Cup Lake Draba (Draba asterophora var. macrocarpa)
Cup Lake draba is a small alpine perennial plant in the Brassicaceae (mustard) family. The species has small yellow flowers and is characterized by a cushion growth form where all the foliage grows close to the ground in a short mound or mat. It is found above 8,200 feet in rocky subalpine coniferous forests. The distribution of Cup Lake draba is extremely limited with only two known populations in the Desolation Wilderness. Cup Lake draba has a State Rank of S1 (critically imperiled), a Global Rank of G2T1 (critically imperiled), and a CNPS Rare Plant Rank of 1B.1 (rare, threatened, or endangered in California and elsewhere; seriously endangered in California). Human activities that pose direct threats include recreational activities that might trample or uproot plants (e.g., camping, hiking, equestrian use, trail construction, snowmobiles). However, the known populations are located in remote, off-trail areas, and potentially of greater concern is the threat of climate change. Cup Lake draba is monitored by the USDA Forest Service.
Status
A population is generally defined as occuring at least 1 km from another population, and a subpopulation is defined as a descrete occurence within 1 km of other subpopulations. According to this definition, Cup Lake Draba occurs in only two populations, at Saucer Lake and Cup Lake. However, because Cup Lake is outside of Tahoe Basin, it cannot be included in the threshold standard. The standard is to maintain a minimum of two Draba asterophora var. macrocarpa population sites.
Data provided by the U.S Forest Service.
2023 Evaluation
- Status
- Considerably Better Than Target
- Trend
- Little or No Change
- Confidence
- Moderate
Applicable Standard
VP19: Maintain a minimum of 2 Draba asterophora var. macrocarpa population sites.
Key Points
- Monitoring in 2019 and 2022 confirmed the presence of Cup Lake Draba at the long term monitoring sites and found two new subpopulations since 2015 monitoring was conducted.
- Eleven subpopulation sites is well above the standard of 2, but total population health within the region could be declining.
- Some subpopulations locations may have been affected by the Caldor Fire.
- Despite threats from climate change, the Tahoe Basin population of this species appear to be mostly healthy and stable.
- TRPA and partners have adopted ordinances, policies, and programs that require that sensitive plants be protected from adverse activities; projects must fully mitigate impacts to sensitive plants, or they will be prohibited.
About the Threshold
- Cup Lake draba (Draba asterophora var. macrocarpa) is a small alpine perennial plant in the Brassicaceae (mustard) family. The species has small yellow flowers and is characterized by a cushion growth form where all the foliage grows close to the ground in a short mound or mat (Baad 1979). Cup Lake draba occurs on steep, north-facing talus slopes, chutes and boulder slopes on decomposed granite soils (Hickman 1993). It is found above 8,200 feet in rocky subalpine coniferous forests (CNPS Rare Plant Program 2016). The distribution of Cup Lake draba is extremely limited with only two known populations in the Desolation Wilderness. One population is at Cup Lake on the El Dorado National Forest (outside of the Region), and the other occurs as multiple subpopulations along a ridge between Talking Mountain and Ralston Peak (within the Region). More than half of the known plants occur in the Tahoe Region population. Thus the Region population is critical to the viability of the entire species. Cup Lake draba has a State Rank of S1 (critically imperilled), a Global Rank of G2T1 (critically imperilled), and a CNPS Rare Plant Rank of 1B.1 (rare, threatened, or endangered in California and elsewhere; seriously endangered in California) (CNPS Rare Plant Program 2016).
- Human activities that pose direct threats include recreational activities that might trample or uproot plants (e.g., camping, hiking, equestrian use, trail construction, snowmobiles) (CNPS Rare Plant Program 2016). However, the known populations are located in remote, off-trail areas, and potentially of greater concern is the threat of climate change. Climate change may adversely affect Cup Lake draba populations through its influence on precipitation type, timing, and quantity. Decreased snowpack or a change in snowmelt timing could alter plant community composition and species interactions, and/or decouple plant flowering periods and insect pollinator visitation.
Rationale Details
- Considerably better than target. Cup Lake draba currently exists in 11 confirmed subpopulations found in surveys in 2019-2022. The current status is 550 percent of the threshold standard to maintain two population sites. The standard is in attainment and determined to be considerably better than target.
- Little or no change. In the most recent surveys (2022,2023) the 11 Cup Lake draba transects repeatedly monitored by the USDA Forest Service - Lake Tahoe Basin Management Unit were confirmed present. Some population sites may have been affected by the Caldor Fire in 2021. Survey results show variable trends within the subpopulations.
Confidence Details
- High. Long-term monitoring is conducted by USDA Forest Service botanists.
- Low. Data is likely too limited to make firm determination on trend. The majority of subpopulation sites were last visited in 2019. There are two main population sites, DRASM1b and DRASM1e, with variable trends between the sites. Declines were documented at the DRASM1b sites between 2015 and 2022. The DRASM1e site has seen less change, with population levels in 2022 and 2023 down from the 2015 peak, but above the numbers observed when long term monitoring plot was established in 2010.
- Moderate. If one confidence rating is high and the other is low, the overall confidence rating is moderate.
Additional Figures and Resources
No photos available.
- Uploaded On
- 11/25/2024
- File Type
- Description
- Long Term Monitoring Plan for Draba asterophora var. asterophora & Draba asterophora var. macrocarpa (Online Version: Sensitive plant locations omitted) USDA FOREST SERVICE ELDORADO NATIONAL FOREST, HUMBOLDT-TOIYABE NATIONAL