Monitoring Packard’s milkvetch (Astragalus cusickii var. packardiae) in Southwestern Idaho, 2013 results

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Packard’s milkvetch (Astragalus cusickii var. packardiae) is a perennial plant species endemic to sparsely vegetated sedimentary outcrops in northeastern Payette County, Idaho. It is one of the rarest plant species in the Idaho flora, and a Candidate species for possible listing under the Endangered Species Act. Documented threats at multiple Packard’s milkvetch locations include wildfire, invasive grass species, off-road motorcycle hill climbing, and livestock tracking. A rangewide monitoring program for Packard’s milkvetch was initiated in 2008 to support pro-active and adaptive land management efforts related to the long-term conservation of the species and its habitat. Quantitative sampling at 21 permanently marked plots included the full complement of monitoring protocols each year from 2008 to 2012, but was limited to the collection to ground disturbance data and re-taking photo point photographs in 2013. Monitoring in 2013 marked the sixth consecutive year collecting ground disturbance information. <br> One or more ground disturbance factor was recorded at all monitoring transects in 2013. Total ground disturbance cover at individual transects ranged from <1% - 25%, with the rangewide mean of 6.3% being a lower value compared to previous monitoring years. Analysis showed no significant difference in the annual rangewide mean for total ground disturbance between the six monitoring years, nor did it detect a significant upward or downward trend for this attribute. Monitoring recorded a total of 7 motorcycle tracks at 4 plots in 2013. All represented old, remnant tracks pre-dating 2013, and likely 2012 as well. Mean rangewide motorcycle track ground cover disturbance was 0.1%, a value lower than any previous monitoring year. Analysis found the decrease in motorcycle track disturbance to be nearly significant, and did detect a significant downward trend in rangewide motorcycle track disturbance for the six year dataset. Livestock track-related disturbance was recorded at all transects, although some of this disturbance pre-dated 2013. Abundance at individual plots ranged from <1% – 6.4% ground cover. The rangewide mean of 2.1% was a value lower than any previous monitoring year. Analysis detected no significant difference in the annual rangewide mean for livestock-related track abundance between the six monitoring years; nor did it find a significant upward or downward trend for this attribute. Animal burrow disturbance occurred at 9 transects in 2013, and ranged from <1% - 25% ground cover. The rangewide mean of 2.8% was the highest value in six years of monitoring. Overall, animal burrowing accounted for 44% of all ground disturbance recorded on transects in 2013, and represented the first year livestock-related tracks were not the most abundant disturbance factor. <br> A pilot project to restore a buffer of shrub-steppe habitat at two Packard’s milkvetch subpopulations in the Bannister Basin area was initiated in 2012. Plots were established in 2012 and 2013 adjacent to the two subpopulations to monitor efficacy of the restoration treatments. At each location, one plot will be subject to restoration treatment, with the second plot being an untreated control. Vegetation sampling in 2013 found introduced grass species dominated the herbaceous component at each of the habitat restoration plots. Data collected in 2012 and 2013 occurred prior to any restoration treatment and provides the baseline against which post-treatment monitoring can be measured and compared in the future. <br> Monitoring information proved key in development of a Candidate Conservation Agreement for Packard’s milkvetch and will remain a vital management tool to help assess the effectiveness of conservation actions and also help provide rationale and guidance to future adaptive management measures.

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Reference Code: U14MAN03IDUS <br>

Full Citation: Mancuso, M. 2014. Monitoring Packard’s milkvetch (Astragalus cusickii var. packardiae) in Southwestern Idaho, 2013 results. Prepared for U.S. Fish and Wildlife Service, Boise, Idaho. Mancuso Botanical Services, Boise, Idaho. 26 pp, plus appedices <br>

Location: ELECTRONIC FILE - BOTANY: PLANT SPECIES: { Astragalus cusickii var. packardiae } <br>

Keywords: Packard’s milkvetch, Astragalus cusickii var. packardiae <br>