Alien and Rare Plant Inventory and Vegetation Mapping Garden Creek Ranch, Craig Mountain, Idaho 1996-1999 Summary Report (DIGITAL UPGRADE)

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This report summarizes the results of a 3-year botanical inventory and mapping of rare plants, plant communities and infestations of alien plant species at the Garden Creek Ranch, Craig Mountain, Idaho. Field work was conducted during the summers of 1996, 1997 and 1998. This was a cooperative project with the Cottonwood District, Bureau of Land Management, through the Challenge Cost-share Program and the Katharine Ordway/Rodney Johnson Stewardship Endowment. Potential habitat for two rare plants, Spalding’s silene and Palouse goldenweed, was identified during this survey and provided the basis for more intensive survey work in the China Garden Creek drainage, a cost-share project between The Nature Conservancy and the U.S. Fish and Wildlife Service conducted during the summers of 1997 and 1998. Additional rare plant and weed infestation information from this project is included in this report. <br>

Approximately 20% of the 13,945-acre Garden Creek Ranch was surveyed. Plant communities were sampled at combinations of eight different aspects and 3 different elevational ranges. Data obtained from sampling was used to predict plant communities at similar aspects and elevations, and vegetation was mapped for the entire Ranch. <br>

Forty-two different plant communities were identified on the Garden Creek Ranch during the survey, including 15 grassland types, 9 shrubland types, 6 coniferous forest types, and 12 riparian types. Seven of these plant communities are listed as elements of conservation concern by the Conservation Data Center (CDC). Canyon Grassland, a division of the Pacific Northwest Bunchgrass Biome, is the predominant vegetation type on the Ranch, comprising 63% of the area. Approximately one-half of the Canyon Grasslands consists of grassland community types within the bluebunch wheatgrass series and one-half consists of grassland community types within the Idaho fescue series. The remaining area consists of 16% cliffs, rock outcrops, or talus, 10% shrublands, 9% coniferous forest, and 2% riparian vegetation. <br>

All known occurrences of rare plants at the Garden Creek Ranch were mapped, including previously recorded occurrences and new occurrences identified during the survey. Conservation Data Center’s Rare Plant Observation Forms were completed for any new populations identified. Thirteen rare plants are known to occur on the Ranch. Many new populations of eight rare plants known to occur on the Ranch prior to the survey were located during the survey and include 1) green-band mariposa lily (Calochortus macrocarpus var. maculosus), 2) broad-fruit mariposa lily (C. nitidus), 3) dwarf gray rabbitbrush (Chrysothamnus nauseosus ssp. nanus), 4) Idaho hawksbeard (Crepis bakeri ssp. idahoensis), 5) Palouse goldenweed (Haplopappus liatriformis), 6) fern-leaf desert parsley (Lomatium dissectum var. dissectum), 7) Spalding’s silene (Silene spaldingii), and 8) purple thick-leaf thelypody (Thelypodium laciniatum var. streptanthoides). Spalding’s silene is currently being reviewed for potential listing as threatened or endangered by the U.S. Fish and Wildlife Service. Populations of five rare plants not previously known to occur on the Ranch prior to the survey were located during the survey and include: 1) stalk-leaved monkeyflower (Mimulus patulus), 2) Hall’s orthotrichum (Orthotrichum hallii), 3) goldback fern (Pentagramma triangularis ssp. triangularis), 4) Wolf’s currant (Ribes wolfii), and western ladies’ tresses (Spiranthes porrifolia). The occurrence of western ladies’ tresses is the first recorded occurrence in the state of Idaho. <br>

During the survey, observations regarding Palouse thistle (Cirsium brevifolium) prompted its addition to the CDC’s Review listing in the spring of 1999. Although noted at a number of sites on the Ranch during this survey, its presence was uncommon. Also, the majority of the Palouse thistle plants observed appeared to be significantly threatened by a biological control insect for musk thistle, Rhinocyllus conicus, which was laying eggs on the seed heads of the Palouse thistle. <br>

All infestations of a number of aggressive alien plant species encountered during the survey at the Garden Creek Ranch were mapped, including whitetop (Cardaria chalapensis), spotted knapweed (Centaurea maculosa), Russian knapweed (C. repens), yellow starthistle (C. solstitialis), common crupina (Crupina vulgaris), Canada thistle (Cirsium arvense), leafy spurge (Euphorbia esula), sulfur cinquefoil (Potentilla recta), oxeye daisy (Chrysanthemum leucanthemum), and weedy slumps. Infestations of yellow starthistle and annual bromes are the most extensive of all weeds at the Ranch. There are also large infestations of whitetop in the Cave Gulch/Cougar Creeks Study Area. Although only 20% of the Ranch was actually surveyed, it was possible to map approximately 80-90% of the yellow starthistle infestations on the Ranch due to the distinctive coloration of this weed which enabled mapping from opposite hillsides. All other weeds were mapped as they were encountered within the 20% survey area. The majority of weed infestations occur within the grasslands. Approximately one-fourth of the grasslands are infested with weeds at the Ranch. <br>

Management recommendations focus on weed control, restoration/rehabilitation, research and monitoring and surveying. Priority weed control is recommended for weed-free/minimally infested areas, rare plant sites, satellite infestations, newcomer weed infestations, and roadways. <br>

Upper Corral Creek is recognized as a potential Research Natural Area (RNA) and Redemsky Flats and Wapshilla Ridge are recognized as potential Areas of Critical Environmental Concern (ACEC). <br>

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Reference Code: U20HIL02IDUS <br>

Full Citation: Hill, J.L. 2020. Alien and Rare Plant Inventory and Vegetation Mapping Garden Creek Ranch, Craig Mountain, Idaho 1996-1999 Summary Report (DIGITAL UPGRADE). Idaho Natural Heritage Program, Idaho Department of Fish and Game, Boise, Idaho. Pp. 131, plus appendices. <br>

Location: ELECTRONIC FILE - BOTANY: MULTIPLE SPECIES <br>

Keywords: Garden Creek Ranch, GCR, Craig Mountain, Idaho, The Nature Conservancy, Bureau of Land Management, Conservation Data Center, CDC, green-band mariposa lily, Calochortus macrocarpus var. maculosus, broad-fruit mariposa lily, Calochortus nitidus, dwarf gray rabbitbrush, Chrysothamnus nauseosus ssp. nanus, Idaho hawksbeard, Crepis bakeri ssp. idahoensis, Palouse goldenweed, Haplopappus liatriformis, fern-leaf desert parsley, Lomatium dissectum var. dissectum, Spalding’s silene, Silene spaldingii, purple thick-leaf thelypody, Thelypodium laciniatum var. streptanthoides, Palouse thistle, Cirsium brevifolium, musk thistle, Rhinocyllus conicus, whitetop, Cardaria chalapensis, spotted knapweed, Centaurea maculosa, Russian knapweed, Centaurea repens, yellow starthistle, Centaurea solstitialis, common crupina, Crupina vulgaris, Canada thistle, Cirsium arvense, leafy spurge, Euphorbia esula, sulfur cinquefoil, Potentilla recta, oxeye daisy, Chrysanthemum leucanthemum <br>