Arizona Cottontop

Arizona cottontop
cottontop
cotton-top
Arizona cottongrass
cotton grass
California cottontop

More info for the term: warm-season

Arizona cottontop is a native, perennial, long-lived, warm-season
bunchgrass [8]. It has slender, erect stems which are from 12 to 40
inches (30-100 cm) tall. The leaves are normally 3 to 5 inches (8-13
cm) long, but may be up to 10 inches (25 cm) in length. They are 0.125
to 0.25 inches (2-6 mm) broad [14,20]. The inflorescence is a narrow,
densely flowered panicle, usually 3 to 4.75 inches (8-12 cm) long [14].
Spikelets are normally borne in pairs on the rachis. The cottony
seedhead is covered with long silky hairs [24], and the seeds are about
0.07 inches (1.7 mm) long. Arizona cottontop's root system is finely
divided and branched. It is concentrated mostly in the upper 8 inches
(20 cm) of soil, but in coarse-textured soils it extend down to about 40
inches (100 cm) [8].

Arizona cottontop is distributed from the southwestern United States to
central Mexico [8,15,24]. It is also found in Baja California and is
reported from South America [19].

More info for the term: fire regime

Arizona cottontop is particularly tolerant of fire because the
growing points are just at or below the ground line [33].

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 terms: cover, fire suppression, forbs, fuel, grassland, litter, reclamation

In places where fire suppression has allowed invasion of original
semidesert grassland by woody plants, burning can reduce heavy brush
cover and suppress invasion. A maintenance fire should be a
dormant-season, relatively cool fire initiated under high relative
humidity and low wind speed. A reclamation fire should be hot, with low
relative humidity and relatively high wind speed to move fire across
fine fuels and into woody crowns. A first burn may not be uniform, but
with the release of Arizona cottontop and other grass species, fine fuel
will increase, and the second or third burn will be more uniform [33].

In southern Texas brushlands, mechanical roller chopping of brush
without fire led to increased production of forbs and sedges. With
burning after chopping, production shifted to predominantly perennial
grasses, including Arizona cottontop [33].

In western Texas, winter-spring precipitation was the key to successful
response of Arizona cottontop to fire. Species that accumulated the
most litter, including Arizona cottontop, benefited the most [40].

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More info for the term: hemicryptophyte

Hemicryptophyte

More info for the term: shrubs

Arizona cottontop is found on plains and hillsides on open,
well-drained sites [14,17]. Some of the diverse areas in which it
occurs include mesas and rocky hills in Arizona [24], deep hardland
range sites in Texas [5], and broad alluvial plains, fans, and river
bottoms in the Chihuahuan and Sonoran deserts [10].

Arizona cottontop grows on a wide variety of soils, including clayey loam,
sandy loam, and loose gravelly soils, as well as limestone ledges and
porphyritic hills. However, it is more abundant and productive on
clay, sand, or sandy-loam subsoils than on shallow, stony, or cobbly
soils [8].

In the low-fertility soils of some desert sites, Arizona cottontop
thrives under mesquite shrubs, where the nitrogen, sulfur, and
phosphorus availability is much higher. Cottontop shows evidence of
chlorosis and low fertility on some open desert sites [35].

Arizona cottontop has been recorded at the following elevations
[4,5,10,14,17,27,29,40]:

Area Elevation (feet) Elevation (m)

Arizona 1,000-6,000 305-1,830
Chihuahuan
and Sonoran
deserts 0-6,050 0-1,859
Colorado 5,500-5,800 1,675-1,770
Mexico 3,940-5,250 1,200-1,600
New Mexico 4,300 1,310
Texas 1,260-3,200 384-975

Within its geographical range, Arizona cottontop grows in a wide variety
of precipitation regimes, from areas of spring and summer maxima
separated by dry periods in Arizona, to high-summer, low-winter types in
Texas [8]. In much of its range, precipitation arrives during two
periods: with winter frontal systems during November to March and with
summer convection storms from June to September. However, across the
region annual precipitation and time of occurrence is extremely
variable, and extended drought is common.

