Flattened Oatgrass

mountain oatgrass
flattened oatgrass
slender oatgrass

Mountain oatgrass is a native, perennial bunchgrass. The culms are
slender, compressed, sometimes decumbent, and 12 to 32 inches (30-80 cm)
tall. The leaves are mostly at or near the base and up to 8 to 10
inches (20-25 cm) long. The inflorescence is a panicle; slender
branches bear two or three spikelets. The awn is bent and 0.2 to 0.3
inches (0.6-0.8 cm) long [4,10,12,20].

Mountain oatgrass occurs in the eastern United States and southeastern
Canada. It occurs from extreme southeastern Ontario east through
southern Quebec to Nova Scotia and south through New England and the
Appalachian Mountain region to northern Georgia. In the southeastern
United States, mountain oatgrass is restricted to the Appalachian
Mountains [10,12,20].

More info for the terms: fire regime, forest, low-severity fire

Mountain oatgrass occurs in oak (Quercus spp.) woods and grassy mountain
meadows which occasionally experience either lightning or human-caused
fire. Lightning commonly strikes the peaks and ridges of the southern
Appalachian Mountains from April through August [1]. Grassy balds in
the Pisgah National Forest of North Carolina respond favorably to fire,
becoming thick and lush. The low-severity fires burn very little of the
surface detritus [18]. Mountain oatgrass basal buds and dormant seeds
probably survive low-severity fire.

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: fire suppression, fuel

Prescribed fire is used to maintain grassy balds in the southern
Appalachian Mountains. Woody species are invading many grassy balds
because of fire suppression and decreased grazing [18]. Prescribed
burning was as effective as mowing in preventing woody species
establishment in Big Meadows, Shenandoah National Park, Virginia.
Biomass in the area prescribed burned in April was equal to the unburned
control by the end of the summer [7].

Grassy balds respond well to fall fires. The fuel is less compact and
favorable weather conditions last longer in the fall than in the spring
[18].

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More info for the term: hemicryptophyte

hemicryptophyte

In the southern Appalachians, mountain oatgrass is a frequent species on
grassy balds which occupy well-drained sites on ridges, broad slopes,
and dome-shaped summits between 5,000 and 6,000 feet (1,500-1,800 m) in
elevation. Grassy balds occur on slopes of all aspects but are most
commonly found on south, southwest, and west aspects. Mountain oatgrass
grows on dry sites but is susceptible to drought [19,26]. On wetter
areas of grassy balds, mountain oatgrass dominance gives way to sedges
(Carex spp.) [26].

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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):

FRES15 Oak - hickory

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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 term: forest

K100 Oak - hickory forest
K104 Appalachian oak forest

Fire probably kills the culms and leaves of mountain oatgrass.

Mountain oatgrass is not considered a regionally important forage
species [11,17], although it is an important pasture grass in the
Appalachian highlands [4,6].

More info for the terms: fern, forest, herbaceous

Mountain oatgrass occurs in forest openings, open woods, and mountain
meadows.

Mountain oatgrass is dominant in grassy balds of the southern
Appalachian Mountains. Other herbaceous plants occurring in grassy
balds include redtop (Agrostis alba), timothy (Phleum pratense), Canada
bluegrass (Poa compressa), Kentucky bluegrass (P. pratense), red fescue
(Festuca rubra), five-fingers (Potentilla canadensis), and sheep sorrel
(Rumex acetosella) [4,18,26,27]

On the Allegheny Plateau in Pennsylvania, deciduous forests which failed
to regenerate after logging support a dense groundcover of mountain
oatgrass, rough goldenrod (Solidago rugosa), tall flat-topped white
aster (Aster umbellatus), and bracken fern (Pteridium aquilinum) [13].

Mountain oatgrass is listed as a dominant species in the following
publication:

Vegetation of the Great Smoky Mountains [27]

More info for the term: graminoid

Graminoid

More info for the term: tree

The dense growth habit and competitive nature of mountain oatgrass
restricts tree seedling establishment [26]. Where tree establishment is
desired, herbicides easily control existing mountain oatgrass.
Glyphosate does not impede germination of residual dormant seeds, but
Bromacil delays germination for more than 1 year [13].

Mountain oatgrass is host to the systemic parasitic fungus Atkinsonella
hypoxylon [6].

CT DE GA KY ME MD MA NH NJ NY
NC OH PA RI SC TN VT VA WV NB
NS ON PQ

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Mountain oatgrass generally flowers from June to August [20]. In North
Carolina, mountain oatgrass flowers from mid-June to early July [4].

More info for the term: litter

Dormant seeds in the soil or litter germinate after fire. Mountain
oatgrass seedlings began growing 1 week after a spring fire on Gregory
Bald in the Great Smoky Mountains National Park [18]. Poverty grass, a
close relative of mountain oatgrass, regenerated from a seedbank after
fire on an upland site in Michigan [22].

More info for the terms: graminoid, ground residual colonizer, secondary colonizer

Tussock graminoid
Ground residual colonizer (on-site, initial community)
Secondary colonizer - off-site seed

More info for the terms: litter, seed

Mountain oatgrass reproduces by seed. Large amounts of seed are
produced annually, some of which remain dormant in the litter for at
least several years [13]. Mountain oatgrass also sprouts from
perennating buds at the base of the culms.

In two populations in North Carolina, mountain oatgrass produced an
average of 50 percent cleistogamous flowers [6].

