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Using Distance Sampling to Estimate Density and Abundance of Saussurea Weberi Hultén (Weber's Saw-Wort)

Schorr, Robert A.
The Southwestern naturalist 2013 v.58 no.3 pp. 378-383
Culicidae, Saussurea, all-terrain vehicles, climatic factors, habitats, pollinators, population size, Colorado, Montana, Rocky Mountain region, Wyoming
Saussurea weberi Hultén (Weber's saw-wort) is a rare alpine calciphilic plant of the Rocky Mountains with disjunct populations in Colorado, Wyoming, and Montana. In Colorado, populations of S. weberi are scattered among <20 locations within the Mosquito Range and Hoosier Ridge regions. Saussurea weberi has specific habitat requirements, and its populations or populations of its pollinators may be susceptible to changing climatic conditions and use of off-road vehicles. It is scarce and discontinuous throughout its range, and there is no reliable estimate of density or abundance. Most estimates of abundance are based on cursory visits and unreplicated counts. To quantify size of the population at one of its centers, I used distance-sampling techniques to sample the population at Horseshoe Cirque, Park County, Colorado. I estimated density and abundance and examined variability of estimates to provide information for understanding the size of populations and for guidance in future protocols for sampling.