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This species is known to occur in association with the following cover types (as classified by the Society of American Foresters):

66 Ashe juniper - redberry (Pinchot) juniper
67 Mohrs ("shin") oak
68 Mesquite
239 Pinyon - juniper
241 Western live oak
242 Mesquite

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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):

More info for the term: shrub

FRES30 Desert shrub
FRES31 Shinnery
FRES32 Texas savanna
FRES33 Southwestern shrubsteppe
FRES34 Chaparral - mountain shrub
FRES35 Pinyon - juniper
FRES38 Plains grasslands
FRES40 Desert grasslands

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

More info for the terms: cactus, shrub, woodland

K023 Juniper - pinyon woodland
K027 Mesquite bosque
K031 Oak - juniper woodlands
K039 Blackbrush
K040 Saltbush - greasewood
K041 Creosotebush
K042 Creosotebush - bursage
K043 Paloverde - cactus shrub
K044 Creosotebush - tarbush
K045 Ceniza shrub
K053 Grama - galleta steppe
K054 Grama - tobosa prairie
K057 Galleta - three-awn shrubsteppe
K058 Grama - tobosa shrubsteppe
K059 Trans-Pecos shrub savanna
K060 Mesquite savanna
K061 Mesquite - acacia savanna
K065 Grama - buffalograss
K071 Shinnery
K085 Mesquite - buffalograss
K086 Juniper - oak savanna
K087 Mesquite - oak savanna

Arizona cottontop is intermediate among semidesert grasses in its
susceptibility to damage from fire [7]. If a wet summer follows a fire,
cottontop will probably recover completely during the first growing
season. If the fire is followed by a dry summer, complete recovery will
probably require two summers [6,8].

Arizona cottontop responds quickly to spring and summer rains, grows
rapidly, and provides highly palatable green forage. The foliage cures
well, and some stems remain green in winter so that it is an important
winter feed [20]. It also makes rapid growth following winter rains,
and furnishes earlier forage than most associated grasses [15].

More info for the term: graminoid

Graminoid

More info for the terms: basal area, competition, cover, density, forbs, litter, series, shrubs

Arizona cottontop tolerates relatively heavy grazing over long periods.
Dormant-season grazing averaging over 65 percent use for periods up to
15 years had no apparent effect on longevity, changes in basal area, or
changes in plant height [8]. In studies of productivity, cottontop
succeeded about as well in dry as in wet years [28,30].

Arizona cottontop will thrive under most management strategies, provided
that the intensity of grazing is held to a reasonable level [8].
Grazing, particularly at the beginning of the growing season, actually
increases the sprouting and growth of axillary shoots, leading to
increased productivity [9]. However, because it is highly palatable
throughout the year, it is frequently overgrazed [20].

Two management practices are recommended to maintain optimum Arizona
cottontop productivity [8]:
1. If Arizona cottontop is dominant, utilization should be based on
50 percent use of cottontop. If it is not the dominant grass, its
use should average a little less than 60 percent.
2. Defer or reduce grazing by about 50 percent during the growing
season, 2 years out of 3. This will lessen the grazing impact on
Arizona cottontop, but still provide the stimulus for axillary
sprouting.

Under moderate grazing in Arizona, Arizona cottontop was somewhat more
dense under a year-long grazing schedule than under a rotation system,
but the difference was slight. These results were attributed to initial
plant densities near the maximum, and to moderate grazing. On range
that was initially in poor condition, rotation grazing improved
cottontop productivity [28]. Consistent heavy grazing during the summer
growing season adversely affects vigor and productivity of Arizona
cottontop [8].

An established stand of Arizona cottontop competes strongly with velvet
mesquite seedlings (Prosopis velutina) and deters the spread of velvet
mesquite into grasslands. However, in a mature stand of velvet mesquite
there can be great reduction of cottontop production. On many sites,
removal of velvet mesquite releases Arizona cottontop, with subsequent
large increases in cottontop production [8]. In Texas, when honey
mesquite (P. glandulosa var. glandulosa) was removed Arizona cottontop
increased most when the mesquite was cut at ground level and the stump
was painted with herbicide. Arizona cottontop remained consistently
above the control in its abundance with aerial spraying of honey
mesquite. However, it decreased or was completely replaced when
grubbing and chaining of honey mesquite induced a lower seral stage due
to soil disturbance [5,21]. Rootplowing produces a highly disturbed
seedbed, which reduces cottontop density and increases competition from
weeds [32].

