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The Mohave Desert region, California, a geographic, geologic, and hydrologic reconnaissance
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An estimated potentiometric surface of the Death Valley region, Nevada and California, developed using Geographic Information System and automated interpolation techniques
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Geographic distribution: Batrachoseps attenuatus (California slender salamander)
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Depth determination of the 2010 El Mayor‐Cucapah earthquake sequence (M ≥ 4.0)
The 2010 M W 7.2 El Mayor‐Cucapah earthquake ruptured a zone of ~120 km in length in northern Baja California. The geographic distribution of this earthquake sequence was well constrained by waveform relocation. The depth distribution, however, was poorly determined as it is near the edge of, or outside, the Southern California Seismic Network. Here we use two complementary methods to constrain the focal depths of moderate‐sized events ( M ≥ 4.0) in this sequence. We first determine the absolute earthquake depth by modeling the regional depth phases at high frequencies (~1 Hz). We mainly focus on Pn and its depth phases pPn and sPn , which arrive early at regional distance and are less contaminated by crustal multiples. To facilitate depth phase identification and to improve signal‐to‐noise ratio, we take advantage of the dense Southern California Seismic Network and use array analysis to align and stack Pn waveforms. For events without clear depth phases, we further determine their relative depths with respect to those with known depths using differential travel times of the Pn , direct P , and direct S phases recorded for event pairs. Focal depths of 93 out of 122 M ≥ 4.0 events are tightly constrained with absolute uncertainty of about 1 km. Aftershocks are clustered in the depth range of 3–10 km, suggesting a relatively shallow seismogenic zone, consistent with high surface heat flow in this region. Most aftershocks are located outside or near the lower terminus of coseismic high‐slip patches of the main shock, which may be governed by residual strains, local stress concentration, or postseismic slip.
Geochemical evidence for water‐rock interaction along the San Andreas and Garlock Faults of California
Mesozoic granitoid rocks adjacent to the San Andreas fault in central California have retained their radiogenic Ar for the last 70 m.y. but have, generally, the highest 18 O and H 2 O + contents and the lowest D contents of all the granitoid rocks in California. The geographical coincidence of the D, 18 O, and H 2 O + patterns with the present trace of the San Andreas fault leave little doubt that some kind of groundwater circulation system has operated in the vicinity of the fault in central California. Similar isotopic patterns exist in rocks along the Garlock fault. These water‐rock interactions probably took place at temperatures <200°C, although depth, extent, and timing are not resolved. Stable isotope compositions of rocks from many localities of the earth have provided unambiguous proof that meteoric waters have descended to depths at least as great as 8 to 10 km when a heat source such as a cooling pluton was present. Massive circulation of groundwater is common in the upper crust of tectonically active areas and may affect the frictional stress state along major faults. The geochemical evidence for extensive deep circulation of groundwater and the relatively high permeabilities for most rocks of the upper crust recently compiled by Brace (1980) argues against nearly lithostatic fluid pressures as an ambient condition of the upper crust. Groundwater circulation along the San Andreas provides an efficient mechanism for diffusing the heat flow anomaly that arises in heat transport calculations that are based on thermal conduction alone.
Living on the edge: Identifying demographic bottlenecks in an isolated sage-grouse population
The greater sage-grouse ( Centrocercus urophasianus : hereafter sage-grouse) population in Modoc County California is geographically isolated and contains a single lek (from 56 leks in the 1940s), despite significant efforts to increase the population through translocations and habitat improvement. Repeated wildfire within the landscape has led to an increase in invasive annual grasses and a decrease in sagebrush ( Artemisia sp.) cover in important nesting and brood-rearing habitat. We estimated survival for adult females, nests, and chicks and assessed biotic characteristics that may influence these survival estimates to identify factors that may be limiting population growth. We monitored 37 female sage-grouse marked with GPS PTTS, 39 nests, and 8 broods for 3 years (2019–2021). We measured vegetation characteristics for nests at the microsite and landscape scale to evaluate effects on daily nest survival (DNS). We used survival rates from all life stages to parameterize matrix models and estimate population growth rate. Mean nest success over 3 years was 29% (95% CI: 17.1–44.8) across a 29-day incubation period and DNS declined as the proportion of both medusahead Taeniatherum caput-medusae and Japanese brome Bromus japonicus around the nest increased. Across all three years, mean chick survival across a 54-day period was 44% (95% CI: 0.9–72.3) and mean annual survival for adult females was 29% (95% CI: 17.8–43.7). Our estimated vital rates were 45–55% lower than distribution-wide estimates and the projected population growth rate was strongly declining (0.411, 95% CI: 0.30–0.52). Our results suggested recent cover changes associated with wildfire on the study area may have had a detrimental effect on this population across all life stages, and if attention is not given to preventing the transition from sagebrush communities into invasive grasslands, this population and others in degraded landscapes may not persist.
