Mapping and Assessment of Idaho phlox (Phlox idahonis) Populations II: All occurrences

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Abstract:

Idaho phlox (Clearwater phlox, Phlox idahonis) is a rhizomatous, perennial herb endemic to Clearwater County, Idaho, where it occupies montane wet meadows. The Idaho Natural Heritage Program recognizes eight separate population centers (occurrences). Its habitat has been reduced by road and railroad construction, livestock grazing, and land development. More than 95% of the area on which it is known to occur is owned by Potlatch Forest Holdings, Inc. (PFH), a real estate investment trust. A Conservation Agreement between PFH and the US Fish and Wildlife Service (USFWS) is pending for this species. Recommendations in the draft agreement include accurate mapping of existing populations. This report documents field work conducted from 2008 to 2010 during which the eight known populations of Idaho phlox were mapped using global positioning system (GPS) technology, which had not been used in previous surveys for Idaho phlox. Mapping was conducted by two botanists, on foot, using hand-held GPS units, and was done between 17 June and 13 July while Idaho phlox was flowering. Standard Heritage Program data were collected for the first time since 2000, documenting associated species and assessing threats. <br> Digital data, collected in the field, significantly refined the representation of Idaho phlox distribution in the Idaho Natural Heritage Program’s spatial database. Three occurrences were extended slightly. Over all eight occurrences, about 40 ac were occupied by Idaho phlox. <br> In two occurrences, exotics were identified as a threat to Idaho phlox and its habitat. In addition, the exotic pasture grass Kentucky bluegrass (Poa pratensis) was a ubiquitous associate, although its effect on growth and reproduction of Idaho phlox is unknown. Recent logging had occurred in occupied habitat. <br> Idaho phlox appears to spread vigorously by rhizomes, making it impossible to identify genets or to count ramets on a subpopulation scale. We suggest that subpopulations be used as a unit of monitoring at a coarse scale and that long-term monitoring plots continue to be used for fine-scale monitoring. A separation distance of 100 m was adapted for defining subpopulations within an occurrence, resulting in a total of 25 subpopulations, varying in size from 14 ac to <4 m2. The rarity of Idaho phlox and the potential threats posed by weed invasion or land development indicate that further surveys and monitoring are warranted, as specified in the draft Conservation Agreement. <br>

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Reference Code: U13LIC01IDUS <br>

Full Citation: Lichthardt, J. and K. Gray. 2013. Mapping and Assessment of Idaho phlox (Phlox idahonis) Populations II: All occurrences. Idaho Department of Fish and Game, Idaho Natural Heritage Program, Boise, ID. 26 pp. plus appendices<br>

Location: ELECTRONIC FILE - BOTANY: PLANT SPECIES: { Phlox idahonis } <br>

Keywords: Phlox idahonis, Idaho phlox, Clearwater phlox, GPS, plant populations, rare plant survey, rare plant conservation, meadows <br>