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Comparative Demography of Three Sensitive and Morphologically Similar Species of Astragalus
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Special status plants are those recognized by either state or federal governments as being potentially threatened with extinction. These include proposed or listed species under the U.S. Endangered Species Act or by state regulation and species suspected to be threatened or endangered. Resource managers of federal and state lands are mandated to sustain these extant populations on their lands. To meet this mandate, managers need to understand the natural dynamics of these species and how management options may influence these dynamics. Three species within the Astragalus genus, A. oniciformis Barneby (Picabo milkvetch), A. mulfordiae (Mulford's milkvetch), and A. peckii (Peck's milkvetch), are currently of management concern for BLM districts in Oregon and Idaho. Basic demographic data have never been collected for these species other than estimates of population sizes through field surveys by BLM staff or through status reports. Effects of animal grazing, and the effects of wildfires and subsequent revegetation practices are two potential threats to these species. This project will collect five years of demographic data (i.e., reproduction and survival) for all three species to identify natural population dynamics of these species. For A. peckii, where livestock grazing has a potential impact, demographic data will be compared between grazed and ungrazed populations. For A. mulfordiae and A. oniciformis, the impact of wildfire rehabilitation using a species mix that includes Agropyron desertorum ('Nordan' crested wheatgrass), a grass that is more competitive than native bunchgrasses will be examined. For A. peckii, environmental data related to each population will be collected to identify potential site requirements for sustaining A. peckii populations.
Kaye, T.N., Pyke, D.A., 2003, The effect of stochiastic technique on estimates of population viability from transition matrix models: Ecology, v. 84, no. 6, p. 1464-1476. [Highlight] [FullText] Catalog No: 1210 Alexander, J.A., 2001, Genetic Diversity of Populations of Astragalus oniciformis Using Inter-simple Sequence Repeat (ISSR) Markers Associated Appendices: Corvallis, OR, Oregon State University, 90 p. [FullText] Catalog No: 1030 Miller, H.C., Clausnitzer, D., Borman, M.M., 1999, Medusahead In Sheley, R.L., Petroff, J.K., eds., Biology and management of noxious rangeland weeds: Corvallis, OR, Oregon State University Press, p. 271-281. [FullText] Catalog No: 598 Clausnitzer, D., 1996, Competition between squirreltail and medusahead- Final report: USGS, Forest and Rangeland Ecosystem Science Center, p. 18. [FullText] Catalog No: 539 Clausnitzer, D., 1996, Field Study of Competition between Medusahead (Taeniatherum caput-medusae ssp. Asperum (Simk.) Melderis) and Squirreltail (Elymus elymoides (Raf.) Swezey)--M.S. thesis: Corvallis, OR, Oregon State University, 40 p. Catalog No: 540
Population Viability Analysis - Annual Transition Matrices
Pyke, David A. - Supervisory Research Ecologist
Phone: 541-750-7334
Email: david_a_pyke@usgs.gov
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