Hierarchical spatial genetic structure in a distinct population segment of greater sage-grouse
Greater sage-grouse ( Centrocercus urophasianus ) within the Bi-State Management Zone (area along the border between Nevada and California) are geographically isolated on the southwestern edge of the species’ range. Previous research demonstrated that this population is genetically unique, with a high proportion of unique mitochondrial DNA (mtDNA) haplotypes and with significant differences in microsatellite allele frequencies compared to populations across the species’ range. As a result, this population was considered a distinct population segment (DPS) and was recently proposed for listing as threatened under the U.S. Endangered Species Act. A more comprehensive understanding of the boundaries of this genetically unique population (where the Bi-State population begins) and an examination of genetic structure within the Bi-State is needed to help guide effective management decisions. We collected DNA from eight sampling locales within the Bi-State (N = 181) and compared those samples to previously collected DNA from the two most proximal populations outside of the Bi-State DPS, generating mtDNA sequence data and amplifying 15 nuclear microsatellites. Both mtDNA and microsatellite analyses support the idea that the Bi-State DPS represents a genetically unique population, which has likely been separated for thousands of years. Seven mtDNA haplotypes were found exclusively in the Bi-State population and represented 73 % of individuals, while three haplotypes were shared with neighboring populations. In the microsatellite analyses both STRUCTURE and FCA separate the Bi-State from the neighboring populations. We also found genetic structure within the Bi-State as both types of data revealed differences between the northern and southern part of the Bi-State and there was evidence of isolation-by-distance. STRUCTURE revealed three subpopulations within the Bi-State consisting of the northern Pine Nut Mountains (PNa), mid Bi-State, and White Mountains (WM) following a north–south gradient. This genetic subdivision within the Bi-State is likely the result of habitat loss and fragmentation that has been exacerbated by recent human activities and the encroachment of singleleaf pinyon ( Pinus monophylla ) and juniper ( Juniperus spp.) trees. While genetic concerns may be only one of many priorities for the conservation and management of the Bi-State greater sage-grouse, we believe that they warrant attention along with other issues (e.g., quality of sagebrush habitat, preventing future loss of habitat). Management actions that promote genetic connectivity, especially with respect to WM and PNa, may be critical to the long-term viability of the Bi-State DPS.
Wildfires: Identification of a new suite of aromatic polycarboxylic acids in ash and surface water
Ash and surface water samples collected after wildfires in four different geographical locations (California, Colorado, Kansas and Alberta) were analyzed. The ash samples were leached with deionized water, and leachates were concentrated by solid phase extraction and analyzed by liquid chromatography/time-of-flight mass spectrometry. In addition, three surface water samples and a lysimeter water sample were collected from watersheds recently affected by fire in California and Colorado, and analyzed in similar fashion. A suite of benzene polycarboxylic acids (BPCAs), with two and three carboxyl groups and their corresponding isomers were identified for the first time in both ash leachates and water samples. Also found was a pyridine carboxylic acid (PCA), 3,5-pyridine dicarboxylic acid. Furthermore, putative identifications were made for other carboxylated aromatic acids: quinolinic, naphthalenic, and benzofuranoic acid carboxylates. The wildfire ashes, a controlled wood ash, and post-fire surface water samples suggest that burned woody material, along with surface plant-material and heated o-horizon soil organic matter, contribute to both BPCAs and PCAs in runoff. This study is the first of its kind to identify this suite of aromatic acids in wildfire ash and surface water samples. These data make an important contribution to the nature of dissolved organic matter from wildfire and are useful to better understand the impact of wildfire on water quality and drinking water sources.
Ground-water and related geology of Joshua Tree National Monument, California
Joshua Tree National Monument is in a mountainous part of the desert region of southern California. The geographic center of the monument is about 130 miles east of Los Angeles, Calif.; the area Investigated, covering almost 1,000 square miles in area, is included between 115?20' and 116?28' west longitude, and 33?04 ' and 34?07' north latitude.
