narrow leaves are strongly inrolled, resembling a fine
wire, and may attain lengths of 20 inches (0.5 m) [8].  Most leaves die
within 1 year of their formation but are persistant; thus plants contain
much dead material [31].  Seedstalks are rare and occur only after fire.
They are about 3 feet (1 m) tall, erect, with a spikelike terminal
panicle about 12 inches (30 cm) long [14].

Plants produce tillers with no rhizomes, except for populations in south
Florida, which are rhizomatous [31].  Pineland threeawn is extremely
shallow-rooted and is easily pulled or dug from the ground.  Most roots
are within 8 inches (20 cm) of the soil surface, and no roots grow
deeper than 18 inches (46 cm) [31].


RAUNKIAER LIFE FORM : 
   Geophyte


REGENERATION PROCESSES : 
Pineland threeawn sexual reproduction is extremely rare.  Plants flower
in the summer or fall only if defoliation (i.e., fire, grazing, mowing)
has occurred within the previous 9 months.  Season and type of
defoliation greatly affect flowering vigor.  In general, late spring or
summer burning results in the most vigorous flowering, and sometimes
abundant seed production [5,31].  Plants may flower following fire at
other times of the year, but seeds are rarely formed.

Seedling establishment is poor.  Because of high optimum germination
temperatures (85-95 degrees Fahrenheit [30-35 deg C]) and after-ripening
requirements, germination cannot begin until the growing season after
dispersal [8,31].  In the long interum between dispersal and
germination, seeds are susceptible to destruction by fungi and seed
predators, resulting in scant natural germination [8].  In the
laboratory, germination has varied greatly from 2 to 97 percent [31],
and 20 to 25 percent [36].

Vegetative regeneration: Following disturbance which removes top-growth,
pineland threeawn initiates new growth from underground meristems [8].
Vegetative expansion is slow and complicated.  As the central portion of
older and larger clumps die, the clump becomes doughnut-shaped.  As the
clump expands the doughnut-shaped clump fragments, forming many small
clumps, each of which have the potential to expand and form a doughnut
of their own [8].


SITE CHARACTERISTICS : 
Pineland threeawn is the principal grass of longleaf and slash pine
savannas and flatwoods [8,31].  It also grows on dry sandhills in
association with turkey oak (Quercus laevis), in scrubby flatwoods and
dry prairies, and in seasonally wet grass-sedge bogs, where it grows on
elevated tussocks [2,8].

Soils and soil moisture:  Most pineland threeawn habitats are
characterized by relatively infertile sands and sandy loams [8].  The
soils of longleaf pine-pineland threeawn savannas are often psammaquods
or sandy ground water podzols [5].  These soils are typically composed
of over 90 percent fine sand with the water table ranging between 20 and
40 inches (50-100 cm) below the soil surface [5].  Pineland threeawn
tolerates seasonal flooding, but does not survive on sites where the
water table is within 2 inches (5 cm) of the soil surface year-round
[8].


SUCCESSIONAL STATUS : 
Facultative Seral Species

Pineland threeawn dominates fire-maintained southeastern grasslands and
savannas.  These communities are probably best described successionally
as "fire-maintained sub-climax or climax" [31].  In the absence of
frequent fire, hardwood trees and shrubs, especially saw palmetto and
gallberry, quickly invade and dominate savanna understories.  At the
Tall Timbers Research Station in Florida, hardwoods begin to dominate
savanna understories after just 4 to 8 years of fire exclusion [7].
Pineland threeawn is somewhat shade tolerant.  It can persist in the
shade of invading hardwoods for 20 to 40 years, but is eliminated if
fire does not occur after that time [8].


SEASONAL DEVELOPMENT : 
Growth begins in January in south Florida, and in March in Georgia.
Leaf blades grow 6 to 8 inches (15-20 cm) in 4 weeks [22].  Flowering in
Florida typically occurs from July through September [31], and from
September through November in the Carolinas [33].

Related categories for Species: Aristida stricta | Pineland Threeawn