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    Author(s): James F. FowlerCarolyn Hull Sieg; Shaula Hedwall
    Date: 2015
    Source: Western North American Naturalist. 75(1): 70-77.
    Publication Series: Scientific Journal (JRNL)
    Station: Rocky Mountain Research Station
    PDF: View PDF  (213.57 KB)

    Description

    Population size and density estimates have traditionally been acceptable ways to track species’ response to changing environments; however, species' population centroid elevation has recently been an equally important metric. Packera franciscana (Greene) W.A. Weber and A. Love (Asteraceae; San Francisco Peaks ragwort) is a single mountain endemic plant found only in upper treeline and alpine talus habitats of the San Francisco Peaks in northern Arizona and is listed by the U.S. Fish and Wildlife Service as a Threatened species under the Endangered Species Act. We used 2 recreational trails, which pass through its elevational distribution in the Kachina Peaks Wilderness Area, as sampling transects to estimate population density and distribution because it was not possible to sample further from the trail due to loose volcanic talus and consequent disturbance of P. franciscana plants. Between-year comparisons of ramet density, population centroid elevations, and mid-September flowering or fruiting counts were not significantly different for the Humphrey’s Peak Trail in 2010-2011 or the Weatherford Trail from 2009 to 2013. Use of a zero-inflated negative binomial response variable distribution allowed statistical inference for both sampling hits and misses, which gives ecologists and land managers an additional method to monitor changes in distribution and abundance. Population density and elevation of the population centroid estimates for P. franciscana appear to be stable; therefore, the 5-year Weatherford Trail data set may be used as a baseline to track future plant migration on a fine spatiotemporal scale, an approach that could apply to other threatened alpine species.

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    Citation

    Fowler, James F.; Sieg, Carolyn Hull; Hedwall, Shaula. 2015. Baselines to detect population stability of the threatened alpine plant Packera franciscana (Asteraceae). Western North American Naturalist. 75(1): 70-77.

    Keywords

    Packera franciscana, Asteraceae, plant migration, population stability

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