Fire risk in San Diego County, California: A weighted Bayesian model approach
Fire risk models are widely utilized to mitigate wildfire hazards, but models are often based on expert opinions of less understood fire-ignition and spread processes. In this study, we used an empirically derived weights-of-evidence model to assess what factors produce fire ignitions east of San Diego, California. We created and validated a dynamic model of fire-ignition risk based on land characteristics and existing fire-ignition history data, and predicted ignition risk for a future urbanization scenario. We then combined our empirical ignition-risk model with a fuzzy fire behavior-risk model developed by wildfire experts to create a hybrid model of overall fire risk. We found that roads influence fire ignitions and that future growth will increase risk in new rural development areas. We conclude that empirically derived risk models and hybrid models offer an alternative method to assess current and future fire risk based on management actions.
Variation in leaf reflectance spectra across the California flora partitioned by evolutionary history, geographic origin, and deep time
Evolutionary relatedness underlies patterns of functional diversity in the natural world. Hyperspectral remote sensing has the potential to detect these patterns in plants through inherited patterns of leaf reflectance spectra. We collected leaf reflectance data from across the California flora from plants grown in a common garden. Regions of the reflectance spectra vary in the depth and strength of phylogenetic signal. We also show that these differences are much greater than variation due to the geographic origin of the plant. At the phylogenetic extent of the California flora, spectral variation explained by the combination of ecotypic variation (divergent evolution) and convergent evolution of disparate lineages was minimal (3 to 7 %) but statistically significant. Interestingly, at the extent of a single genus ( Arctostaphylos ) no unique variation could be attributed to geographic origin. However, up to 18% of the spectral variation among Arctostaphylos individuals was shared between phylogeny and intraspecific variation stemming from ecotypic differences (i.e., geographic origin). Future studies could conduct more structured experiments (e.g., transplants or observations along environmental gradients) to disentangle these sources of variation and include other intraspecific variation (e.g., plasticity). We constrain broad scale spectral variability due to ecotypic sources, providing further support for the idea that phylogenetic clusters of species might be detectable through remote sensing. Phylogenetic clusters could represent a valuable dimension of biodiversity monitoring and detection.
Diversity, composition, and geographical distribution of microbial communities in California salt marsh sediments
The Pacific Estuarine Ecosystem Indicators Research Consortium seeks to develop bioindicators of toxicant-induced stress and bioavailability for wetland biota. Within this framework, the effects of environmental and pollutant variables on microbial communities were studied at different spatial scales over a 2-year period. Six salt marshes along the California coastline were characterized using phospholipid fatty acid (PLFA) analysis and terminal restriction fragment length polymorphism (TRFLP) analysis. Additionally, 27 metals, six currently used pesticides, total polychlorinated biphenyls and polycyclic aromatic hydrocarbons, chlordanes, nonachlors, dichlorodiphenyldichloroethane, and dichlorodiphenyldichloroethylene were analyzed. Sampling was performed over large (between salt marshes), medium (stations within a marsh), and small (different channel depths) spatial scales. Regression and ordination analysis suggested that the spatial variation in microbial communities exceeded the variation attributable to pollutants. PLFA analysis and TRFLP canonical correspondence analysis (CCA) explained 74 and 43% of the variation, respectively, and both methods attributed 34% of the variation to tidal cycles, marsh, year, and latitude. After accounting for spatial variation using partial CCA, we found that metals had a greater effect on microbial community composition than organic pollutants had. Organic carbon and nitrogen contents were positively correlated with PLFA biomass, whereas total metal concentrations were positively correlated with biomass and diversity. Higher concentrations of heavy metals were negatively correlated with branched PLFAs and positively correlated with methyl- and cyclo-substituted PLFAs. The strong relationships observed between pollutant concentrations and some of the microbial indicators indicated the potential for using microbial community analyses in assessments of the ecosystem health of salt marshes. Copyright ?? 2006, American Society for Microbiology. All Rights Reserved.
Slope and aspect classifications of Lake Tahoe Basin, California and Nevada
A geographic information system was used to develop maps of slope and aspect data for the Lake Tahoe basin of California and Nevada. The maps were pro- duced at 1:100,000 scale by using digital-elevation data derived from 1:24,000-scale maps. The maps show slope (steepness) and aspect (compass-direction) data for the basin. Classes for slope data were set as follows: 0 percent, >0 to 2 percent, >2 to 5 percent, >5 to 10 percent, >10 to 15 percent, >15 to 20 percent, >20 to 30 percent, >30 to 50 percent, and >50 to 100 percent. Classes for aspect data were limited to the eight points of the compass (north, northeast, east, southeast, south, southwest, west, and northwest) and level land.
