National Collection of Imperiled Plants

CPC National Collection Plant Profile

Photographer:

Valerie Soza

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CPC National Collection Plant Profile

Astragalus albens

Family:	Fabaceae
Common Names:	Cushenbury milkvetch, Cushenbury oxytheca, silvery white milkvetch
Author:	Greene
Growth Habit:	Perennial
CPC Number:	7000

Distribution
Protection
Conservation
References

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Photographer: Valerie Soza

Astragalus albens is Not Sponsored

Primary custodian for this plant in the CPC National Collection of Endangered Plants is:

Rancho Santa Ana Botanic Garden

Valerie Soza contributed to this Plant Profile.

Astragalus albens

Astragalus albens is a small, silvery-white, low-growing perennial herb of the pea family. It is a member of an increasingly rare suite of 5 endemic plant species restricted to carbonate deposits in the San Bernardino Mountains of southern California. This attractive plant blooms March-May, producing 5-14 purple flowers at the tips of the stems, which grow to about 1 foot (30 dm) in diameter. Cushenbury milkvetch is a federally-listed endangered species, with nearly all of its sites located on land that is actively mined or maintained for future mining (USFWS 1997).

Distribution & Occurrence

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State Range

California

Habitat

This species is found on cobbly/gravelly soils derived from decomposing limestone bedrock on gentle slopes and in rocky washes that have received limestone outwash. It grows in habitats with open canopies, low competition, and little organic material. Primary associated communities are pinyon-juniper woodlands with blackbush or flannelbush, and blackbrush scrub between 5,000 and 6,600 feet (1,500-2,000 m) elevation (USFWS 1994, 1997).

Distribution

It is distributed over a 15 mile (24 km) stretch on the north side of the San Bernardino Mountains (Transverse Ranges), San Bernardino County, California, from Furnace Canyon southeast to Arrastre Creek, northwest of Tip Top Mountain.

Number Left

Cushenbury milkvetch is known from 30-50 small occurrences with a total estimate of 2,000-7,000 individuals. Sizes of populations fluctuate with rainfall patterns, with larger-sized populations in years of substantial rain (USFWS 1997; Soza pers. comm.).

Protection

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Global Rank:	G1	2/28/2009	Guide to Global Ranks
Federal Status:	LE	8/24/1994	Guide to Federal Status
Recovery Plan:	No	9/1/1997

State/Area Protection

State/Area	Rank	Status	Date

Conservation, Ecology & Research

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Ecological Relationships

Little is known on the pollination ecology, seed dispersal mechanisms, and seedbank dynamics of this species (USFWS 1997).

Threats

Threats and disturbances to the natural habitat of carbonate endemic plants within this region are primarily associated with limestone mining and include destruction of habitat by open or terraced mining techniques and quarries and associated overburden dumping and haul road construction. Mining activities also fragment habitat, alter hydrology, and increase airborne particulates that may depress pollinator success (USFWS 1994). The airborne particulates from existing mine operations have created a hard "cemented" top layer over adjacent slopes, inhibiting water and light penetration, reproduction, seed germination, etc. Many of the populations of Cushenbury milkvetch are located within the San Bernardino National Forest and thus threatened by various recreational activities as well: off-highway vehicle use, ski area expansions, energy development projects, and recreational and urban development near the community of Big Bear Valley and City. In addition, Cushenbury milkvetch populations are small and thus susceptible to stochastic extinction due to random events (USFWS 1994, 1997).

Current Research Summary

Research has been conducted on habitat characteristics of this particular species in the San Bernardino Mountains with respect to restoration potential (Gonella and Neel 1993).

Current Management Summary

The majority of carbonate deposits within the San Bernardino Mountains are owned by the USDA Forest Service, San Bernardino National Forest (SBNF), which has developed a forest management plan that aims to conserve some of the existing populations of the carbonate endemics by setting aside refugia. As part of this plan, the SBNF has supported ongoing surveys of carbonate habitat within the SBNF to expand knowledge of species distribution patterns and assist in identification of refugia potential (USFWS 1997).

Research Management Needs

Management needs that have been identified by the USFWS include protection of significant extant populations by developing a reserve system on federally owned land of occupied areas, buffer zones, and habitat connections; restoring habitat, reintroduction efforts and enhancing populations; monitoring populations; and conducting surveys and taxonomic assessments to locate new populations and resolve questions about the identity of several existing populations (USFWS 1997).

Ex Situ Needs

References

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Books (Single Authors)

Barneby, R.C. 1964. Atlas of North American Astragalus. Bronx, New York: New York Botanical Garden. 1188p.

Books (Sections)

Kartesz, J.T. 1999. A synonymized checklist of the vascular flora of the U.S., Canada, and Greenland. In: Kartesz, J.T.; Meacham, C.A., editors. Synthesis of the North American Flora, Version 1.0. North Carolina Botanical Garden. Chapel Hill, NC.

Conference Proceedings

Gonella, M.P.; Neel, M.C. Characterizing rare plant habitat for restoration in the San Bernardino National Forest. Proceedings: wildland shrub and arid land restoration symposium. Gen. Tech. Rep. INT-GTR-315. Ogden, UT: U.S. Department of Agriculture, Forest Service, Intermountain Research Station; October 19-21; Las Vegas, NV. 1993.

Electronic Sources

(2000). CalFlora: on California plants for education, research and conservation. [web application]. Berkeley, California: The CalFlora Database [a non-profit organization]. http://www.calflora.org/.. Accessed: 2002.

CNDDB. (2000). Calfornia Natural Diversity Data Base (CNDDB). Version 2.1.2. California Natural Diversity Database. Accessed: California Department of Fish and Game, Sacramento.

Journal Articles

Krantz, T. 1988. Limestone Endemics of Big Bear Valley. Fremontia. 16, 1: 20-21.

Neel, M.C.; Cummings, M.P. 2003. Effectiveness of conservation targets in capturing genetic diversity. Conservation Biology. 17: 219-229.

USFWS. 1991. Proposed Endangered Status for Five Limestone Endemic Plants from Southern California. Federal Register. 65, 223: 58332-.

USFWS. 1992. Listing Proposals. Endangered Species Technical Bulletin. 17, 1-2: 9-10.

USFWS. 1994. Five plants from the San Bernardino Mountains in southern California determined to be threatened or endangered. Federal Register. 59, 163: 43652-43664.

USFWS. 2002. Proposed Designation of Critical Habitat for Five Carbonate Plants From the San Bernardino Mountains in Southern California. Federal Register. 67, 29: 6578-6612.

Reports

Stephenson, John R.; Calcarone, Gena M. 1999. Southern California Mountains and Foothills Assessment: Habitat and Species Conservation Issues. Chapter 5 - Potentially Vulnerable Species: Plants. Albany, CA: Pacific Southwest Research Station, Forest Service, U.S. Department of Agriculture. p.402. General Technical report PSW-GTR-172.

USFWS. 1997. San Bernardino Mountains Carbonate Plants Draft Recovery Plan. Portland, Oregon: U.S. Fish and Wildlife Service. p.51.

Theses

Gonella, Michael Paul. 1994. Characterization of Rare Plant Habitat for Restoration in the San Bernardino National Forest. [M.S. Thesis]: San Jose State University. 151p.

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This profile was updated on 3/4/2010