In desert soils with very poor nutrient status, Arizona cottontop can be
much more productive under mesquite (Prosopis spp). However, under
these conditions cattle will preferentially graze Arizona cottontop
beneath the mesquite, which can result in scanty vegetational cover on
these sites. A manager might then conclude that mesquite is inhibiting
Arizona cottontop growth and should be eliminated, when the opposite may
be true [35]. Therefore, soil nutrient status should be assessed before
mesquite removal, and also before reseeding efforts. Deficiencies may
need to be corrected with commercial fertilizers [25].

Removal of the crown cover of redberry juniper (Juniperus pinchoti)
which had been killed by herbicide resulted in an increase in Arizona
cottontop on the site. However, cottontop was only found beneath the
dead junipers, and not between them [16].

In the Chihuahuan and Sonoran deserts a series of studies showed that
substantial increases in native forage production, including Arizona
cottontop, can be obtained if [10]:
1. Plant competition from shrubs and forbs is reduced (by
mechanical means or with herbicides)
2. Dead standing litter remains in place after treatment
3. Grazing is excluded or reduced.

AZ CA CO HI NV NM OK TX MEXICO

More info for the term: cover

Arizona cottontop provides good graze for livestock and fair graze for
wildlife [14].

Arizona cottontop was given a high palatability rating for cattle [2].
It is palatable throughout the year [14]. It is preferred by cattle
over most other grass species at all seasons of the year [8].

In a study of preferential grazing of native grasses and the introduced
grass species Lehmann lovegrass (Eragrostis lehmanniana) in Arizona,
cattle consumption of native grasses was greater than 75 percent, versus
less than 20 percent for Lehmann lovegrass. Arizona cottontop was a
preferred species even among the native grasses [29].

When compared to Arizona cottontop plants outside the canopy cover,
cattle grazed Arizona cottontop closely and preferentially under
mesquite. This may have been due to the greater palatability of those
plants because of their higher nutrient content [29].

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More info for the terms: culm, seed

Arizona cottontop is dormant during dry periods, but utilizes both
winter and summer precipitation. However, most herbage is produced
during the summer growing season [8]. It responds quickly to spring and
summer rains, making rapid growth [20], and also responds with rapid
growth following winter rains [15]. Essentially all basal culms
produced in any given year sprout during the spring growing period;
summer growth on most basal culms is a continuation of growth on shoots
that sprouted in spring [8]. Shoots are produced throughout the growing
season. Inflorescences begin emerging 2 to 3 weeks after growth starts
in the summer, and the topmost spikelets begin to fall within 5 to 8
days of full emergence. All seeds on a panicle have usually fallen
within 7 to 8 days of first shatter. New panicles are produced as late
in the fall as soil moisture is available [8]. Plants can set seed from
July to November when conditions are favorable [14]. Germinable seed is
therefore present whenever conditions are favorable for germination and
establishment.

Because Arizona cottontop has low-level apical dominance and a large
reservoir of buds at culm nodes, numerous axillary shoots develop over
the growing season. Removing the growing point at the beginning of the
summer growing season stimulates the sprouting and growth of axillary
shoots [8].

More info for the terms: fuel, litter, prescribed fire, seed, shrubs

Arizona cottontop survived a late March fire in light to moderate fuels
(1,000-4,000 pounds [454-1,816 kg] per acre of fine fuel) to provide
forage during a period of less than normal precipitation from May
through August in western Texas [18]. After a range fire in western
Texas, Arizona cottontop increased production for one to three growing
seasons after fire [37]. Also in western Texas, Arizona cottontop was
harmed by fire during dry years, but not during years when fire was
followed by favorable moisture [7].

In Texas, hot fires with 3,037 pounds fuel per acre [3,417 kg/ha] on
herbicide treated mixed brush released Arizona cottontop [39].

On an unburned site in southern Texas, low value forage species
predominated; perennial bunchgrasses were scattered and of low vigor.
By 3 to 5 years after a prescribed fire program, the site was dominated
by Arizona cottontop and other perennial bunchgrasses [33].

