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Post by Melanie on Jan 27, 2007 1:09:58 GMT 1
Ventura Marsh Milkvetch – Astragalus pycnostachyus var. lanosissimus
The Ventura Marsh Milkvetch was rediscovered in 1997 near Oxnard on a
disturbed site after not being found anywhere within its historic
range since 1967. Channel Islands Chapter member Kate Symonds found
the plant. The site at which it was found is an old oil waste
dumpsite, which is proposed to be developed for housing, after the
developer clean up the contamination onsite. Clearly, the Ventura
Marsh Milkvetch appeared onsite after the dump had been closed.
Where did the seeds come from? No one knows, but botanist David
Magney suspects they came from soil excavated from the site near
McGrath State Beach where it had last been seen in 1967.
Attempts to propagate this plant from cuttings and seed are underway,
and experiments are underway to find out more about the ecological
requirements of this rare taxon. The California Department of Fish
and Game is funding propagation efforts and ecological studies, with
the hopes to reestablish this listed endangered species in the wild
as soon as possible. CNPS member David Magney submitted a listing
petition to the California Fish and Game Commission in 1998, which
was accepted, and it is now both state and federally listed as an
endangered species. See the articles under Issues for more
information about the North Shore Development in Oxnard.
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Post by Melanie on Jan 31, 2007 16:46:03 GMT 1
Astragalus pycnostachyus var. lanosissimus
Less than 50 plants are known to exist, represented by a single population. The population occurs on an abandoned oil-field waste site, which has been proposed for reclamation and development as a residential community. Historic records suggest that this variety occurred near coastal marshes or bodies of brackish water, often on well-drained substrates near the water table. The current population occurs on an artificially compact substrate composed on clay, sand, and small gravels, above a water table that lies between 3 and 5 feet below the surface, and which is contaminated by oil wastes. Despite this seemingly inhospitable habitat, the population has remained relatively stable and plants have produced flowers and fruits during most of the years since its discovery in 1997.
Habitat Well-drained soils of open sites in coastal habitats, often on bluffs or flats near bodies of brackish water or with a relatively high water table, in association with dune or coastal shrubland vegetation. The distribution of the closely related northern marsh milkvetch (Astragalus pycnostachyus var. pycnostachyus, historic records, and the location of the single known population suggests that this species may survive where summer fog ameliorates the otherwise hot summers.
Distribution Known only from a single, self-sustaining population in Oxnard, Ventura County, California. Historical records indicate the occurrence of as many as 4 or 5 sites along the coast between Ventura and Orange counties, California.
Number Left Only one putatively natural population is left. It is in Oxnard, Ventura County, California. The remaining population has been composed of 30-50 reproductive plants per year, but as many as 300 vegetative plants have been observed during years with above normal precipitation and cool summers. Through efforts by the California Department of Fish and Game, small experimental populations have been established at four protected sites with comparable habitats in Santa Barbara and Ventura counties. The purpose of the experimental populations is to assess potential habitats for recovery, and to provide insurance against catastrophic loss.
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Post by Melanie on Jan 31, 2007 16:46:32 GMT 1
Ecological Relationships They include well-drained soils of open sites in coastal shrublands or dune swales, near bodies of fresh or brackish water. Associated native species include Baccharis pilularis, Malosma laurina, and Toxicodendron diversilobum. The single known population is found in close proximity to the coast, where summer fog ameliorates the otherwise dry, warm to hot days.
Threats • Herbivory by nonnative milk snails, which feed on seedlings and young vegetative shoots.
• Infestation by cucumber mosaic virus, which is vectored by aphids.
• Herbivory of seeds by weevils, which reduce seed set to less than 2 seeds in infested fruits.
• Competition from alien weeds (primarily ice plant and white sweet clover).
• Catastrophic loss of the last remaining population.
Current Research Summary Research conducted by the Santa Barbara Botanic Garden focused on reproductive biology and ecological requirements. Seedling cohorts show high mortality, especially from herbivory by snails, and during several seasons from below normal rainfall (Wilken and Wardlaw 2001). Research conducted by Rancho Santa Botanic Garden showed that seed germination is best accomplished through scarification, and that mature plants could be successfully transplanted, if provided sufficient water during the first season after planting. Survivorship of experimental populations was highest at sites with high water tables providing fresh or brackish water, as compared to salt water from nearby salt marshes (Soza et al. 2003).
Current Management Summary The single remaining population is on privately owned land and has been fenced to protect it from accidental incursion by vehicles or individuals. Weed removal, snail abatement, and other protective measures are being conducted by volunteers and Department of Fish and Game staff. Experimental populations are protected by their location on state park lands, and their location at sites that are infrequently used by the public.
Research Management Needs • Protection and augmentation of experimental populations.
• Genetic analysis of natural and experimental populations.
• Surveys for additional recovery sites.
Ex Situ Needs Augmentation of the conservation collection through managed cultivation of genetic lineages derived from separate plants at the original site.
References Top
Books (Single Authors)
Hickman, J.C. 1993. The Jepson manual: Higher plants of California. Berkeley: University of California Press. 1400p.
Jones, M. 1923. Revision of the North American species of Astragalus. Salt Lake City, Utah: Published by the author. 288p.
Munz, P. 1974. A flora of southern California. Berkeley: University of California Press. 1086p.
Books (Sections)
Soza, V. M. Wall, and D. Hannon. 2003. Experimental introduction of the Ventura marsh milkvetch (Astragalus pycnostachyus var. lanosissimus) at Carpinteria Salt Marsh Reserve and McGrath State Beach. Rancho Santa Ana Botanic Garden. p 30.
Wilken, D. and T. Wardlaw. 2001. Ecological and life history characteristics of Ventura marsh milkvetch (Astragalus pycnostachyus var. lanosissimus) and their implications for recovery. Santa Barbara Botanic Garden. p 55.
Journal Articles
USFWS. 1999. Proposed endangered status for Astragalus pycnostachyus var. lanosissimus (Ventura Marsh Milkvetch). Federal Register. 64, 100: 28136-28142.
USFWS. 2001. Final rule for endangered status for Astragalus pycnostachyus var. lanosissimus (Ventura marsh milkvetch). Federal Register. 66, 98: 27901-27908.
Maps
Barneby, R.C. 1964. Atlas of North American Astragalus. Memoirs of the New York Botanical Garden. Volume 13: 1-1118.
Reports
Ikeda, D. and M. Meyer. 2000. Report to the Fish and Game Commission on the status of Ventura marsh milk-vetch (Astragalus pycnostachyus var. lanosissimus). Status Report 2000-1. Sacramento, California: p.50.
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Post by Melanie on Jan 31, 2007 16:47:07 GMT 1
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Post by Surroundx on Jan 24, 2020 11:31:21 GMT 1
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Post by koeiyabe on Jun 19, 2020 15:57:41 GMT 1
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Post by koeiyabe on Jan 10, 2021 5:19:42 GMT 1
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