Cushenbury Buckwheat

Eriogonum ovalifolium var. vineum

Description

Eriogonum ovalifolium var. vineum (Cushenbury buckwheat) is a low and densely-matted perennial of t he buckwheat family (Polygonaceae) that flowers from May through June. Whitish-cream flowers that darken to a reddish or purple color with age are borne on flowering stalks 4 in (10 cm) in height. The round to ovate leaves are white-woolly on both surfaces and are 0.3-0.6 in (1-1.5 cm) long. The diameter of mats is typically 6-10 in (15-25 cm), but may reach up to 20 in (50 cm) in particularly well-developed individuals.

Habitat

Cushenbury buckwheat occurs within openings of pinyon woodland, pinyon-juniper woodland, Joshua tree woodland, and blackbrush scrub communities at elevations between 4,600-7,900 ft (1,400-2,400 m). Other habitat characteristics include open areas with little accumulation of organic material, a canopy cover generally less than 15%, and powdery fine soils with rock cover exceeding 50%. The plant typically occurs on moderate slopes, although a few occurrences are on slopes over 60%. On milder, north-facing slopes, it co-occurs with Cushenbury milk-vetch.

Distribution

Fieldwork undertaken in 1992 refined the information on the carbonate geology of the San Bernardino Mountains. Cushenbury buckwheat clearly occurs on limestone substrate in the White Knob area and from Arctic/Bousic Canyon west to Terrace Springs, south to Top Spring, and along the north side of Lone Valley to Tip Top Mountain. However, this species occurs on dolomite in the Bertha Ridge area, north Holcomb Valley, Jacoby Canyon, and along Nelson Ridge. Additionally, a population just to the south of Mineral Mountain is clearly on noncarbonate substrates; a population in Furnace Canyon seems to be on a mixed lithology of granite, limestone, and dolomite; and a population on Heartbreak Ridge is on carbonate substrate.

Cushenbury buckwheat was known from approximately 20 occurrences in 1997, all of them confined to a 25 mi (40 km) portion of the carbonate substrate belt on the north slopes of the San Bernardino Mountains between the White Knob area east to Rattlesnake Canyon. Surveys conducted in 1988 resulted in a slight range extension of the plant in the Rattlesnake Canyon drainage. The 1992 discovery of a previously unknown population west of White Knob extended the known range of the plant west by 1 mi (1.6 km). A dozen other extensions of existing occurrences were reported by the Forest Service; all of these were within the known range of the plant. Since publication of the listing proposal in August of 1994, additional Forest Service surveys have located two previously unknown populations, one near Jacoby Springs and one just north of Mineral Mountain. In 1988, only a quarter of the then known occurrences comprised more than 1,000 individuals each, with the total population numbering approximately 13,000 individuals.

Threats

Cushenbury buckwheat is restricted primarily to carbonate and adjacent carbonate/granitic substrates occupied by pinyon-juniper woodland on the northern side of the San Bernardino Mountains. The imminent and primary threat facing this species is the ongoing destruction of the carbonate substrates on which it grows by activities associated with limestone mining, including direct removal of mined materials, disposal of overburden on adjacent unmined habitat, and road construction. Additional threats to its habitat include off-highway vehicle use, urban development near the community of Big Bear, development of a ski run, and energy development projects.

Conservation and Recovery

Critical habitats of the Cushenbury buckwheat are threatened by a wide range of human activities. About 80% of its occurrences are on federal land, mostly managed by the Forest Service. These critical habitats should be protected from mining and other disturbances. This could be done by appropriate modifications of the management plan for the San Bernardino National Forest. The populations of the Cushenbury buckwheat should be monitored, and research undertaken into its biology and habitat requirements.

Contacts

U.S. Fish and Wildlife Service
Ventura Fish and Wildlife Office
2493 Portola Road, Suite B
Ventura, California 93003-7726
Telephone: (805) 644-1766

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/

References

U.S. Fish and Wildlife Service. 24 August 1994. "Endangered and Threatened Wildlife and Plants; Five Plants From the San Bernardino Mountains in Southern California Determined to be Threatened or Endangered." Federal Register 59.