Slender Orcutt Grass

Orcuttia tenuis

Description

Alice Eastwood first collected Orcuttia tenuis (slender orcutt grass) in 1912 in Shasta County. These specimens were considered to be O. californica prior to Hitchcock's 1934 description of O. tenuis as a new species, based upon spikelet arrangement as well as lemma tooth morphology. Slender Orcutt grass, Orcuttia tenuisis, is a weakly-tufted and sparsely-pilose annual grass. It grows about 2-6 in (5-15 cm) in height, producing one to several erect stems that often branch from the upper nodes. The inflorescence of this plant is elongate, with the spikelets usually remote along the axis and slightly, if at all, congested toward the apex. The lemmas are deeply cleft into fine, equal-length, prominent teeth that are sharp-pointed or short-awned. Orcuttia tenuis andO. pilosa are found growing together over a portion of their respective ranges but are readily distinguished as described in the discussion of O. pilosa.

Habitat

Slender orcutt grass grows in vernal pools, which are wet in the winter and early spring, and then progressively dry during the late spring and summer.

Distribution

Slender orcutt grass, restricted to northern California, has been extirpated from its type locality in Shasta County and four other sites in the vicinity of the Redding Municipal Airport. Disjunct populations occur in vernal pools on remnant alluvial fans and high stream terraces and recent basalt flows across 220 mi (354 km). This plant has: two populations occurring in Lake County, one in Lassen County, two in Plumas County, two in Sacramento County, 19 (including one translocated) in Shasta County, two in Siskiyou County, and 32 in Tehama County. Thirty-nine populations are on private lands.

In addition to the populations on the The Nature Conservancy's (TNC's) Vina Plains Preserve in Tehama County, The Trust for Public Lands has obtained a conservation easement on the Inks Creek Ranch in Tehama County to protect one population. The City of Redding owns lands containing two populations. The Bureau of Land Management and the U. S. Forest Service have jointly prepared a management guide for one of the ten populations on lands administered by the Bureau of Land Management and three of the nine populations on those lands administered by the Lassen National Forest.

Threats

Although additional populations have been discovered in the last decade, slender orcutt grass is still threatened by habitat loss resulting from land converted to agriculture and urban development. Twenty-three of the 59 native extant populations of are variously threatened by urbanization, altered hydrology, competition from non-native weeds, and off-highway vehicle use.

Conversion of land to agricultural use within the last twenty years is known to have eliminated one population in Shasta County. Agricultural land conversion now threatens two populations in Madera County. Altered vernal pool hydrology can have profound affects on the plants living in that environment, as illustrated by what happened to a population of Slender orcutt grass when the vernal pool that sustained them was channelized for mosquito abatement. The population was extirpated.

Hydrological modifications like this one have destroyed three populations in Shasta County.

In the Sacramento Valley, eight populations in Shasta County are threatened by urbanization around Redding. At least 10 proposed housing developments, golf courses, and landfills in the Sacramento and San Joaquin valleys threaten vernal pool areas that may provide suitable habitat for this taxon. Housing tract developments imperil one population in Shasta County.

The native perennials Eleocharis macrostachya and Eryngium sp. appear to limit distribution and abundance of three populations of slender orcutt grass in Shasta County and 10 populations in Tehama County in the Sacramento Valley. The primary threat to populations of this taxon on TNC's Vina Plains Preserve is competition from invasive alien weeds, including Convolvulus arvensis, Proboscidea louisianica, and Xanthium strumarium.

Off-highway vehicle damage has been reported to one population of O. tenuis in Plumas County and threatens two additional populations in Shasta.

Conservation and Recovery

The Slender Orcutt Grass Species Management Guide written by the Lassen National Forest and the Susanville District of the Bureau of Land Management in 1990 gives long-term management direction for five of 19 Forest Service and Bureau of Land Management plant and animal populations in the northern California counties of Plumas, Shasta, and Siskiyou. Three of the five populations of O. tenuis included in the guide have been fenced since 1990 to protect them from grazing and off-highway vehicle impacts. Since 1990, six additional populations of O. tenuis located on Bureau of Land Management-administered land have been fenced to protect the populations from grazing, although those populations are not currently included in the species management guide. Grazing has also been discontinued in some instances.

Contacts

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/

U. S. Fish and Wildlife Service
Sacramento Field Office
Federal Building
2800 Cottage Way, Room W-2605
Sacramento, California 95825-1846
Telephone: (916) 414-6600
Fax: (916) 460-4619

Reference

U. S. Fish and Wildlife Service. 26 March 1997. "Endangered and Threatened Wildlife and Plants: 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.