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Home Land Upland Species and Communities

Galena Creek Rockcress (Arabis rigidissima var. demota)

Status and Trend

Interpretation and Commentary

GALENA CREEK ROCKCRESS


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Status: Unknown
Trend: Unknown
Confidence: N/A

 

  • Relevance - Galena Creek rockcress (Arabis rigidissima var. demota) is a slender perennial plant in the Brassicaceae (Mustard) family. The species has small white flowers and occurs in forest openings above 7,000 feet on moderate to steep slopes,often in drainage ways, near meadow edges, or in other moisture-accumulating microsites (Tiehm 1989). The species was first described in 1983, but itis very difficult to identify, and it appears to be hybridizing with the common Pioneer rockcress (Arabis platysperma) (Rollins 1983; Rollins 1993). The two species are quite similar, and while Galena Creek rockcress is taller, more erect in stature, and has more slender fruits than Pioneer rockcress, consistently distinguishing between these species and the hybrid is problematic (Engelhardt and Gross 2011a).Galena Creek rockcress has been found in the Tahoe Basin near Martis Peak and Incline Lake in the north, and near Monument Peak in the south (see map above).However, Pioneer rockcress is also very common in these areas, and hybridization appears to be an increasing problem. Galena Creek rockcress was first recommended for inclusion TRPA listed sensitive plant species in the 2001 Threshold Evaluation, based on the fact that it was identified as a focal species in the Lake Tahoe Watershed Assessment, and the U.S. Forest Service had listed it as a Species of Concern (Murphy and Knopp 2000; TRPA 2001).However, TRPA staff declined to evaluate the species in the 2006 Threshold Evaluation, citing concerns over the validity of the species, and a lack of information (TRPA 2007c). The speciesis on list 1B.2 of the California Native Plant Society, meaning it is “fairly endangered in California” (CNPS 2010), but the species is not recognized in the current edition of the Jepson Manual, the foremost authority on California flora (Hickman 1993; JEPSON 2011).
  • Adopted Standards  - Maintain seven Galena Creek rockcress population sites
  • Indicator - The total number of population sites that are maintained as suitable habitat as determined by a qualified expert.
  • Status – Presence/absence data is the most reliable type of data that may be collected for this species due to the difficulties with identification. In the first year of monitoring in 2004, Galena Creek rockcress was present, but the identity as Galena Creek rockcress was unconfirmed at 11 population sites (see above figure). In the following year, six new sites were added, also unconfirmed. Surveys were not conducted again until 2009, when no plants were observed at three population sites near Monument Peak. In 2010, specimens of Galena Creek rockcress were collected at five population sites (three near Incline Lake, and two near Martis Peak), and the status was unknown at the other nine population sites. The identity of specimens from the five population sites has not been confirmed by an expert and therefore, there was insufficient information to assess threshold attainment. Because of the uncertainty associated with the identification of the species, the current status was determined to be “unknown.”
  • Trend – As of 2010, surveys conducted by the U.S. Forest Service have identified Galena Creek rockcress at 14 potential population sites (Engelhardt and Gross 2011a). Of these 14 sites, the identity of collected specimens from five population sites near Martis Peak and Incline Lake need to be confirmed by an expert, and the status of nine population sites near Monument Peak is currently “unknown.” Therefore, it was not possible to determine a trend due to insufficient data.

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  • Confidence  - Because of uncertainty associated with status and trend (due to the difficulties associated with species identification and the incompleteness of the surveys), determination for confidence is “not applicable” (N/A).
  • Human and Environmental Drivers - Human activities that pose direct threats include recreational activities that might trample or uproot plants (e.g., camping, hiking, equestrian use, trail construction, snowmobiles).The Galena Creek rockcress population sites in the Monument Peak area occur within Heavenly Ski Resort, where construction and maintenance of ski facilities have the potential to directly impact entire population sites (Engelhardt and Gross 2011a). As with other high elevation species, changes in precipitation type, timing, and quantity associated with climate change may adversely affect the species by altering plant community composition and species interactions, and/or decoupling plant flowering periods and insect pollinator visitation.
  • Monitoring Approach – This species is included in the Sensitive Species Monitoring Program at the U.S. Forest Service - LTBMU.Plant population sites are visited every five years or more frequently when the occurrence is new or data suggests that the population is decreasing.
  • Monitoring Partners – Monitoring is conducted by botany staff from the U.S. Forest Service – LTBMU.

Links

 
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Map

Approximate locations of suspected Galena Creek rockcress in the Lake Tahoe Basin, September, 2010. Source: USFS-LTBMU

 

Trend Charts

Chart data not available at this time.
Number of population sites of Galena Creek rockcress where plants were present, absent, or where new population sites were detected between 2004 and 2009. Source: U.S. Forest Service-LTBMU.

Additional Info

References

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Additional Information

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  3. Conceptual Model:
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Last Updated on Tuesday, 13 November 2012 11:51