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    Author(s): Lee E. Hughes
    Date: 2001
    Source: In: Maschinski, Joyce; Holter, Louella, tech. eds. Southwestern rare and endangered plants: Proceedings of the Third Conference; 2000 September 25-28; Flagstaff, AZ. Proceedings RMRS-P-23. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. p. 78-82.
    Publication Series: Proceedings (P)
    Station: Rocky Mountain Research Station
    PDF: View PDF  (422.53 KB)

    Description

    Four listed plants on the Arizona Strip are being monitored for various population characteristics. Pediocactus sileri Engelm. L. Benson and P. bradyi L. Benson have been monitored since 1985-86, Asclepias welshii N & P Holmgren since 1989, and Cycladenia humilis Benth. var. jonesii Welsh & Atwood since 1993. The two pediocactus species were monitored in plots where each cactus was tagged, measured for height or width, and mapped; how many cactus fruited and the mortality rate were also noted. Asclepias welshii plants were counted and mapped, and each stem was checked for follicles. Seedlings were also noted. The Cycladenia humilis var. jonesii were counted and checked for follicles in two plots. The size structure of Pediocactus sileri has shown a strong shift to the smaller size class from the midsize class. Pediocactus bradyi has also shifted to the smaller individuals. The counts on the Cycladenia humilis var. jonesii and Asclepias welshii populations through the years have demonstrated ups and downs in population numbers, probably in line with precipitation amounts. Management plans have been implemented for the two pediocactus species to deal with the threats listed for the species: livestock trampling, off-road vehicle activity, mineral activity, and collection. There is a recovery plan for the Asclepias welshii (Welsh's milkweed), but not for the cyclad.

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    Citation

    Hughes, Lee E. 2001. Monitoring update on four listed plants on the Arizona Strip. In: Maschinski, Joyce; Holter, Louella, tech. eds. Southwestern rare and endangered plants: Proceedings of the Third Conference; 2000 September 25-28; Flagstaff, AZ. Proceedings RMRS-P-23. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. p. 78-82.

    Keywords

    plant conservation, genetics, demography, reproductive biology, monitoring, endangered species

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https://www.fs.usda.gov/treesearch/pubs/41908