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Soil moisture is a key limiting resource in arid and semi-arid environments for woody shrub species. We assessed if three arid communities differed in their level of dry season soil moisture content and if the dominant species in these communities differed in their ability to use soil moisture. Water potential of all of the dominant woody plant species occurring in chaparral, coastal sage, and Mojave Desert communities and soil moisture content of these sites were measured seasonally. Species occurring in the Mojave Desert exhibited the most negative water potentials while the coastal sage community displayed the least negative water potentials. Dry season volumetric soil moisture content of the Mojave Desert site was lowest (7%), the chaparral site was intermediate (10%), and the coastal sage scrub site had the moistest dry season soil (20%). These moisture differences developed even though the coastal sage and chaparral communities both received the same annual rainfall and had similar soil characteristics. Of the three communities, the coastal sage community may be particularly susceptible to invasion by woody shrub species because its soil moisture content would allow for germination and persistence of a wider range of potential invaders. Current differences among sites in numbers of non-native woody species are consistent with predicted differences in susceptibility to non-native species based on community water use and dry seasonal soil moisture.
Todsen's pennyroyal (Hedeoma todsenii R. S. Irving, Lamiaceae) is a federally endangered species from the mountains of south central New Mexico that rarely produces seed. In vitro propagation methods were developed to provide material for cryostorage and for reintroduction, if that becomes necessary. Cultures were initiated from shoot tips taken from the ex situ collection at The Arboretum at Flagstaff, resulting in 12 genetic lines that were maintained on MS medium with 0.1 mg/L BAP and 0.01 mg/L NAA. Tests with other media commonly in use in CREW's Endangered Plant Propagation Program indicated that MS medium with 0.5 mg/L BAP increased shoot production and MS medium with 0.5 mg/L IBA increased root production over the maintenance medium. Other concentrations of IBA tested did not improve rooting, and a pulse of IBA followed by culture on charcoal-containing medium did not increase rooting significantly above the control. Approximately half of the plants moved to soil survived acclimatization, regardless of previous treatments. Survival through cryopreservation averaged 35% with no significant difference between the encapsulation dehydration and encapsulation vitrification procedures, and shoot tips from all 12 lines have been banked in liquid nitrogen for long-term storage. RAPD analyses indicated that there was less diversity among plants that exist in close proximity in situ than among genotypes that are separated by more distance. These propagation, cryopreservation, and genetic analysis protocols are all methods that can be used as tools to provide support for the long-term conservation of this species.
Hazardia orcuttii (A. Gray) Greene is a 5–10 dm tall perennial shrub that is native to coastal sage scrub communities of southern California and northern Baja California. This species was listed as threatened by the California Department of Fish and Game in 2002 and is a federal candidate species, and the only known population in the U.S. is on a 1.6 ha mesa located in Encinitas, California. Very little is known about the general ecology of this species, thus, the goal of this research was to characterize the basic soil physical and chemical properties and plant community characteristics associated with this species. Research was conducted between January 2004 and July 2005 in 12.56 m2 randomly-located plots that either contained or lacked H. orcuttii. Soil in plots containing H. orcuttii had significantly higher clay, soil organic matter, total N, and soil moisture content than plots lacking H. orcuttii, while plots lacking H. orcuttii had significantly more surface litter content. Significant differences were also observed in plant species abundance between plots containing and lacking H. orcuttii, indicating fundamental differences in plant community composition associated with patches of H. orcuttii. Our data support the notion that H. orcuttii is a soil endemic; however, it is unclear whether H. orcuttii prefers soil richer in clay or is restricted to these soils because of other factors. Given the restricted nature of H. orcuttii, and the proximity of the extant population to residential areas, habitat protection from human degradation and fire should be a high priority.
