The following Participating Institutions are custodians for this species in the CPC National Collection:
Rae Selling Berry Seed Bank & Plant Conservation Programs
The conservation of Mentzelia mollis is fully sponsored.
Edward Guerrant, Ph.D. contributed to this Plant Profile.
The last extensive search for Mentzelia mollis (Smithman 1989) yielded good news: botanists found high population numbers. However, because it is an annual, it is susceptible to dramatic population fluctuations. For instance, the spring of 2001 was extremely dry and few, if any seedlings emerged that year (Findley 2001a). Depending on the viability of the soil seed bank, several years of low rainfall could be extremely detrimental to the population's long-term survival.
In an effort to protect this rare plant from destruction, an enclosure was erected around a large population of Bureau of Land Management (BLM) land to exclude cattle, off-road-vehicles, and hikers. Signs were posted requesting that the exclosure not be entered due to the unusual soils and rare plants, and informational brochures were placed in a box along the fence. As is often the case when protecting rare species, publicity can be a double- or even triple-edged sword. For those who are interested in the environment and in protecting it, the publicity surrounding a rare or endangered species invites learning and discovery. Publicity may also attract the attention of curious people who may, inadvertently, cause harm to the very plants they are interested in. In the case of Mentzelia mollis, it is common to see human footprints in the fragile "popcorn clay" within the enclosure. Perhaps they are merely curious, but their curiosity can be damaging to these rare plants, especially in years of low rainfall. On the more sinister side, publicity of rare and endangered species can draw unwanted attention and bring out the worst in people. Unscrupulous plant collectors may remove rare plants to sell or for their private collections. Others, who may be frustrated with the limitations and regulations enacted to protect the endangered species in general, may willfully destroy them. In the case of M. mollis, just three years after the construction of the enclosure, all but a few fence posts were removed, and the following year, all the wires were cut. On three separate occasions, signs on either end of the exclosure have been cut off or completely removed. The box containing brochures has been repeatedly filled with rocks or even stolen (Findley 2001b).
Researchers and land managers must walk a fine line between protecting a rare and endangered plant and educating the public.
Distribution & Occurrence
Grows only on dry, open, nearly barren soil comprised of clay and volcanic ash deposits with high potassium content. One type of soil is gray to green "montmorillonite," which is a puffy, powdery clay what becomes extremely slick and greasy when wet. The soil may be classified as fragile "popcorn clay." Elevations range from 4360 to 5250 ft (1329-1600m). There are few other species that grow these barren substrates. Those that do include Clomella macbrideana, Phacelia lutea, Monolepis pusila, Mentzelia albiclis, and Phacelia humilis. Average temperatures in Oregon habitats range from 23F (-5C) in January to 71F (22C) in July while summer daytime temperatures may remain above 87F (32C) for six weeks. Only 10 to 12 in (25 to 30 cm) of precipitation falls annually, most between October and April.
OR: Owyhee Uplands, Vale District BLM,
NV: Humboldt County
|Because Mentzelia mollis is an annual, population numbers will vary year to year as a result of yearly precipitation levels and temperatures. As of 1989: Estimated 30 populations in SE Oregon and SW Idaho, ranging from 15 individuals to over 10,000 (average around 1000-2000) (Smithman 1989). As of 1994, 2 known sites in Nevada with a total estimated 450 individuals (NNHP 2001).|
Conservation, Ecology & Research
Glad (1975) suspects that Mentzelia mollis can extract water from the crystalline structure of the clay particles of the Succor Creek formation. The soil is able to absorb great quantities of moisture when it rains.
The leaves of Mentzelia mollis are covered with bristly hairs, which sticks to animals and humans like "living Velcro." Wildlife trails connect ash beds and animal mediated transport may the primary means of long distance dispersal of seed. Many populations are within view of each other. Seedlings also establish at base of ashy knolls as seeds roll down the hill (Smithman 1989).
Bumblebees appear to be the primary pollinator. Flowers begin opening at about 1 p.m. and all flowers are fully open by about 2:30 p.m. Flowers close shortly after sunset. They receive most of their visitors from about two hours before sunset until it is nearly dark (Glad 1975).
The healthiest stands of Mentzelia mollis are on ash beds surrounded by native vegetation (Smithman 1989). Yellow star thistle, an aggressive and noxious weed, is invading the nearby area. Aggressive treatments are being applied, which are largely effective in holding it at bay. Although no yellow star thistle has been found on ash sites containing M. mollis, it is presumed that the thistle will be able to colonize the area (Findley 2001b).
Trampling by cattle and hikers. Cattle do occasionally eat the plants, but they are prickly and probably not very palatable (Findley 2001b).
Climatic fluctuations (droughts esp.) if population levels low (
1) The germination requirements of Mentzelia mollis seeds in native soil. Results suggest that M. mollis requires at least 3 months of cold, moist stratification. The species may rely heavily on late fall and early winter rains to soak the clay in which they grow.
2) The correlation of Mentzelia mollis presence with soil clay content. The peak distribution of M. mollis corresponds to about 30% clay content.
3) Preliminary studies on mineral content of soils in which M. mollis grows. No unique mineral tolerance has been identified as of yet. Additional metals and compounds should be examined to make a final determination (Mansfield, 2001).
Germination studies at The Berry Botanic Garden resulted in little germination. Apparently good seeds were subjected to either 8 weeks of cold stratification or no cold stratification, followed by constant 68F (20C) or alternating 50F/68F (10C/20C) temperatures. 20% germination was achieved with cold stratification and alternating temperatures. No other seeds geminated (BBG File).
Most sites are open to livestock grazing (Findley 2001b).
Seeds from 1 site in Idaho and 5 sites in Oregon are stored at The Berry Botanic Garden.
Listed as Endangered by the state of Oregon.
Conduct photo-monitoring as trampling by researches poses a great threat to the delicate substrate (Findley 2001b).
Classify land as Areas of Critical Environmental Concern (ACEC) to protect it from further damage (Smithman 1989).
Construct exclosures to protect Mentzelia mollis habitat from destruction (Smithman 1989).
Experimentation with revegetation on selected disturbed sites (Smithman 1989).
Determine pollen to ovule ratios to assess whether inbreeding or outcrossing is more common (Smithman 1989).
Study reproductive processes and seed dispersal (Smithman 1989).
Conduct a morphological comparison of northern and southern populations (Smithman 1989).
Analysis of genetic variation within and among populations and number of "individuals" in and between populations could aid in management (Smithman 1989).
Determine longevity of seeds in soil seed bank.
Determine optimal germination requirements.
Determine effective and economical reintroduction protocols.
Meinke, R.J. 1982. Threatened and Endangered Vascular Plants of Oregon: An Illustrated Guide. Portland, Oregon: U.S. Fish & Wildlife Service, Region 1. 326p.