Greene's Orcutt Grass

Tuctoria greenei

Description

Tuctoria greenei was discribed in 1891 as Orcuttia greenei from specimens collected the previous year by Edward Greene near Chico in Butte County. It remained in the genus Orcuttia until Reeder described the genus Tuctoria in 1982 and placed the former O. greenei into this newly named genus.

Tuctoria greenei (Greene's orcutt grass or Greene's tuctoria) is a tufted, more or less pilose, annual grass that grows 2-6 in (5-15 cm) tall. The plant develops several to many erect stems, the outermost decum-bent to spreading at the base, with each terminating in a spike-like inflorescence that may be partially enveloped by the uppermost leaf. The lemmas are strongly curved and more or less truncate at the apex.

Habitat

The Greene's orcutt grass inhabits vernal (or temporary) pools. These are small, seasonally aquatic ecosystems that are inundated in the winter and then dry slowly in the spring and summer. The cyclical wetting and drying creates an unusual and harsh ecological situation that support a unique biota, including the Greene's orcutt grass.

Distribution

Nineteen populations of T. greenei have most likely been extirpated in Fresno, Madera, Merced, San Joaquin, Stanislaus, Tehama, and Tulare counties. The 20 remaining populations of this taxon occur in Butte, Glenn, Merced, Shasta, and Tehama counties. The present range of this species extends 258 mi (567 km). With the exception of one small population of 50 plants on the Sacramento National Wildlife Refuge, all populations are on private lands, including four on the Nature Conservancy's (TNC) Vina Plains Preserve.

Threats

The major threat to T. greenei is habit destruction caused by the conversion of land to agricultural and, to a lesser extent, urban development. Approximately half the known populations of this taxon have definitely been extirpated or appear to have been extirpated by some form of human activity. With the exception of the population on the Sacramento National Wildlife Refuge, the remaining 20 extant populations of T. greenei are variously threatened by, agricultural land conversion, competition from non-native weeds, and grazing.

Conversion of land to agricultural use within the last 20 years is known to have eliminated one population of T. greenei in Tulare County, three in Fresno County, one in Madera County, four in San Joaquin County, two in Stanislaus County, and two in Tehama County. Agricultural land conversion now threatens seven populations of this taxon in Merced County. Irrigated agriculture and associated runoff have likely eliminated one population of T. greenei in Madera County and one in Merced County. Discing combined with grazing has presumably destroyed one population of this plant in Merced County.

Grazing combined with plant competition has proven highly damaging to T. greenei. Soil disturbance from cattle grazing combined with competition from the introduced annual grasses Crypsis schoensides, Phalaris paradoxa, Hordeum geniculatum, and Polypogon monspeliensis and the alien perennial Lolium multiflorum appear to adversely affect two populations of this taxon in Tehama County, one in Butte County within the Sacramento Valley, and all seven remaining extant sites in Merced County in the San Joaquin Valley. T. greenei is quite susceptible to adverse grazing impacts because its preference to grow in vernal pool margins exposes it to damage from livestock trampling and direct competition with the aforementioned aggressive alien plants. One population of this taxon may have been extirpated by 1937 as a result of cattle grazing from a site on private land near Farmington, San Joaquin County; while three populations in Merced County, two populations in Tehama County, and one population in Stanislaus County have not been seen since 1981 and are presumed to be extirpated as a result of cattle grazing. One population of T. greenei in Tehama County, two in Merced County, and one in Butte County are damaged and in decline due to grazing. Cattle grazing occurs on all remaining populations of T. greenei, and this past history of cattle-induced extirpations and declines would strongly indicate that grazing is at least a potential threat to most of the extant populations.

The primary threat to populations of T. greenei on TNC's Vina Plains Preserve is competition from aggressive alien weeds, including Convolvulus arvensis, Proboscidea louisianica, and Xanthium strumarium.

Urbanization has extirpated one population of T. greenei in Tehama County. The Merced County Landfill will destroy vernal pools containing T. greenei.

Existing conservation easements do not adequately protect this plant. Two of the five populations of T. greenei on the Vina Plains Preserve are also damaged and declining due to grazing.

Conservation and Recovery

Only one small population of 50 plants of the Greene's orcutt grass is on the federal land, in the Sacramento National Wildlife Refuge. This habitat should be strictly protected against any threatening influences. Four other populations are on the Vina Plains Preserve of TNC (a private conservation organization), which is being maintained in a natural condition. The other 15 populations of the Greene's orcutt grass are on non-conserved private land, and are at risk of destruction or damage. The largest non-conserved critical habitats on private land should be protected. This could be done by purchasing the land and designating ecological reserves, or by negotiating conservation easements with the landowners. The populations of the Greene's orcutt grass should be monitored, and research undertaken into its biology and habitat needs.

Contacts

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

U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
Eastside Federal Building
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. "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.