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More info for the terms: cover, forest, herbaceous

Facultative Seral Species

Mountain oatgrass grows in full sun and in open woods. It does not
persist under closed canopies [4]. It establishes on disturbed sites
including recently logged and burned areas [14,18].

Grassy balds are persistent successional communities. The origin of
grassy balds is not fully understood, but former forests may have died
from ice storms, blow downs, fire, or climate change. Woody species
establishment is often delayed on these sites by dense herbaceous
cover, harsh environment, fire, and/or grazing [3,19].

Grassy balds in the Appalachian Mountains are succeeded by Rhododendron
spp. thickets, American green alder (Alnus viridis ssp. crispa)
thickets, or spruce (Picea spp.)-fir (Abies spp.) forests. A dense
carpet of moss (Polytrichum commune) advances into the grassy bald at
the edge of the spruce-fir forest and suppresses mountain oatgrass [5].

The currently accepted scientific name of mountain oatgrass is Danthonia
compressa Austin [10,12,20]. It is in the family Poaceae. There are no
currently accepted infrataxa. Mountain oatgrass may intergrade with
poverty grass (Danthonia spicata), a closely related species [4,12].

Danthonia compressa Aust. in Peck, Ann. Rep. N. Y. State Cab. 22:54. 1869.
Danthonia spicala var. compressa Wood, Bot. & Fl. ed. 1871. 396. 1871. (Based on D. compressa
Aust.) Danthonia Alleni Aust. Bull. Torrey Club 3; 21. 1872. (Rockaway, Long Island, Allen.) Danthonia Faxoni Aust. Bull. Torrey Club 6: 190. 1877. (White Mountains, New Hampshire,
Faxon in 1877.) Merathrepta compressa A. Heller, Muhlenbergia 5: 120. 1909. (Based on Danthonia compressa
Aust.) Pentameris compressa Nelson & Macbr. Bot. Gaz. 56: 469. 1913. (Based on Danthonia compressa
Aust.)
Culms compressed, rather loosely tufted, 40-80 cm. tall, erect or sometimes decumbent at the base or with short rhizomes; sheaths reddish above the nodes, glabrous or sparsely pubescent on the collar, with a conspicuous tuft of white hairs in the throat ; blades elongate, some of them commonly 20-25 cm. long, 2-3 mm. wide, usually flat, sometimes involute and subfiliform, scabrous; panicle 5-8 cm. (rarely up to 10 cm.) long, the slender branches bearing 2 or 3 spikelets, somewhat contracted after anthesis; glumes 10-14 mm., usually about 12 mm. long; lemmas 4—5 mm. long, sparsely villous nearly to the summit, the awned dorsal teeth 2-3 mm. long; terminal segment of the awn 5-6 mm. long; palea obtuse.
Type locality: Herkimer County, New York (Austin in 1868).
Distribution: Nova Scotia to Quebec, southward to Ohio and Virginia, and in the mountains to North Carolina and Tennessee.

Perennials, Terrestrial, not aquatic, Rhizomes present, 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 basal, below middle of stem, 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 hairy at summit, throat, or collar, Leaf sheath and blade differentiated, Leaf blades linear, Leaf blades very na rrow or filiform, less than 2 mm wide, Leaf blades 2-10 mm wide, Leaf blade margins folded, involute, or conduplicate, Leaf blades mostly glabrous, Leaf blades more or less hairy, Leaf blades scabrous, roughened, or wrinkled, Ligule present, Ligule a fringe of hairs, Inflorescence terminal, Inflorescence an open panicle, openly paniculate, branches spreading, Inflorescence a contracted panicle, narrowly paniculate, branches appressed or ascending, Inflorescence solitary, with 1 spike, fascicle, glomerule, head, or cluster per stem or culm, Flowers bisexual, Spikelets pedicellate, Spikelets laterally compressed, Spikelet 3-10 mm wide, Spikelets with 3-7 florets, Spikelets with 8-40 florets, Spikelets solitary at rachis nodes, Spikelets all alike and fertille, Spikelets bisexual, Inflorescence disarticulating between nodes or joints of rachis, rachis fragmenting, Spikelets disarticulating above the glumes, glumes persistent, Spikelets disarticulating beneath or between the fl orets, Rachilla or pedicel glabrous, Glumes present, empty bracts, Glumes 2 clearly present, Glumes equal or subequal, Glumes equal to or longer than adjacent lemma, Glumes 4-7 nerved, Lemma coriaceous, firmer or thicker in texture than the glumes, Lemma 5-7 nerved, Lemma 8-15 nerved, Lemma body or surface hairy, Lemma apex dentate, 2-fid, Lemma distinctly awned, more than 2-3 mm, Lemma with 3 awns, Lemma awn less than 1 cm long, Lemma awned from tip, Lemma awn from sinus of bifid apex, Lemma awn twisted, spirally coiled at base, like a corkscrew, Lemma awn once geniculate, bent once, Lemma margins thin, lying flat, Lemma straight, Palea present, well developed, Palea about equal to lemma, Palea 2 nerved or 2 keeled, Palea keels winged, scabrous, or ciliate, Stamens 3, Styles 2-fid, deeply 2-branched, Stigmas 2, Fruit - caryopsis, Caryopsis ellipsoid, longitudinally grooved, hilum long-linear.

Danthonia compressa is a species of grass known by the common names mountain oatgrass, flattened oatgrass, and slender oatgrass.