Conservation ecology and life history observations for the Malheur prince’s plume (Stanleya confertiflora: Brassicaceae): 2007 demographic field work summary

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Abstract:

This is the 2007 field season summary for the multi-year Stanleya confertiflora monitoring project on the Burns and Vale BLM Districts. It represents the latest of several contiguous years of observation and sampling of the species in southeast Oregon, and is provided here in the form of an addendum to the much more comprehensive 2005 report provided to BLM. The latter was a broad synopsis that reviewed several summers worth of demographic records through 2005, and provided a wide range of data and observations on the natural history and ecology of the species. The ultimate objective here has been to use these years of observations and measurements as a means for developing an overall conservation and status assessment for the species across its range in Oregon and Idaho, which is expected to be initiated in 2008. <br> Stanleya confertiflora is a biennial species, an uncommon plant life history strategy yet certainly not unheard of in native mustards. Large plumes of flowers and many thousands of seed are typically produced by each Stanleya plant that reaches maturity and avoids being grazed. The seeds are dormant when dispersed and require cold stratification to germinate. Earlier work has shown that the species is mostly flowering and reproductive in alternate years, with intervening years primarily represented by vegetative and non-reproductive plants. Field inventories for the species should be restricted to “reproductive” years and avoided during years when populations are known or expected to be mainly vegetative, since the size and coloration of juvenile plants makes them difficult to observe. Data collected over the last several seasons also indicate that the life history of Stanleya populations across the range of the species may show some degree of synchronization, i.e., where the majority of populations in a given year will principally consist of either non-reproductive juveniles, or bolted reproductive plants. <br> Precipitation amounts and timing, combined with demographic data from prior monitoring, may be useful in predicting whether or not Stanleya plants will make a significant appearance in any given year, and whether or not they will be reproductive. Although there appear to be many thousands of acres of potential habitat for Stanleya confertiflora in southeast Oregon and adjacent Idaho, comparatively few populations for the species have been discovered (with most of these relatively small) considering the expanse of its natural range, and it continues to be an enigmatic and potentially endangered species. The limited number of sites are likely related to edaphic requirements that have yet to be fully understood and described, particularly for the western populations in Harney County, Oregon. <br> Populations are either white- or yellow-flowered, and these floral phenotypes are segregated geographically as well. The conservation significance of the two color forms may be more important than initially believed from earlier studies, and requires additional research. <br> Investigations directed specifically at determining the effects of grazing on Stanleya confertiflora have not been implemented. However, circumstantial evidence collected during the course of this project (including observation in 2007) suggests that cattle grazing on public lands may pose a serious long-term threat to the species. In lieu of grazing withdrawals, management plans for Stanleya populations should take into account the biennial reproductive cycle of the species. Plants appear to be generally unpalatable to domestic stock (although plants are occasionally chewed on), so it is probably more critical to avoid impacting populations by trampling during their pre-reproductive (i.e. non-flowering) phase, to promote the survival of high quality second year plants which can then bolt, flower, and contribute to the soil seed bank. <br>

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Reference Code: U08MEI01IDUS <br>

Full Citation: Meinke, Robert J. 2008. Conservation Ecology and Life History Observations for the Malheur Prince’s Plume (Stanleya confertiflora: Brassicaceae): 2007 Demographic Field Work Summary. Prepared in Collaboration with the Burns and Vale BLM Districts. Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR <br>

Location: ELECTRONIC FILE - BOTANY: PLANT SPECIES: { Stanleya confertiflora } <br>

Keywords: Stanleya confertiflora, Malheur Prince’s Plume, conservation assessment, status assessment, Oregon, Idaho, field season, field study,monitoring, precipitation, life history, population dynamics <br>