(lesser blackscale sedge)
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Carex atrosquama is a tall, stout sedge with prominent black flowering head that occurs primarily in floodplains and meadows in the subalpine zone north of the Alaska Range crest in Denali. This species has a single stem bearing a terminal cluster of
spikes. Plants are tufted, growing 20-80 cm tall from a short
rhizome. The leaves are 2-5 mm wide, with reddish sheaths and are much shorter than the stem. The stem is scabrous. The
spikes (3-4) are erect, aggregated, and short-stalked, the
inflorescence 2.5-3 cm long. The lowest
bract is leaf-like and more or less equal in length to the
inflorescence. The terminal
spike is bisexual with the female flower above, male flowers below. Lateral
spikes contain only female flowers. The
pistillate scales are black,
lanceolate in shape and shorter than the
perigynia. The
perigynia are green (aging to brown), papillose, purple-beaked, and
elliptic in shape, 2.5-3.5 mm long. The fruits are
achenes, with 3
stigmas. Similar species in Denali include
C. media, in that species the
pistillate scales have a transparent margin, and the
spikes and
perigynia are smaller.
Carex atrosquama generally flowers around mid-summer in Denali.
C. atrosquama is
monoecious, but male and female flowers are produced in separate
spikes. Species in the genus
Carex are wind pollinated, but usually also self-pollinate to some degree (
Bertin 2007;
Friedman and Barrett 2009). Seeds are gravity and wind dispersed. It can also spread vegetatively through
rhizomatous growth.
Carex atrosquama occurs only in North America, where it is endemic to the western Cordillera, ranging from Alaska east to the Northwest Territories and south through British Columbia/Alberta into the Rocky Mountain states and Pacific Northwest. In Alaska, C. atrosquama occurs primarily in the mountains south of the Yukon River, with isolated stations to the north. In Denali, this species occurs most frequently in the northeastern quadrant of the park, but with stations in the mountains on both sides of the Alaska Range crest.
Details are shown in the Plots & Charts found at right, depicting recent Denali data.
In Denali, C. atrosquama is observed growing at elevations from 608 m to 1160 m with an average elevation of 844 m. This species is observed equally on north and south facing sites, but occurs over a wider range of elevations on south-facing slopes. It is found on sites that averaged 10 degrees in slope.
Details are shown in the Plots & Charts found at right. For more on how to interpret these figures, visit Understanding Data Presented.
C. atrosquama grows in alpine meadows, gravel bars, and lakeshores. Soil pH values for sites where C. atrosquama was observed ranged from 4.8 to 6.8 with an average value of 5.7.
Moist to well drained, somewhat dry sites.
