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The paper reviews published botanical and pedological literature concerning gabbro in the California Floristic Province. Gabbro is a mafic plutonic rock that is common in the Sierra Nevada, Klamath Mountains, and Peninsular Ranges of the California Floristic Province. Its mineralogical and chemical compositions span the range between those of peridotite, an ultramafic rock, and diorite, a rock more silicic than gabbro. A broad range of nutrient element compositions makes gabbro soils extremely diverse substrates that harbor numerous rare and endemic plant species, particularly at the Pine Hill intrusive complex in El Dorado County, California. Several directions for further work are also suggested. More research is required to discern the poorly understood factors affecting endemism and plant distributions on gabbro soils. Attention should be paid to floristic differences between olivine gabbro, which chemically borders serpentine, and gabbro lacking olivine or containing more hornblende than olivine. A species list is provided which highlights rare, serpentine-preferring, and gabbro-endemic taxa reported from gabbro soils in the California Floristic Province.
Mentzelia monoensis J. M. Brokaw & L. Hufford is a cryptic hexaploid species known only from Mono County, California. Previous studies have suggested a recent allopolyploid origin of M. monoensis but have not investigated the causes of its narrow distribution. Here we report the discovery of a unique haplotype from the chloroplast intergenic spacer ndhF-rpl32 that is sufficient to distinguish M. monoensis from all other species in Mentzelia sect. Trachyphytum using preserved specimens from any developmental stage. Based on soils collected with verified voucher specimens, we show that the edaphic niche of M. monoensis is significantly different from those of all other species in Mentzelia sect. Trachyphytum. A principal components analysis suggests the edaphic niche of M. monoensis is also one of the most extreme in Mentzelia sect. Trachyphytum. Most populations of M. monoensis were collected in soils derived from silica-rich rhyolite tephra produced by the Mono Craters volcanic chain. These coarse textured soils are lower in cation exchange capacity and plant available nutrients than those of any other species in Trachyphytum. Our findings suggest that edaphic specialization may have played a significant role in the establishment and geographic distribution of M. monoensis and other species in the Mono Basin.
Vegetation structure, composition, and community patterns on the landscape of southwest Oregon have changed since Euro-American settlement began in the mid-1800s. Much of this change has been attributed to the transition of land management strategies from those dominated by Native American practices, through the early Euro-American settlement period, and on to the post World War II era of industrial scale timber harvest and fire suppression. Using homestead patent applications and associated land classification maps generated under the Forest Reserve Homestead Act of June 11, 1906, we add to the understanding of historic vegetation conditions and evaluate vegetation change over time for land applied for by homesteaders in the Applegate River watershed of southwest Oregon. These homesteads were predominately located on areas now supporting chaparral, Pinus and/or Quercus woodlands, mixed conifer forests, pastures, and agricultural land. Our study presents primary source documentation that describes stands dominated by broadleaf trees and shrubs as dense at the time of patent application, contrary to the assumption that such stand structures are an artifact of fire suppression efforts of the last century. Historic vegetation polygons cross tabulated with current classified imagery in GIS indicate that conifer forests and shrublands each retain most of their former extents within their same locations on the landscape. The persistence of shrub stands to current times implies longer-term stability of these communities and indicates that a transition to conifer domination is not evident in all shrublands.
Two of the most used sources for distributions of cacti (Cactaceae) indicate the family's northern range limit is either 58°N or 58°15′N for Opuntia fragilis. However these sources overstate the range limit by almost two degrees, an error that probably originated as a simple misreading of the latitude of Fort St. John. I discuss records of O. fragilis at and just south of 56°17′ N along the Peace River valley between Fort St. John, British Columbia and Peace River, Alberta, as well as why it is surprising but unlikely that specimens currently exist farther north. An error in latitude of 2° (223 km) in range can adversely affect ability to empirically estimate effects of climate change.
Three species in the genus Gemmabryum J.R. Spence & H.P. Ramsay are described and illustrated. Two species, G. brassicoides J.R. Spence & K.M. Kellman and G. vinosum J.R. Spence & K.M. Kellman, are new to science. The third species, G. californicum (Sull.) J.R. Spence, previously considered to be part of G. dichotomum (Hedw.) J.R. Spence & H.P. Ramsay, is re-instated as a full species due to its highly unusual bulbil morphology. Gemmabryum vinosum is distributed in California, Oregon, and Montana, while the other two species are endemic to California.