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Leaf litter accumulation may negatively impact seedling germination by altering key ecosystem properties, such as light availability and soil moisture. The impacts of litter depth may be particularly strong for species in dry environments with low vegetative cover and high light availability. The rare species Boechera constancei (Rollins) Al-Shehbaz (Brassicaceae) is endemic to the serpentine outcrops of Plumas and Sierra Counties, where litter accumulation is highly variable and B. constancei inhabits a range of litter depths (0–40 mm). In this study, we tested whether increased litter depth impedes germination, and whether populations vary in tolerance to litter depth. Specifically, we quantified the impacts of treatments representing the observed range of litter depth occupied by B. constancei on the germination of seed collected from nine populations. Differences in germination were analyzed using a two-way ANOVA. While both source population and litter treatment influenced germination, the interaction term was not significant. Post-hoc Tukey's honest significance tests revealed that germination under both median and high litter treatments was significantly lower than under no litter. The median and high litter treatments did not differ significantly. Differences in germination were observed during dark, cold stratification, suggesting that light availability was not a factor. These results indicate that early life stages of this species may benefit from litter reduction treatments, as both median and high litter treatments reduced germination.
The Cottonwood Fire consumed about 185 square kilometers in the Tahoe and Toiyabe National Forests near Loyalton and Sierraville, CA in 1994. The wildfire reached a population of one of the rarest pines in North America, Pinus washoensis H.Mason & Stockw. (Washoe pine), in the Babbitt Peak Research Natural Area (RNA). A field survey and census was conducted in 1996 to find, map, and count living and dead P. washoensis individuals, and to assess the effects of the fire on the population. Although the fire reached most of the P. washoensis stands, 763 living reproductive individuals were found and less than 5.2% mortality was observed. The fire's intensity declined as it crossed the Bald Mountain ridge and mostly consumed understory vegetation and litter in the P. washoensis stands. The fire had the potential to devastate or eliminate this rare population, but instead, a combination of stochastic, vegetative, and topographic controls spared the P. washoensis stands and appears to have had beneficial effects for this population. All age classes of P. washoensis except seedlings were found in the Bald Mountain Range. The lack of seedlings is surprising because the two years between fire and survey had high precipitation. No sign of hybridization with other yellow pine species was evident. While it is promising that the stands of this rare pine survived the Cottonwood Fire, prospects for the continued persistence of this population are not good until there is a reproductive year that provides many recruits.
Astragalus tricarinatus A.Gray is a federally-listed short lived perennial herb endemic to southern California. Its primary habitat is along the ecotone of the Mojave and Colorado Deserts in the San Bernardino and Little San Bernardino Mountains between 390 and 1525 m. Discovery of this species' upland habitat has prompted research into the ecology of populations across its range, as the life history and threats may be different from those of the previously-known wash populations. Our study sought to further document A. tricarinatus distribution and abundance within its range, as well as quantify impacts to its growth and reproductive efforts associated with co-occurring native and invasive plant species. We mapped all known localities in our study area on aerial imagery then used this to visually recognize its typical edaphic habitat and identify new potential sites. Where A. tricarinatus was found, we established plots in which plant size, the number of reproductive structures, and microhabitat characteristics were recorded. Two new occurrences (defined here as >1 km away from known localities) were recorded within its existing range as well as a previously undocumented locality between two known occurrences containing an estimated 2600 plants. Most plants were found on south and east aspects, and on slopes ranging from 30–45°. We found that increases in invasive cover correlated with a decrease in production of reproductive structures. As a federally-listed species occurring in steep, remote habitats with few threats, these findings suggesting an association between invasive species presence and reduced reproductive structures should be further investigated experimentally, as they affect population dynamics and conservation of this species.
Chorizanthe aphanantha K.M.Nelson & D.J.Keil is described as a new species from serpentine soils in the Irish Hills portion of the San Luis Range of central-western San Luis Obispo County. It occurs in portions of San Luis Obispo's Irish Hills Natural Reserve, where it grows with several other rare, serpentine-endemic taxa. It is distinguished from C. breweri S.Watson, with which it co-occurs and may be confused (particularly as it ages), by its compact, rather than sprawling habit; the green rather than red color of its herbage at the time of flowering; its much smaller, white, monomorphic perianth lobes, rather than white to pink, dimorphic lobes; bracts with straight, ascending, rather than recurved spine tips; smaller and smooth rather than transversely corrugated mature involucres; and basal leaf blades that are glabrous to minutely strigose, thin, and ovate to elliptic (occasionally mucronate) with obscure veins, rather than thick, leathery, reniform, and apically notched to ±obcordate with pronounced veins. It differs from the recently described C. minutiflora R.Morgan, Steyer, & Reveal by its sparser and shorter pubescence, entire versus erose perianth lobes, nine rather than three stamens, ovate to elliptic rather than oblanceolate basal leaves, and flat rather than undulating leaf margins. It is distinguished from the morphologically similar C. procumbens Nutt. by its ovate to elliptic rather than oblong to oblanceolate leaf blades, its sparser and shorter pubescence, the presence of a narrow scarious margin on the involucral teeth, smaller flowers, and distinct rather than basally connate filaments. A key is provided that distinguishes C. aphanantha from other Chorizanthe species in the San Luis Range. It is currently known to grow in serpentine scrub and chaparral at elevations from 100 to 370 meters.
Carex bajacalifornica Zika is described from five populations in the mountains of northern Baja California, Mexico, in the Sierra de Juárez and Sierra de San Pedro Mártir. It is distinguished from Carex rossii Boott by its short inflorescence bract, abbreviated perigynium beak shorter than the stipe, and nerved perigynium faces. Carex cryptosperma Zika, D.S. Bell, and L.J. Gross is described from 12 populations in southern California, in the San Bernardino, San Gabriel, and San Jacinto Mountains. Carex cryptosperma differs from Carex xerophila Janeway & Zika in its relatively short perigynium stipe and relatively long perigynium beak. The new species are illustrated and mapped, and a key is presented to members of Carex sect. Acrocystis in the states of California and Baja California.