Burke's Goldfields

Lasthenia burkei

Description

Burke's goldfields is an annual in the aster family that grows to a height of about 12 in (30.5 cm). The lanceolate leaves are arranged in opposite pairs. Flower heads, consisting of bright yellow ray and disk flowers, bloom from April through June. It is distinguished from similar goldfields species by certain seed characteristics. The species has also been known as Baeria burkei.

Habitat

This species is limited to vernal pools and other seasonal wetlands in Lake County, California, and in the Cotati Valley, which lies north of San Francisco. These pools form where non-porous material, such as clay, hardpan, or volcanic stone, underlies surface depressions. In these areas, winter rains form pools that gradually dry out during the spring and summer. This unique habitat is not suitable for species that are intolerant of inundation or for aquatic species that require permanent standing water.

Two other Endangered plant species are found in Cotati Valley vernal pools: Sebastapol meadow-foam (Limnanthes vinculans ) and Baker's sticky seed (Blennosperma bakeri ) . These species occur in an area of Sonoma County about 16 mi (25.8 km) long and from 5-11 mi (8-17.7 km) wide. This range is bounded on the north by Windsor; on the south by the town of Hessel; on the west by the Laguna de Santa Rosa, a tributary of the Russian River; and on the east by the foothills of the Sonoma and Mayacmas Mountains. In the Cotati Valley, vernal pools form on Huichica loam and Clear Lake clay soil types where there is an impervious layer 2-3 ft (0.6-0.9 m) below the surface.

Other plants associated with these vernal pools include fringed downingia (Downingia concolor ), Navarretia spp., smooth lasthenia (Lasthenia glaberrima ) , and Lobb's buttercup (Ranunculus lobbii ).

Distribution

Burke's goldfields was first collected in 1886 near Ukiah in Mendocino County, California. It has also been found in Sonoma and Lake Counties.

At present there are 34 known populations of Burke's goldfields, all but one in the Cotati Valley. These sites are concentrated in the northern portion of the valley, near Windsor. Most of the valley's vernal pools are privately owned; however, three are within the rights-of-way owned by the California Department of Transportation, and four are owned by county or city agencies. The species is also found on private property at Manning Flat in Lake County. The discovery site near Ukiah has not been relocated and the continued existence of the species there is unknown.

Threats

The overwhelming threat to Burke's goldfields and other vernal pool species is the destruction of their unique habitats for residential and agricultural development. So far about 90% of the Cotati Valley has been developed. The need for affordable housing within commuting distance of San Francisco has increased developmental pressure throughout the valley.

The construction of housing developments near Windsor is destroying populations of Burke's goldfields. Recently more than a dozen pools have been filled without the landowners obtaining permits from the U.S. Army Corps of Engineers required by the federal Clean Water Act. In part because most of the pools are relatively small, the Corps of Engineers has been reluctant to involve itself in examining the ecological effects of filling these seasonal wetlands. Now that Burke's goldfields and other vernal pool species have been listed under the Endangered Species Act, the corps must consult with the U.S. Fish and Wildlife Service whenever alteration of their habitat is proposed, regardless of the size of the wetland.

Sonoma County has approved a development plan for Windsor which, if fully implemented, would destroy most, if not all of the vernal pools in the northern reaches of the valley—about 35% of the species' range.

A lesser threat to Burke's goldfields is livestock grazing, which has reduced populations of endemic vernal pool species at many of their historic sites.

Conservation and Recovery

The Burke's goldfields is known from about 42 sites, but most of its original critical habitats are now destroyed or degraded. The remaining vernal-pool and intermittent-swale habitats of this rare plant must be protected from destruction or damage by pollution, excessive grazing by livestock, in-filling, or irrigation. The habitat must also be managed to prevent or repair damage caused by invasive, non-native plants. All of the critical habitats of the Burke's goldfields are privately owned. The most important sites should be protected by acquiring them and establishing ecological reserves, or by negotiating conservation easements with the landowners. The populations of the Burke's goldfields should be monitored and field surveys undertaken to determine whether additional ones occur. Research should be undertaken into its biology and ecology, including work to develop appropriate management practices to conserve its critical habitat. Some work has investigated the possibility of creating "new" vernal-pool habitats for the Burke's goldfields and other wetland species, and this research in ecological restoration should be continued (although the highest priority should be the protection of natural vernal-pool habitats). The Burke's goldfields can be cultivated in horticulture, but it is esstential that viable populations be conserved in natural habitats.

Contacts

Regional Office of Endangered Species
U.S. Fish and Wildlife Service
Eastside Federal Complex
911 N.E. 11th Ave.
Portland, Oregon 97232
http://pacific.fws.gov/

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

References

Holland, R. F. 1976. "The Vegetation of Vernal Pools: A Survey." In Vernal Pools: Their Ecology and Conservation, a symposium sponsored by the Institute of Ecology, University of California, Davis, May 1 and 2, 1976. Institute of Ecology Publication No. 9.

Jain, S. 1976. "Evolutionary Studies in the Mead-owfoam Genus Limnanthes, an Overview." In Vernal Pools: Their Ecology and Conservation, a symposium sponsored by the Institute of Ecology, University of California, Davis, May 1 and 2, 1976. Institute of Ecology Publication No. 9.

Ornduff, R. 1966. "A Biosystematic Survey of the Goldfield Genus Lasthenia (Compositae: Heleniae)." University of California Publications in Botany 40:1-92.

Ornduff, R. 1977. "Rare Plant Status Report for Lasthenia burkei. " California Native Plant Society, Sacramento.

Waaland, M. 1989. "Santa Rosa Plains Endangered Plant Protection Program Report, Section A." Sonoma County Planning Department and California Department of Fish and Game.