Endangered Species Recovery Program

2. Bakersfield Smallscale (Atriplex tularensis)

• Taxonomy
• Description
• Historical Distribution
• Current Distribution
• Life History and Habitat
• Reasons for Decline and Threats to Survival
• Conservation Efforts
• Conservation Strategy

Taxonomy.-- Bakersfield smallscale was named Atriplex tularensis by Coville in 1893 (Skinner and Pavlik 1994). The type specimen was collected 25 kilometers (15 miles) south of Bakersfield on the Tulare Plains of Kern County (Twisselmann 1967). In 1914, Jepson reduced Bakersfield smallscale to a variety of A. cordulata, but Hall and Clements regarded it as a full species in their 1923 publication. The scientific name Obione tularensis was published by Engler and Prantl in 1934 (Niehaus 1977) but was not widely accepted. Taylor and Wilken (1993) used the scientific name Atriplex tularensis for Bakersfield smallscale.

Description.-- In many respects, this species is similar to lesser saltscale because both are annual members of the same genus. However, Bakersfield smallscale has stems up to 80 centimeters (30 inches) tall, has only a few stiff branches, and the leaves may be narrower in proportion to their length (Figure 18). In Bakersfield smallscale, both male and female flowers occur in leaf axils throughout the plant, and the fruits are enclosed in diamond-shaped bracts that are smooth on the surface but toothed on the margin. Bractscale (A. serenana) is a related species that overlaps in range with Bakersfield smallscale. However, unlike Bakersfield smallscale, bractscale has toothed leaf margins, the male flowers occur only at the branch tips, and the fruiting bracts are wedge-shaped or round (Munz and Keck 1959, Freas and Murphy 1988, Taylor and Wilken 1993).

Figure 18. Illustration of Bakersfield smallscale.

Historical Distribution.-- Bakersfield smallscale was restricted historically to a small area of south-central Kern County between Greenfield and ettler (Twisselmann 1969, Skinner and Pavlik 1994, CDFG 1995, Niehaus 1977). Collection localities were Greenfield, Adobe Station, Adobe Road, and Highway 223 (CDFG 1995).

Current Distribution.-- The only extant population believed to represent Bakersfield smallscale is at Gator Pond, which is a remnant of Kern Lake, and formerly part of the Kern Lake Preserve (Figure 19). However, Bakersfield smallscale specimens collected in the area historically differ in appearance from those now present at Gator Pond (D. Taylor pers. comm.).

Figure 19. Distribution of Bakersfield smallscale (Atriplex tularensis).

Life History and Habitat.-- Bakersfield smallscale is a summer annual, germinating from May to June and flowering from June to October (Freas and Murphy 1991, Skinner and Pavlik 1994). Surface soil moisture is required during the summer and fall months for seed germination and seedling survival (Freas and Murphy 1988, Bowen 1986). The population at Gator Pond declined from 721 plants in 1985 to 13 in 1987 and 0 in 1992 as a result of a prolonged drought (Tollefson 1992). Other aspects of the life history and reproductive biology are unknown.

All the populations of Bakersfield smallscale were found on the subalkaline margins of alkali sinks at elevations of 91 to 96 meters (300 to 315 feet). Associated species included alkali heath, glasswort, scratchgrass (Muhlenbergia asperifolia), and saltgrass (Twisselmann 1969, CDFG 1995, Bowen 1986). Other species of concern that occur at Kern Lake are hispid birds-beak and Buena Vista Lake shrew. Comanche Point layia occurred in the vicinity historically (CDFG 1995).

Reasons for Decline and Threats to Survival.-- Like many of the other endangered plants of the San Joaquin Valley, the decline of Bakersfield smallscale was due primarily to agricultural activities (Skinner and Pavlik 1994, CDFG 1995). At most of the historical locations of Bakersfield smallscale, the habitat was completely destroyed by cultivation. At Gator Pond the soil surface was not disturbed, but the hydrology was altered by lowering the water table in the vicinity, leading to conditions too dry for germination and survival of Bakersfield smallscale in all but the wettest years (Bowen 1986, Tollefson 1992).

The Atriplex that now occurs at Gator Pond exhibits characteristics intermediate between Bakersfield smallscale and bractscale. Freas and Murphy (1988) speculated that under the drier conditions, bractscale increased and the two species hybridized. Thus, pure Bakersfield smallscale may be extinct. Even if the two species did not hybridize, the plants at Gator Pond may represent an undescribed form of bractscale (Skinner and Pavlik 1994, Skinner et al. 1995). Another possibility is that Bakersfield smallscale never was a distinct species, but instead was an environmental variant of bractscale that appeared only in years of high rainfall, when soil salinity decreased (Freas and Murphy 1988).

The greatest threat to the continued survival of the annual Atriplex at Gator Pond is conversion to agriculture. The landowner, J. G. Boswell Company, formerly leased the site to The Nature Conservancy as the Kern Lake Preserve, but the lease was not renewed in 1995 (R. Tollefson pers. comm.). Even if the J. G. Boswell Company chooses not to farm the land, the lack of sufficient water to the site threatens the continued existence of the plants.

Conservation Efforts.--Bakersfield smallscale was state-listed as endangered in 1987. During the period when The Nature Conservancy managed the Kern Lake Preserve, the Bakersfield smallscale population was monitored annually. When the population declined precipitously, The Nature Conservancy contracted Stanford Universitys Center for Conservation Biology to study the reasons for the decline. They began greenhouse propagation of plants in 1987, along with research on the site requirements and taxonomy of Bakersfield smallscale (Freas and Murphy 1988). Additional water was provided to the Gator Pond population in 1991. The potential for hydrologic restoration of the site is being studied (K. Freas pers. comm.), and USFWS is negotiating with the J.G. Boswell Company to protect the site (Medlin in litt. 195a). The Kern County Valley Floor Habitat Conservation Plan is expected to provide incentives for protecting the Gator Pond area (T. James pers. comm.).

Conservation Strategy.--The conservation strategy for Bakersfield smallscale is similar to that for lesser saltscale: to protect at least 5 distinct populations numbering at least 1,000 individuals on natural land in blocks of at least 65 hectares (160 acres), with appropriate site management to ensure the continued existence of the species. To accomplish this goal, at least four additional populations must be discovered or established through artificial means, and the Gator Pond population must be increased substantially. Due to the precarious situation at the single known location, all recovery actions for Bakersfield smallscale are high priority. First, Gator Pond must be protected from conversion to other uses, either through a perpetual conservation easement or through transfer of fee title to a conservation entity. Hydrologic restoration of the site also is imperative. These actions also will further conservation of the Buena Vista Lake shrew. Surveys for Bakersfield smallscale should be conducted in the remaining alkali sink areas of Kern County, particularly in years with higher than normal precipitation. However, so little suitable habitat remains in the historic range of the species that four additional populations are not likely to be found during surveys.

Taxonomic studies and research into the effect of soil salinity on morphology (Freas and Murphy 1988) should continue. Also, genetic comparisons should be attempted between Gator Pond plants, bractscale, and related species to determine whether hybridization is possible (D. Taylor pers. comm.). Greenhouse propagation of the Gator Pond plants should continue, and seeds should be collected from any additional populations that are found. When definite Bakersfield smallscale populations are identified (at Gator Pond or elsewhere), introductions to protected alkali sinks in Kern County should begin immediately to bring the total number of sites to five. The status of Bakersfield smallscale should be reevaluated within 5 years of recovery plan approval.