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Home Land Upland Species and Communities

Long-petaled Lewisia (Lewisia longipetala)

Status and Trend

Interpretation and Commentary

LONG-PETALED LEWISIA


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Status: Considerably Better Than Target
Trend: Little or No Change
Confidence: Moderate

 

  • Relevance - Long-petaled lewisia(Lewisia longipetala) is a low-growing perennial plant in the Purslane (Portulaceae) family. The species has pale pink flowers and fleshy leaves and grows on high elevation peaks (>8,000 feet) in moist, rocky habitats directly below persistent snowfields (Halford and Nowak 1996). The worldwide distribution of long-petaled lewisiais limited to the Sierra Nevada crest in El Dorado, Nevada, and Placer Counties, California (CNPS 2010). Within the Lake Tahoe Basin the species is found in the vicinity of three lakes in the Desolation Wilderness: Dicks Lake, Lost Lake, and Azure Lake (see above map). The current status of the majority of occurrences located outside of the Lake Tahoe Basin is unclear, but it is likely that the greatest number of plants occurs in the Basin populations, and therefore, these populations are critical to the viability of the entire species.Long-petaled lewisiahas special designations by TRPA and the U.S. Forest Service that provide the plants with increased levels of protection.
  • Adopted Standards  - Maintain two Long-petaled lewisiapopulation sites.
  • Indicator - The total number of population sites that are maintained as suitable habitat as determined by a qualified expert.
  • Attainment Status – Long-petaled lewisiacurrently exists in the Lake Tahoe Basin in the vicinity of three lakes in the Desolation Wilderness (Engelhardt and Gross 2011a).A combined total of eight population sites exist near these three lakes, indicating a trend determination of “considerably better than target.” Therefore, the Threshold Standard is in attainment.
  • Trend – Quantitative monitoring of long-petaled lewisiain the Basin began in 2004 when plants were located and counted at six population sites (Engelhardt and Gross 2011c). An additional site was added in 2006. All sites were re-surveyed in 2009. Between 2004/06 and 2009, plant counts at four of the seven populations sites were stable (57%), one increased (14%), and two declined (28%). A new population site in the vicinity of an existing site was also added, bringing the number of tracked population sites in the Tahoe Basin to eight. Recent declines in snowpack may have contributed to the decline of two of the four population sites at Dicks Lake (above figure), but successive years of data will be required to better assess the trend for long-petaled lewisia. Since plant counts at the majority of sites were stable, increased, or were newly identified, and the alpine habitat where long-petaled lewisiaoccurs is naturally stable, a conservative approach leads to the conclusion that there is “little or no change” in the trend of long-petaled lewisia.

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  • Confidence  - There is a high degree of confidence in the status due to the quality of the data collected and the robust nature of the monitoring program. However, there is low confidence in the trend analysis because it was based on data from only two sample periods in 2004/06 and 2009. Therefore, there is a “moderate” level of confidence in the status and trend.
  • 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) (Halford 1992).However, the known populations in the Basin are located in remote, off-trail areas; of greater concern is the potential threat of snowpack decline and altered hydrologic regimes related to climate change. Long-petaled lewisiapopulations are very dependent on water supplied by persistent snowfields, so changes in the timing and quantity of snowmelt associated with climate change have the potential to impact the species (Halford and Nowak 1996). Competitive exclusion could also occur if other plant species gain the ability to expand into habitat that previously supported hydrologic conditions more favorable for long-petaled lewisia (Halford and Nowak 1996).
  • Monitoring Approach – An extensive survey was conducted for long-petaled lewisia in 1991 and one long-term monitoring plot was installed at a population site occurring in the Basin (Halford 1992). More recently, the U.S. Forest Service initiated a comprehensive monitoring program forthe species in 2004 based on similar methods (Engelhardt and Gross 2011c). Long-term monitoring plots were installed at Dicks Lake and Lost Lake, but it was not possible to establish plots at Azure Lake due to the presence of extensive granite slabs that prevented the installation of permanent markers. Plant populations are visited every five years, or more frequently when data suggests the population is decreasing. The monitoring objective is to provide a quantitative and consistent method for evaluating status and trend, especially at sites comprised of large numbers of plants where it is difficult to accurately count individuals. Monitoring at permanent plots allows for more repeatable and efficient surveys.
  • Monitoring Partners – A long-term monitoring plan was developed and is implemented by ecology and botany staff from the U.S. Forest Service – LTBMU in coordination with Eldorado and Tahoe National Forest staff. Monitoring isbeing conducted at two locations within the Basin.

Links

 

Map

 

 

 

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Trend Charts

Chart data not available at this time.
Number of population sites of Long-petaled lewisia where plant counts decreased, increased, were stable, 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 12:04