Sclerophyll shrubs such as Arctostaphyllos viscida Parry (Ericaceae; whiteleaf manzanita) are often considered obstacles to afforestation. The establishment of conifer plantations in southwest Oregon presents challenging problems for initial seedling survival and subsequent growth. This region is characterized by hot dry summers, cool moist winters, and rocky, shallow soils at low elevations. The growth of competing hardwoods within conifer plantations creates the traditional problem of undesirable competition for the silviculturist. Accumulation of manzanita biomass also contributes heavily to fire hazard while at the same time providing biomass of potential value as biofuel. This study describes productivity of whiteleaf manzanita stands of varying density growing within the confines of Pinus ponderosa Dougl. ex C. Lawson var. ponderosa (Pinaceae; ponderosa pine) plantations of the same age on poor sites. We explore the ability of this shrub to generate biomass as a potential energy source. Growth prediction equations are for height, basal diameter, biomass per individual, and biomass per hectare by stand density. The accumulated biomass after 14 yr of growth ranges around 43 metric tons/ha, and represents a strong negative influence on the supposed productivity of interplanted pines of the same age. Energy content of biomass amounts to an accumulation rate of 1.6 × 106 megajoules/ha/yr on such sites, indicating a large biofuel potential by age 14 or more. Harvesting the manzanita will also provide a potential benefit to productivity of the pines.
Pine Hill lies near the center of a gabbrodiorite intrusion in the foothills of the Sierra Nevada mountain range in El Dorado County, CA, USA. We assembled an extensive flora, examined the distribution and associations of vascular plant taxa, and specifically focused on associations of six rare plant taxa. The influence of environmental variables on plant distribution was investigated using a stratified random plot sampling technique and applying canonical correspondence analyses. The site contained over 10% (741 plants) of the flora of the entire state of California including seven rare species. Species segregated into chaparral, oak woodland, and grassland communities. In chaparral and woodland, and on serpentine sites, over 75% of the flora was comprised of native species. The non-serpentine grassland community was dominated by exotic species (64% exotic) and contained no rare species. Shrub and tree cover were the most important biotic factors associated with plant species distribution; serpentine substrate, soil texture, elevation, and degree of disturbance were the most important abiotic factors. Five rare species were restricted to gabbro soils. Consideration of beta diversity contributed little to our understanding of vegetation patterns. Our analyses identified two types of chaparral which we termed “Xeric Seeding” and “Mesic Resprouting” to reflect the environmental conditions and the fire regeneration strategy of the vegetation. Each chaparral type contained different rare species whose regeneration strategies were concordant with chaparral regeneration type.
The combination Carex scirpoidea Michx. var. gigas Holm was published in 1904, without reference to a collector or specimen, citing only the type locality: Mt. Eddy, Siskiyou County, California. The first reference to a specimen as the type was in 1922 by Mackenzie, who cited a collection made by Cyrus Pringle in 1881, from Siskiyou Co., California. What constitutes the type of this combination has been questioned, however, and as late as 1999 was called unknown. A specimen has been found that bears every indication of being the holotype studied by Holm, collected on Mt. Eddy by E. B. Copeland in 1903.
Juncus marginatus is native in eastern North America, west to Arizona. Recent California treatments considered it a native species, and rare. Its collection history in Oregon and California was examined to determine if those populations are native or introduced. The earliest Oregon records are 1991 from disturbed sites. The earliest Calfornia records are from disturbed mining sites in 1965 and 1971. At least one California population is associated with exotic cranberry, Vaccinium macrocarpon, a documented vector for transport of propagules of wetland species native to eastern North America. Eight other Juncus species native to eastern North America are naturalized in the Pacific States, lending support to introduced status for J. marginatus in California. Subsequent discoveries of J. marginatus in Oregon and California suggest the species is expanding its adventive range into less disturbed plant communities.
Sidalcea gigantea G. Clifton, R. E. Buck, & S. R. Hill is described as a new species from the northwestern slope of the Sierra Nevada in Butte, Plumas, Sierra, and Yuba Counties and from the extreme southern Cascade Range in Shasta County, California. The new species is a robust, long-lived perennial from large and extensive rhizomes; it is one of the tallest species known in the genus and it forms the largest known clonal colonies. Based on both morphological and DNA characters, S. gigantea appears to be most closely related to S. asprella Greene and S. celata (Jeps.) S. R. Hill, both found in the vicinity of the new species. Sidalcea gigantea occurs around margins of meadows, seeps, and streams in montane conifer forests, especially Mixed Conifer Forest.