Hairy Orcutt Grass

Orcuttia pilosa

Description

Orcuttia pilosa (hairy orcutt grass) was collected in 1938 from a single locality in eastern Stanislaus County, California, at the time these specimens were considered to be a more robust form of O. tenuis. The species was described O. pilosa three years later after examining additional collections from Merced and Madera counties in San Joaquin Valley.

O. pilosa is a densely tufted, usually densely pi-lose, annual reaching about 2-8 in (5.1-20.3 cm) in height. The stems are erect or decumbent at the base. The inflorescence is spikelike and rather elongate, with the spikelets remote on the axis below and usually strongly congested above. The equal-length lemmas are deeply cleft into fine teeth that are sharp-pointed or short-awned. O. pilosa and O. tenuis grow together over a portion of their respective ranges but are readily distinguished, as the stems of O. pilosa are simple, sprout freely from the base, and never branch from the upper nodes. Additionally, the spikelets of O. pilosa are strongly congested at the apex of the inflorescence, and the stems and leaves are larger.

Habitat

O. pilosa grows in the basins and margins of vernal pools of the Central Valley of California.

Distribution

O. pilosa occurs along a 223-mi (359-km) stretch on the eastern margin of the San Joaquin and Sacramento valleys extending from Tehama County south through Merced and Madera counties to Stanislaus County. Previously known from 34 populations, by the late 1990s about 25 O. pilosa populations (24 native and 1 introduced) existed, the balance having been variously extirpated by agricultural land conversion, urbanization, and intensive cattle grazing over its four-county range.

Only 12 of these extant populations are considered stable. Twenty of the O. pilosa populations are on private land; just five are on public land. The private land locations consist of a single population in Butte County, four in Stanislaus County, six in Madera County, and nine in Tehama County. Four of the nine populations in Tehama County are located on the Nature Conservancy's (TNC's) Vina Plains Preserve; however, only one of the preserve sites is excluded from an agreement allowing cattle grazing. The locations on public land consist of three ungrazed populations on the Sacramento National Wildlife Refuge, one population on U.S. Bureau of Reclamation (BOR) lands, and a translocated population on land owned by the California State Department of Transportation.

Threats

The chief threat to O. pilosa is habitat alteration and destruction through urban development and agricultural land conversion. Nine populations of O. pilosa have been lost and two others are possibly extirpated. Fourteen of the remaining 25 native extant populations of this plant are variously threatened by urbanization, agricultural land conversion, competition from non-native weeds, a highway expansion project, and off-highway vehicle use.

Urbanization has extirpated three populations ofO. pilosa in Madera County. The 200-acre (81-hectare) Merced County Landfill will destroy vernal pools contained in its project area, some of which contain O. pilosa. One population of this plant in Madera County is threatened by proposed expansion of State Highway 41.

Conversion of land to agricultural use since the 1980s is known to have eliminated five populations of O. pilosa in Stanislaus County, two in Madera County, and one in Merced County. Agricultural land conversion threatens eight more populations of O. pilosa in Madera and Stanislaus counties. Five of the 12 remaining populations of this taxon in Madera, Merced, and Stanislaus counties have been damaged by discing (plowing) or discing combined with grazing.

The non-native grasses L. multiflorum, H. geniculatum, and P. monospeliensis, along with the alien perennial Sida hederacea, threaten two populations of O. pilosa in Tehama County and one in Stanislaus County. The primary threat to populations of this taxon on TNC's Vina Plains Preserve is competition from aggressive alien weeds, including Convolvulus arvensis, Proboscidea louisianica, and Xanthium strumarium.

Off-highway vehicle damage has been reported to one population of O. pilosa in Madera County.

Conservation and Recovery

Existing conservation easements do not adequately protect this plant.

Contact

U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
Eastside Federal Complex
911 N.E. 11th Ave.
Portland, Oregon 97232-4181
Telephone: (503) 231-6121
http://pacific.fws.gov/

Reference

U.S. Fish and Wildlife Service. 26 March 1997. "Determination of Endangered Status for Three Plants and Threatened Status for Five Plants from Vernal Pools in the Central Valley of California." Federal Register 62 (58): 14338-14352.