San Joaquin Adobe Sunburst
San Joaquin Adobe Sunburst
|Listed||February 6, 1997|
|Description||Erect annual herb loosely covered with white, woolly hairs; flowers are bright yellow.|
|Habitat||On heavy adobe clay soils in three Central Valley, California, counties.|
|Threats||Residential development and urbanization, agricultural land development, flood control projects, transmission line maintenance, non-native plant competition, inappropriate grazing practices, road construction and repairs.|
San Joaquin adobe sunburst, Pseudobahia peirsonii, is an erect annual herb about 4-18 in (10.2-46.4 cm) tall, loosely covered with white, woolly hairs. Its alternate leaves are twice divided into smaller divisions (bipinnatifid), triangular in outline, and 1-3 in (2.5-7.6 cm) in length. Flower heads, which appear in March or April, are solitary at the ends of the branches. The ray flowers are bright yellow and equal in number to the subfloral bracts and about 0.1 in (0.3 cm) long with many disk flowers; the pappus is absent. The dry fruits, called achenes, are black. San Joaquin adobe sunburst is distinguished from P. heermani, the species most similar in appearance, primarily by its subfloral bracts, which are united only at the base versus united to half their length in the latter species.
San Joaquin adobe sunburst occurs only on heavy adobe clay soils in three Central Valley counties. Scientists have recently speculated that the edaphic restriction is associated with the ability of these clay soils to retain moisture longer into the summer dry season. These soils are mainly distributed in the valleys and flats near the foothills of the southeastern San Joaquin Valley. The intrusive and aggressive characteristics of herbaceous weedy species appear to be detrimental to habitat quality of this rare plant.
San Joaquin adobe sunburst occurs over a range of approximately 120 mi (193 km) through Fresno, Tulare, and Kern Counties. This taxon is now found only in a small number of isolated colonies in the southeastern portion of the San Joaquin Valley: the Round Mountain region in Fresno County, the Porterville-Fountain Springs region in Tulare County, and the Pine Mountain-Woody region in Kern County.
Of the 36 known occurrences, 20 populations are small and contain fewer than 250 plants, while 12 contain 1,000 or less plants. Approximately 80% of all plants are contained in four populations. One population occurs on land owned and managed by the Fresno Flood Control District, two populations occur on land owned by the U. S. Army Corps of Engineers, and all other populations occur on privately owned land.
The primary threat to this species is habitat loss, degradation, and alteration brought about by residential development and the increased urbanization that comes in its wake. Other significant threats to populations of San Joaquin adobe sunburst include agricultural land development, flood control projects, transmission line maintenance, non-native plant competition, inappropriate grazing practices, and road construction and repairs. These activities collectively have reduced the species to a small number of isolated colonies that occur in locations east of Fresno in Fresno County, west of Lake Success in Tulare County, and northeast of Bakersfield in Kern County. Agricultural land development, urbanization, flooding and shore erosion at Lake Success, recreational activities, grazing, and water projects have extirpated eight historical occurrences that were in Tulare County.
The largest population, containing approximately 5,000 plants spread over 3 acres (1.2 hectares), is being adversely affected by the large Quail Lakes residential project and an adjacent recreational water park named Clovis Lakes. The Quail Lakes project consists of a 51-acre (20.6-hectare) lake and 730 housing units spread over 375 acres (151.8 hectares).
The second-largest population of San Joaquin adobe sunburst, with nearly 4,500 plants spread over 42 acres (17 hectares) in Fresno County, is located in the Fancher Creek Reservoir Project Area. The Fancher Creek Reservoir Project was constructed several years ago by the Fresno Metropolitan Flood Control District to temporarily detain water during flood periods, which it has done at various times over the past two years. The project was predicted to affect approximately 40% of this population. The three other Fresno County sites are threatened variously by the gradual conversion of rangeland in eastern San Joaquin Valley to residential use as the greater Fresno area expands, agricultural development, incompatible grazing practices, competition from non-native plants, and livestock trampling.
Most Tulare County populations of San Joaquin adobe sunburst lie in the Porterville-Fountain Springs area, although several small, isolated populations recently have been discovered in the northern part of the county. Maintenance and repair of the Southern California Edison transmission lines pose a potential threat to two Tulare County populations of this species located under the transmission line right-of-way south of Fountain Springs. Another population, located near the high water line at Lake Success east of Porterville, could be impacted or extirpated by inundation or erosion resulting from a rise in water level. Although the corps has no current plans to increase water storage, such a project has been proposed in the recent past.
Non-native species germinate in late fall and likely outcompete San Joaquin adobe sunburst for sunlight, nutrients, and water. Competition from non-native plants threatens four occurrences of San Joaquin adobe sunburst in Tulare County.
Excessive trampling of the plants by livestock may also be detrimental because of direct and indirect effects of ground compaction on soil-water relations and erosion. One historical occurrence in Tulare County of San Joaquin adobe sunburst is thought to have been extirpated by incompatible grazing practices.
Numerous other human impacts threaten populations of San Joaquin adobe sunburst. Potentially harmful runoff from State Route 180 in Fresno County may harm a population growing on the soft shoulders of both sides of the highway. Road stabilization and maintenance practices threaten four populations in Kern County, three in Tulare County, and two in Fresno County. Off-road vehicle use and hiking threaten one population of approximately 200 plants spread over 3 acres (1.2 hectares) in Tulare County.
Conservation and Recovery
Part of the mitigation for the project includes preservation of the two highest density of four sub-populations of San Joaquin adobe sunburst on the site and the establishment of a third new subpopulation using topsoil salvaged from an area to be destroyed. The salvaged topsoil would be planted with seeds collected from a high density population eliminated by the project. Whether this proposed mitigation will work is questionable, since propagation of rare species is frequently unsuccessful. In a study funded by the California Department of Fish and Game, 40 projects attempting to transplant, relocate, or reintroduce endangered or threatened plant species in California were evaluated; only 20% of the projects were deemed fully successful.
U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
Eastside Federal Complex
911 N. E. 11th Ave.
Portland, Oregon 97232-4181
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.