California and Landsat
California has remarkable geographic diversity, from 1,100 miles of Pacific shoreline to 33 million acres of trees, including its famous redwood forests along the Pacific Coast Highway, U.S. Route 101. And although California’s nickname is “The Golden State," it may also deserve the title of “The Extreme State.” Mount Whitney, the highest peak in the conterminous United States, stands at 14,494 feet above sea level in the Sierra Nevada mountain range. Just 2.5 hours away by car, Death Valley’s Badwater Basin boasts the lowest point in the United States: 282 feet below sea level. Although hundreds of inches of snow fall on Mount Whitney each year, the rainfall in Death Valley, commonly called the hottest place on Earth, averages less than 2 inches. California is the most populous U.S. State with 39 million residents, 26 million of whom live near the coast. It’s also the most agriculturally productive State, raising a variety of fruits, vegetables, nuts, grains, grasses, and flowers in addition to dairy and livestock. Although climate change affects many of these people, production, and places, Landsat can help agencies and residents monitor their landscapes and plan for a resilient future.
A natural resource condition assessment for Sequoia and Kings Canyon National Parks: Appendix 14: plants of conservation concern
Sequoia and Kings Canyon National Parks are located in the California Floristic Province, which has been named one of world‘s hotspots of endemic biodiversity (Myers et al. 2000). The California Floristic Province is the largest and most important geographic floristic unit in California and extends from the Klamath Mountains of southwestern Oregon to the northwestern portion of Baja California (Hickman 1993). The Sierra Nevada, one of six regions that make up the California Floristic Province, covers nearly 20% of the land in California yet contains over 50% of its flora. Within the Sierra Nevada, the southern Sierra supports more Sierran endemic and rare plant taxa than the central and northern portions of the region (Shevock 1996). Sequoia and Kings Canyon National Parks (SEKI) encompass roughly 20% of the southern Sierra Nevada region. The parks overlap three floristic subregions (central Sierra Nevada High, southern Sierra Nevada High, and southern Sierra Nevada Foothills), and border the Great Basin Floristic Province. The parks support a rich and diverse vascular flora composed of over 1,560 taxa. Of these, 150 taxa are identified as having special status. The term special status is applied here to include taxa that are state or federally listed, rare in California, or at risk because they have a limited distribution. Only one species from these parks is listed under the state or federal Endangered Species Acts ( Carex tompkinsii , Tompkins‘ sedge, is listed as a rare species under the California Endangered Species Act), and one species is under review for federal endangered listing ( Pinus albicaulis , whitebark pine). However, an absence of threatened and endangered species recognized by Endangered Species Acts is not equivalent to an absence of species at risk. There are 83 plant taxa documented as occurring in SEKI that are considered imperiled or vulnerable in the state by the California Department of Fish and Game‘s California Natural Diversity Database (CNDDB 2010a). There are an additional 66 taxa not formally listed by CNDDB that are recognized as having special status because their distribution is restricted to the Sierra Nevada. Special status plants are distributed throughout the two parks and inhabit a wide range of environments along the length of the elevation gradient that characterizes these parks. Ideally, we would assess the condition (status and trends) of each of the taxa on the SEKI special status plant list, documenting current population sizes, demographic rates and demographic trends. We would also hope to quantify the effects of individual stressors on each species based on existing monitoring and research. However, no data are available for most of the species on the special status plant list. For those few species (12 herbaceous species and two tree species) for which we possess some change over time information, the data are not adequate to make a competent assessment. Note that we have not explored the tree demographic information in any detail, as is covered in the NRCA Intact Forest/Five Needle Pines and Sequoia chapters. In general, we are unable to present an ‗integrity‘ metric for special status species in the parks, since the data to quantify the condition of each species in such a manner is not available. In contrast, the park does possess substantial data describing biodiversity in the parks. Therefore, our analysis focuses on describing the distribution and rarity of special status plants within the parks, with a particular focus on assessing the spatial distribution of species richness. We hope that such information will prove useful to park managers in determining which areas in the parks merit the most attention (for example in developing monitoring protocols). We also assess potential vulnerability of special status species to the stressors chosen by the NRCA working group, using both park data and available literature. As a first step, we spent considerable effort updating and refining the criteria for the special status plant list, as this list defines which taxa are considered in our assessment. Observation data of these species was then compiled from all known sources in order to provide a comprehensive view of where special status plants have been documented and, ultimately, to enable the most informed determinations of areas in the parks that potentially support the highest number of rare and endemic taxa. These ‗hot spot‘ analyses are presented by geographic region, vegetation type and elevation. For these and other analyses presented in this report, we place more focus on summarizing findings for the herbaceous and shrub special status taxa than on special status trees. The trees which qualify as special status are the focus of other NRCA chapters, including Giant Sequoia and Intact Forests/Five-needle Pines. We do, however, present their mapped distributions and provide overviews of research related to the special status tree taxa in the Stressors section of this report.
