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Review of: North American Terrestrial Vegetation. Michael G. Barbour and William Dwight Billings. Cambridge University Press; 1st ed edition (March 25, 1988). 448 pages. ISBN: 978-0521261982.
Review info: A Natural History of the Sonoran Desert. Edited by S. J. Phillips and P. W. Comus. 2000. Arizona-Sonora Desert Museum Press, Tucson AZ, and University of California Press, Berkeley CA. 628 pp. Cloth ISBN 0-520-22029-3 Paper ISBN 0-520-21980-5.
A 2.1-m core from Laguna de las Trancas, a marsh atop a landslide in northern Santa Cruz County, California, has yielded a pollen record for the period between about 30,000 B. P. and roughly 5000 B. P. Three pollen zones are recognized. The earliest is characterized by high frequencies of pine pollen and is correlated with a mid-Wisconsinan interstade of the mid-continent. The middle zone contains high frequencies of both pine and fir (Abies, probably A. grandis) pollen and is correlated with the last full glacial interval (upper Wisconsinan). The upper zone is dominated by redwood (Sequoia) pollen and represents latest Pleistocene to middle Holocene. The past few thousand years are not represented in the core....
Postfire resprouting by woody plants confers a marked advantage in rate of recovery over species that regenerate entirely from seed. However, the predictability of this advantage varies markedly between species, with some showing nearly 100% rootcrown survival and others often much lower. This study examined patterns of fire-caused mortality and tested the relative importance of fire severity and plant age between various shrubs and subshrubs characteristic of chaparral and sage scrub associations. Resprouting success varied from about 10% for Eriogonum fasciculatum to a high of 98% for Quercus berberidifolia. For most of the shrub species, skeletons of resprouting plants were significantly taller than those of...
There is value in understanding the past and how it has affected the present. Science focuses on empirical findings, and we know that our prior experiences and those of our predecessors play important roles in determining how we interpret the present. We learn from accomplishments and foibles of predecessors and appreciate the real life experiences we have gone through. In our studies of the genus Arctostaphylos Adans. we have been struck by the fascinating stories surrounding taxonomists who have played roles in the development of our current understanding of the group. In addition to providing insights, they sometimes provide humor and lessons on the value of competition versus collaboration. We offer this history...
Categories: Publication;
Types: Citation;
Tags: R 18000 (Olfaction); SW 2060 (Effects on water of human nonw
Although widespread throughout the interior foothills of central and northern California, Pinus sabiniana Dougl. has a disjunct distribution in the southern Sierra Nevada, where it is abundant in the Kern River and Tule River watersheds, but is absent from the Kaweah River watershed between 36° and 37°N. This gap in the pine's distribution has long intrigued botanists and ecologists and has elicited a number of hypotheses for this anomalous biogeographical pattern. Here we propose a new hypothesis that couples unique features of the southern Sierra Nevada topography with unique features of P. sabiniana's response to fire. This low elevation pine is widely distributed in grassland and chaparral, and where it occurs...
The California chaparral community has a rich flora of species with different mechanisms for cuing germination to postfire conditions. Here we report further germination experiments that elucidate the response of several widespread shrub species whose germination response was not clear and include other species from the Sierra Nevada, which have not previously been included in germination studies. The shrubs Adenostoma fasciculatum and Eriodictyon crassifolium and the postfire annualMentzelia dispersa exhibited highly significant germination in response to smoke treatments, with some enhanced germination in response to heating as well. The shrubs Fremontodendron californicum and Malacothamnus fremontii were stimulated...
Ceanothus bolensis S. Boyd & J. Keeley is a new species in the subgenus Cerastes from northwestern Baja California, Mexico. It is well represented at elevations above 1000 m on Cerro Bola, a basaltic peak approximately 35 km south of the U.S./Mexican border. It is characterized by small, obovate to oblanceolate, cupped, essentially glabrous leaves with sparsely toothed margins, pale blue flowers, and globose fruits lacking horns. Principal components analysis on morphological traits shows it to be distinct from other members of Cerastes which are distributed away from the coast in southern California and Baja California, Mexico. These phenetic comparisons also suggest that Ceanothus otayensis should not be subsumed...
VTM (Vegetation Type Map) plots comprise a huge data set on vegetation composition for many parts of California collected mostly between 1929 and 1935. Historical changes in vegetation have been inferred by sampling these areas many decades later and evaluating the changes in plant dominance. VTM plots can not be precisely relocated, and it has been assumed that errors resulting from this problem are inconsequential or can be eliminated by comparison with a composite of multiple contemporary plots. This study examines that assumption for southern California shrubland landscapes by comparing the differences in species composition between closely positioned VTM-sized plots. Comparing shrub species density in 400-m²...
