Hartweg's Golden Sunburst
Hartweg's Golden Sunburst
|Listed||February 6, 1997|
|Description||Few-branched annual covered with white woolly hairs.|
|Habitat||The top of Mima mound topography where the grass cover is minimal.|
|Threats||Residential development; agricultural development; competition from aggressive exotic plants; incompatible grazing practices; mining; off-road vehicle use.|
Hartweg's golden sunburst (Pseudobahia bahiifolia ) is a few-branched annual about 2-6 in (5.1-15.2 cm) tall, covered throughout with white woolly hairs. Its leaves are narrow, alternate, three-lobed or entire with three blunt teeth at the apex, and about 0.4-0.8 in (1-2 cm) long. The bright yellow flower heads, produced in March or April, are solitary at the ends of the branches. The ray flowers are equal in number to the subfloral bracts, and the pappus is absent. P. bahiifolia is distinguished from other members of the genus by having the largest leaves.
Hartweg's golden sunburst prefers the top of Mima mound topography where the grass cover is minimal. Vernal pools, an increasingly rare California land-form, are often interspersed with the Mima mounds.
The range of Hartweg's golden sunburst is strongly correlated with the distribution of the Amador and Rocklin soil series. Both series generally consist of shallow, well-drained, medium-textured soils that exhibit strong Mima mound microrelief. Such topography is characterized by a series of mounds that may range from 1-6.6 ft (0.3-2 m) in height and to 98 ft (29.9 m) in basal diameter, interspersed with shallow basins that may pond water during the rainy season.
Hartweg's golden sunburst nearly always occurs on the north or northeast facing slopes of the mounds, with the highest plant densities on upper slopes with minimal grass cover. A variant of one of the two soil series is concentrated near Friant in Madera County and contains large quantities of pumice, which is mined for use as an industrial binder and is used in making concrete blocks.
Hartweg's golden sunburst may have existed throughout the Central Valley of California from Yuba County in the north to Fresno County in the south, a range of approximately 200 mi (321.9 km). It is now known from only 16 sites in two localized areas in the eastern portion of the San Joaquin Valley, a range of approximately 95 mi (152.9 km)—the Friant region in Madera and Fresno Counties and the Cooperstown-La Grange region in Stanislaus County. One population occurs on land owned and managed jointly by the U.S. Bureau of Reclamation (BOR) and a private owner; the remaining populations all occur on privately owned property.
More than 90% of all Hartweg's golden sunburst plants are found in the two aforementioned general locations. The site in Madera County, approximately 0.5 mi (0.8 km) long and containing about 16,000 plants, is the remnant of one large population that has become fragmented. The site in Stanislaus County covers about 5 acres (2 hectares) and contains approximately 15,000 plants. Although the number of individuals per population of annual species is highly variable from year to year, 11 of 16 extant populations are very small, numbering fewer than 200 plants during the 1990 field season.
Conversion of native habitat to residential development is the primary threat to the existence of Hartweg's golden sunburst. Plant populations in all three counties are also threatened by habitat destruction and alteration from agriculture development, competition from aggressive exotic plants, incompatible grazing practices, mining, and off-road vehicle use. Urbanization and agricultural land development eliminated the type locality in Yuba County, the only documented occurrence of this plant in the Sacramento Valley. The species likely was extirpated in the area between Stanislaus and Yuba Counties before other collections were documented, as valley soils in this area were rapidly converted to agricultural use in the late 1800s.
Two historical occurrences of Hartweg's golden sunburst have been eliminated or seriously degraded in Madera County by conversion to orchards, mining, unauthorized dumping, and grazing. The remaining populations in Madera County, including the one with 16,000 individuals that represents approximately half of all plants of this species, are at grave risk for elimination by a residential development project. The Madera County occurrences are also threatened by quarry activities and off-road vehicle use. Another quarry in Stanislaus County is located 0.25 mi (0.4 km) east of the second-largest population of Hartweg's golden sunburst—a population of about 15,000 plants.
Although there are no current plans to expand either mining operation, the threat of expansion is dependent upon product demand. Moreover, degradation from off-road vehicle use on these sites is ongoing. Grazing occurs at both locations and appears to be accelerating soil erosion at the smaller site. All of these problems are compounded because neither location is protected.
Conservation and Recovery
In Fresno County, one population grows on three land parcels, two of which are protected. One parcel is jointly managed by the BOR and the Nature Conservancy, and one parcel is protected by conservation easement. The third parcel is in private ownership and is threatened by incompatible grazing practices and residential development. The other Fresno County population occurs entirely on private lands. Both privately held Fresno County occurrences are threatened by 1) urbanization associated with the Millerton New Town development, 2) the Friant Re development Plan, 3) incompatible grazing practices, and 4) water tank access and maintenance.
In the Cooperstown-La Grange area of Stanislaus County, three of the remaining dozen occurrences are variously threatened by off-road vehicle use, incompatible grazing practices, erosion resulting from overgrazing, potential quarry expansion, and agricultural land development. At one of the three threatened sites, habitat was present but no Hartweg's golden sunburst plants were found during the 1990 survey. The remaining nine populations, all of which occur on private land, each contain less than 250 plants. Although the populations appear to be stable under current grazing practices, they may suffer if grazing pressures increase or land use is changed.
Non-native species germinate in late fall and likely outcompete Hartweg's golden sunburst for sunlight, nutrients, and water. Competition from non-native plants threatens the Hartweg's golden sunburst population at the botanical preserve in Fresno County.
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
U. S. Fish and Wildlife Service. 6 February 1997. "Determination of Endangered Status for Pseudobahia bahiifolia (Hartweg's Golden Sun-burst) and Threatened Status for Pseudobahia peirsonii (San Joaquin Adobe Sunburst), Two Grassland Plants from the Central Valley of California." Federal Register 62 (25): 5542-5551.