Cenozoic giant pectinids from California and the Tertiary Caribbean Province: Lyropecten, "Macrochlamis," Vertipecten, and Nodipecten species
Tertiary pectinids recognized for more than 125 years by field geologists can now be used to date and correlate 3-4 m.y. increments of the geologic record and to determine faunal distributions in relation to tectonic terranes. Fossil pectinids are commonly preserved in shallowmarine clastic deposits that mostly lack microfossils. The stratigraphic ranges of Lyropecten, "Macrochlamis," Vertipecten , and Nodipecten can be used to subdivide provincial megafaunal stages in California and to correlate chronostratigraphic units in the Pacific Northwest and Atlantic Coastal Plain. One New World taxon, "Macrochlamis" magnolia ojaiensis, n. subsp., supports a direct correlation between the middle "Vaqueros" Stage of California (interpolated as 27-23 m.y. B.P.) and an Upper Chattian-Lower Aquitanian Stage section in southwestern Switzerland. Two lithologic units widespread in California, the Vaqueros Formation (spanning 12 m.y., from the late Oligocene into the early Miocene) and Temblor Formation (deposited over a period of 26 m.y., from the late Eocene or early Oligocene to the middle Miocene), transgress much longer periods of time than have been generally recognized. Certain species pairs are identified as cognates, close relatives descended from a common ancestor. Close similarities are found between widely separated assemblages from the Salton Trough of California and the Caribbean, the Gulf Coastal Plain of eastern Mexico and the Sinu Valley of western Colombia, the Santa Rosalia area in Baja California Sur, Mexico, and the Paraguana Peninsula of Venezuela. Distribution patterns for relatively recently dispersed taxa have important implications for middle to late Cenozoic paleogeography and tectonic history, especially in west Mexico and the Caribbean. Speciation was concurrent with the closure of the Isthmus of Panama, the opening of the Gulf of California, and possibly with the northward translation of segments of the California Continental Borderland. Tertiary Caribbean and PacificPanamic Lyropectens and Nodipectens are plotted on a simplified tectonic map as an early step in considering Cenozoic molluscan distributions in relation to major plate boundaries. Taxa having unusual distributions are tabulated with the tectonic events that may have modified their observed geographic ranges. Southern California and the Baja California peninsula include tectonostratigraphic terranes and tectonic slivers that may have moved on the order of hundreds or thousands of kilometers in the Paleogene. Relations between recently dispersed faunas and tectonic terrane boundaries are further complicated by short-term variations in oceanographic phenomena such as currents, El Nino events, and shifts in areas of upwelling. Lyropecten evolved in the late Oligocene or early Miocene, Nodipecten by the late middle Miocene. According to the classification used here, Lyropecten still lives in the Galapagos. Holocene Nodipectens divide the Pacific-Panamic and Caribbean provinces into two subprovinces each. Habitat, life history, dispersal, and growth data are summarized for living Nodipectens, whose distinctive shell features include ledges and hollow nodes. Phylogenetic lineages are based on progressive trends in node formation and rib schemes, some of which have biostratigraphic significance.
Documentation and description of the digital spatial data base for southern California Regional Aquifer-System Analysis Program, Santa Clara-Calleguas Basin, Ventura County, California
This report documents the geographic information system map layers and data files generated for the Santa Clara-Calleguas Basin, Ventura County, as part of a Regional Aquifer- System Analysis of southern California from 1989 to 1995. Thirty-six map layers and four data files are maintained in this geographic information system data base. The map layers cover the Santa Clara-Calleguas drainage basin and are stored in a common map projection. Attributes of the map layers and data files are described and referenced. The map layers are grouped by geography, geology, and hydrology.