Wright [41] states that in shortgrass prairie with less than 13 to 15
inches (330-380 mm) of annual precipitation, grasses do not benefit
from burning, except when shrubs or litter have stagnated grass growth.

In the mixed-grass prairie of the Southern Great Plains, Arizona
cottontop was tolerant of fire, showing increased yield 1 year after
fire when moisture was adequate. Seed production was very prolific in
this species after being burned [40].

Tussock graminoid

More info for the term: seed

Arizona cottontop reproduces from seed, and can be either
self-pollinated or outcrossed. Over half of the florets of an Arizona
cottontop plant are self-pollinated. The self-pollinated ovaries can
mature to viable seed even if lack of soil moisture prevents the panicle
from emerging from the sheath [8]. Seeds drop from the branches at
maturity [20].

In a seed longevity test, Arizona cottontop seeds kept under
uncontrolled conditions maintained over 80 percent germination for 3
years, with declining germination of about 6 percent per year for the
next 14 years, to less than 10 percent [8]. In another study of seed in
uncontrolled storage, Arizona cottontop showed 25 percent germination
after 25 years [36].

Arizona cottontop reproduces vegetatively from basal buds, which sprout
primarily in the spring, producing the year's crop of basal culms, most
of which mature the following summer [8].

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This species can be found in the following regions of the western United States (according to the Bureau of Land Management classification of Physiographic Regions of the western United States):

7 Lower Basin and Range
11 Southern Rocky Mountains
12 Colorado Plateau
13 Rocky Mountain Piedmont
14 Great Plains

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More info for the terms: association, climax, grassland

Facultative Seral Species

Arizona cottontop is listed as an important member of the semidesert
grassland climax vegetation [8]. It is also a climax species in the
shortgrass community in Texas [2], and is listed as a dominant in the
mixed-prairie association in north-central Texas [5]. It is a climax
decreaser, becoming less abundant where rangelands are overgrazed
[11,30]. On some sites it becomes the dominant species when protected
from grazing, greatly surpassing other grasses in abundance [8].
Arizona cottontop is usually found interspersed with other grasses [20],
but in some wetter sites can form almost pure stands [8].

Trichachne californica (Benth.) Chase [15,23,38]

The currently accepted scientific name of Arizona cottontop is Digitaria
californica (Benth.) Henrard [15,23,38]. It is a member of the tribe
Paniceae in the grass family (Poaceae) [15]. There are no recognized
subspecies, varieties, or forms.

More info for the terms: forbs, seed, shrubs, warm-season

Arizona cottontop can be successfully reseeded on upland areas receiving
at least 11 inches (280 mm) of annual precipitation, provided a good
seedbed has been prepared. In New Mexico, Arizona cottontop gave the
best germination of all native forage plants tested, but seedlings made
slower growth than most other plants. Thus, moisture had to be
available for a longer period for Arizona cottontop seedlings. However,
once plants are established, they are drought hardy. Populations are
maintained by establishment of new plants from seed during wet years.
Once established, Arizona cottontop can be quite long lived. Some
plants live for more than 15 years, even when grazed [8].

In less favorable sites, reseeding efforts may not succeed. In the
Sonoran and Chihuahuan deserts extreme drought, overgrazing, sheet and
gully erosion, and plowing caused extreme deterioration of rangeland.
Native species, including Arizona cottontop, failed to persist after
reseeding efforts, and were replaced with introduced grasses, forbs, and
shrubs [10].

The accumulated heat needed for Arizona cottontop seeds to germinate is
on the low end for warm-season range grasses tested, and Arizona
cottontop is therefore one of the easier species to establish. It is a
good choice for native grass reseeding provided that the moisture
requirement for seedling establishment is met [22].