Human expansion into the Mojave Desert is a significant threat to rare desert plants. While immediate habitat loss is often the greatest concern, rare plants situated near areas where soil surfaces experience frequent disturbance may be indirectly impacted when fine particulate dust accumulates on leaf surfaces. Remaining populations of the federally listed Astragalus jaegerianus (Lane Mountain milkvetch) occur on land open to expanding military activities and on adjacent public land with increasing recreational use. This study was initiated to determine whether dust accumulation could decrease the vigor and fitness of A. jaegerianus through reduced growth. Beginning in early May 2004, plants located on Bureau of...
Effects of up to three successive spring and fall burns on composition and biomass of the predominantly non-native grasslands of the southern Sierra Nevada foothills were evaluated. Fall and spring burning regimes increased the number and biomass of both alien and native forb species. No native grass species became established following the treatments. Thus, whereas the biomass of alien grass species can be reduced by repeated burning, they will be replaced by increases in both alien and native forbs. Changes seen following one or two burns (spring or fall) were not sustained following cessation of burning treatment.
Low elevation grasslands in California long have been dominated by Mediterranean grasses, but many areas still have large native forb populations. Alien forbs invade these grasslands, displacing both native and other alien species. Italian thistle is a noxious alien herb that has recently invaded these grasslands, including ungrazed blue oak (Quercus douglassii) and interior live oak (Quercus wislizenii) stands in Sequoia National Park. Here, Italian thistle tends to dominate under oaks and has the potential to substantially alter the foothill ecosystem by displacing native plants and acting as a ladder fuel that can carry fires into the oak canopy. We tested the effects of selectively reducing Italian thistle populations...
This study compares postfire regeneration and diversity patterns in fire-prone chaparral shrublands from mediterranean (California) and non-mediterranean-type climates (Arizona). Vegetation sampling was conducted in tenth hectare plots with nested subplots for the first two years after fire. Floras in the two regions were compared with Jaccard's Index and importance of families and genera compared with dominance-diversity curves. Although there were 44 families in common between the two regions, the dominant families differed; Poaceae and Fabaceae in Arizona and Hydrophyllaceae and Rosaceae in California. Dominance diversity curves indicated in the first year a more equable distribution of families in Arizona than...
Changes are made in the nomenclature of species and subspecies in the genus Arctostaphylos(Ericaceae). In this study, the focus is on species found in the coast ranges of California. Changes are made in A. nortensis from the area around the Oregon border with California, in the A. nevadensiscomplex in the North Coast Ranges, in the A. nummularia complex of the north to central coast, in the A. tomentosa complex of the central coast to the Channel Islands, and in the A. hookeri and A. pilosula complex of the central coast. Also discussed are other changes presented elsewhere that will affect the Arctostaphylos treatment in the next edition of the Jepson Manual.
Review of: The Biogeography of Fire in the San Bernardino Mountains of California--A Historical Study. By Richard A. Minnich. University of California Publications in Geography Volume 28, University of California Press, Berkeley. 120 pp. plus plates, soft cover.
The genus Arctostaphylos consists mostly of chaparral shrubs known by the common name manzanita, and one of the widest ranging of these is A. glandulosa Eastw., distributed from Baja California to Oregon. Particularly in the southern half of its range it exhibits complex patterns of morphological variation that have long presented taxonomic challenges. Phenetic analysis of morphological traits from over 1400 individuals from throughout the range were used to examine intra- and inter-population patterns of variation. Multivariate ordination and hierarchical cluster analysis were used to determine phenetic patterns linked with ecological and geographical distributions. These analyses suggest the hypothesis that this...
Peniocereus striatus (Brandegee) Buxb. (Cactaceae) is an endemic Sonoran Desert cactus that reaches its northern range limit in southwestern Arizona. One U.S. population occupies a small area of Organ Pipe Cactus National Monument near the U.S./Mexico international boundary, which has been monitored since 1939. An extensive survey conducted in 2002, covering 177 ha, resulted in the discovery of 88 new plants, in addition to the relocation of 57 plants found in previous surveys. Despite potential increases in population size and spatial distribution, mean plant height and number of basal stems has not significantly changed in recent years. Bud scars revealed that a majority of the population was sexually mature....
Morphological intermediates between Tamarix ramosissima or T. chinensis (saltcedars) and T. aphylla (athel) were found recently in three locations in the southwestern USA, and were assumed to be hybrids or a previously unreported species. We sequenced chloroplast and nuclear DNA from putative parental and hybrid morphotypes and hybrid status of morphological intermediates was supported. Chloroplast data suggest that the seed source for these hybrids is T. aphylla. Invasive T. aphylla genotypes found in Australia match those found in the USA. Seed was collected from one of the hybrids, and a low percentage of it was viable. This hybrid combination has not been previously reported in the USA or the native ranges of...
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