Valota saccharata (Buckl.) Chase, Proc. Biol. Soc
Wash. 19 : 188. 1906.
Panicum lachnanlhum Torr. Pacif. R. R. Rep. 7^ : 21. 1857. Not P. lachnanthum Hochst. 1855. Panicum saccharaium Buckl. Prel. Rep. Geol. & Agr. Surv. Tex. App. 2. 1866. Trichachne saccharata Nash, in Small, Fl. S:^. U. S. 83. 1903.
' p
Stems up to 8 dm. tall, tufted, smooth and glabrous; leaf-sheaths glabrous or hirsute; blades up to 1.5 dm. long, 3-5 mm. wide, linear-lanceolate, acuminate, glabrous or pubescent; panicle narrow, usually dense, up to 1.5 dm. long, its branches erect; spikelets 3-4 mm. long, exclusive of the long hairs which are commonly silvery-white, sometimes purplish, the first scale small or minute, the second scale lanceolate, as long as the fruiting scale and a little shorter than the third, 3-nerved, long-hairy, the third scale ovate-lanceolate to ovate, 5-nerved, acuminate, the fruiting scale brown when mature, lanceolate to ovate, acuminate, the tip white.
Type locality : Middle Texas,
Distribution : Colorado to Texas and northern Mexico.

Perennials, Terrestrial, not aquatic, Rhizomes present, Rhizome short and compact, stems close, Stems nodes swollen or brittle, Stems erect or ascending, Stems caespitose, tufted, or clustered , Stems terete, round in cross section, or polygonal, Stem internodes hollow, Stems with inflorescence less than 1 m tall, Stems, culms, or scapes exceeding basal leaves, Leaves mostly cauline, Leaves conspicuously 2-ranked, distichous, Leaves sheathing at base, Leaf sheath mostly open, or loose, Leaf sheath smooth, glabrous, Leaf sheath hairy, hispid or prickly, Leaf sheath and blade differentiated, Leaf blades linear, Leaf blades 2-10 mm wide, Leaf blades mostly flat, Leaf blades mostly glabrous, Ligule present, Ligule an unfringed eciliate membrane, Inflorescence terminal, Inflorescence solitary, with 1 spike, fascicle, glomerule, head, or cluster per stem or culm, Inflorescence a panicle with digitately arranged spicate branches, Inflorescence with 2-10 branches, Inflorescence branches 1-sided, Lower panicle branches whorled, Rachis angular, Flowers bisexual, Flowers unisexual, Spikelets pedicellate, Spikelets dorsally compressed or terete, Spikelet less than 3 mm wide, Spikelets with 1 fertile floret, Spikelets with 2 florets, Spikelet with 1 fertile floret and 1-2 sterile florets, Spikelets paired at rachis nodes, Spikelets all alike and fertille, Spikelets bisexual, Spikelets disarticulating below the glumes, Spikelets secund, in rows on one side of rachis, Rachilla or pedicel glabrous, Glumes present, empty bracts, Glumes 1 clearly present, the other greatly reduced or absent, Glumes 2 clearly present, Glumes distinctly unequal, Glumes equal to or longer than adjacent lemma, Glume equal to or longer than spikelet, Glume surface hairy, villous or pilose, Glumes 3 nerved, Glumes 4-7 nerved, Lemmas thin, chartaceous, hyaline, cartilaginous, or membranous, Lemma similar in texture to glumes, Lemma 5-7 nerved, Lemma apex acute or acuminate, Lemma awnless, Lemma margins thin, lying flat, Lemma straight, Palea present, well developed, Palea membranous, hyaline, Palea about equal to lemma, Stamens 3, Styles 2-fid, deeply 2-branched, Stigmas 2, Fruit - caryopsis, Caryopsis ellipsoid, longitudinally grooved, hilum long-linear.

Digitaria californica is a species of grass known by the common name Arizona cottontop. It is native to the Americas, where it can be found in the southwestern United States, Mexico, Central America, and South America.

This perennial grass forms a clump of stems reaching up to a meter in height. The branching root system can reach one meter deep. There are no rhizomes or stolons. The leaf sheaths around the stems can be very hairy to woolly. The leaves are usually short and narrow. The inflorescence is a dense, narrow panicle containing pairs of woolly-haired spikelets.

This plant grows in a number of habitat types, including desert scrub and shrublands, shrubsteppe, and savanna. In the desert it sometimes grows beneath mesquites where it thrives in the local nutrients. It tolerates varying precipitation amounts and survives easily in drought conditions, becoming dormant at times, then growing quickly when rain returns. Much of its growth occurs in the summer, after the spring and summer rain cycles.

This species is a preferred grass for livestock such as cattle. It tolerates high grazing activity, but not overgrazing.