Carrizo Plain Research Articles

Characterizing the soil microbial community associated with the fungal pathogen Coccidioides immitis.

Coccidioidomycosis is a fungal disease affecting humans and other mammals, caused by environmental pathogens of the genus Coccidioides . Understanding the ecological factors that shape the distribution of Coccidioides in soils is important for minimizing the risk of human exposure, though this remains challenging due to the pathogen's highly variable spatial distribution. Here, we examined associations between the soil microbial community and Coccidioides immitis presence within the Carrizo Plain National Monument-a minimally disturbed grassland ecosystem, and the site of a longitudinal study examining the effects of rodents and their burrows on C. immitis presence in soils. Using internal transcribed spacer 2 (ITS2) and 16S sequencing to characterize the soil fungal and bacterial communities, we found over 30 fungal species, including several other members of the Onygenales order, that co-occurred with Coccidioides more frequently than expected by chance. Coccidioides -positive samples were significantly higher in microbial diversity than negative samples, an association partly driven by higher Coccidioides presence within rodent burrows compared to surface soils. Soil source ( i.e., rodent burrow versus surface soil) explained the largest amount of variation in bacterial and fungal community diversity and composition, with soils collected from rodent burrows having higher microbial diversity than those collected from adjacent surface soils. While prior evidence is mixed regarding associations between Coccidioides and microbial diversity, our study suggests that favorable microhabitats such as rodent burrows can lead to a positive association between soil diversity and Coccidioides presence, particularly in otherwise resource-limited natural environments.

A Preliminary Exploration of an Understudied Lichen Flora: Lichens of the Basin of Carrizo Plain National Monument, California

A Preliminary Exploration of an Understudied Lichen Flora: Lichens of the Basin of Carrizo Plain National Monument, California

Geochemical Record of Late Quaternary Paleodepositional Environment from Lacustrine Sediments of Soda Lake, Carrizo Plain, California

This study investigates the responses of the depositional environments of Soda Lake sediments to climatic shifts from the Last Glacial Maximum to the Holocene epoch based on the results of major and trace elements of the North Soda Lake (NSL) NSL1A core. The NSL1A core records the sedimentary evolution of the Soda Lake watershed since at least 25 cal ka BP. Element analyses provide evidence that Soda Lake sediments are mostly derived from marine sequences in the Southern Coast Ranges of California. Variation in proxies for paleoweathering, paleoclimate, paleosalinity, paleoproductivity, paleoredox, and water depth is utilized to reconstruct the evolution of the sedimentary environment. The Chemical Index of Alteration (CIA) values indicate low to moderate chemical weathering in the sediment source regions. Paleoredox proxies indicate that the NSL1A core formed in a mainly subreduction environment. The NSL1A core is divided into four zones based on the results of the proxies. Zone 4 (5.0–5.8 m) of the sediment core indicates stable hydroclimatic conditions with low and constant sand and silt content, suggesting a warm and relatively humid environment. Zone 3 (3.35–5.0 m) represents the early half of the Last Glacial Maximum interval and a high lake stand. The elevated sand content suggests postflood events due to the northerly migration of westerly storm tracks. Zone 2 (1.075–3.35 m) reveals nuanced changes, including decreasing salinity, slight increases in wetness, detrital trace metals, and paleoproductivity. These subtle shifts suggest a multifaceted environmental evolution: a trend toward wetter conditions alongside a prolonged shift from cooler to warmer periods. Zone 1 (0.15–1.075 m) spans the Lateglacial to Holocene transition as well as Early and Middle Holocene, marked by significant hydrologic and ecologic variability including rapid warming during the Bølling–Allerød and rapid cooling linked to the Younger Dryas.

Shrub density effects on the presence of an endangered lizard of the Carrizo Plain National Monument, California.

Positive associations between animals and foundational shrub species are frequent in desert ecosystems for shelter, resources, refuge, and other key ecological processes. Herein, we tested the impact of the density of the shrub species Ephedra californica on the presence and habitat use of the federally endangered lizard species, Gambelia sila. To do this, we used a 3-year radio telemetry dataset and satellite-based counts of shrub density across sites at the Carrizo Plain National Monument in San Luis Obispo County, CA. The effect of shrub density on lizard presence was contrasted with previous shrub cover analyses to determine whether measures of shrub density were superior to shrub cover in predicting lizard presence. Increasing shrub density increased lizard presence. As shrub density increased, lizards were located more frequently "above ground" versus "below ground" in burrows. Male lizards had significantly larger home ranges than females, but both sexes were similarly associated with increasing shrub densities. Shrub density and shrub cover models did not significantly differ in their prediction of lizard presence. These findings suggest that both habitat measures are effective analogs and that ecologically, both cover and the density of foundation shrub species are key factors for some desert lizards.

Channel Incision Ages to the Rescue: An Improved Age for the Penultimate Earthquake That Ruptured the Carrizo Section of the South-Central San Andreas Fault

ABSTRACT A primary step toward assessing the time and size of future earthquakes is identifying earthquake recurrence patterns in the seismic record. The San Andreas fault (SAF) is one of the most studied active faults in the world. However, there is no unequivocal interpretation of paleoseismic data to determine the timing and rupture extent of the earthquakes that occurred prior to the historical 1857 and 1906 ruptures. The penultimate earthquake is the least well-dated earthquake along the Cholame, Carrizo, and Big Bend sections of the SAF. The main reason for this poor determination is because the past few hundred years have seen large natural fluctuations in atmospheric C14 concentration. These fluctuations mean that a single radiocarbon date may yield a calibrated age consisting of several possible age ranges. At sites along frequently rupturing faults with historical ruptures, such as the SAF and the North Anatolian fault in Turkey, determining the incision age of channels displaced only by the most recent earthquake can place a tighter minimum limit on the possible age range of the penultimate earthquake. In our study, we dated five sandy fill units with the post-infrared infrared-stimulated luminescence method on single feldspar grains of channel Sieh 31 in the Carrizo Plain. The data indicate the channel Sieh 31, offset ∼6 m during the 1857 earthquake, incised before ∼1740 ± 30 C.E. (1σ). This new result trims the age constraint of the penultimate earthquake that ruptured the Carrizo section of the SAF determined at the nearby Bidart Fan site from 1640–1857 to 1631–1745 C.E., tightening the age constraint by nearly 80 yr. The revised mean recurrence interval for surface rupturing earthquakes along the Carrizo section of the south-central SAF is 117 yr (95% confidence interval 62–255 yr). This approach can improve paleoearthquake age and slip-per-earthquake constraints.

Two new alkali-sink specialist species of Paruroctonus Werner 1934 (Scorpiones, Vaejovidae) from central California.

Herein we describe two new species of Paruroctonus (Werner 1934) from California: Paruroctonussoda sp. nov. from the Soda Lake playa at the center of the Carrizo Plain in San Luis Obispo county and Paruroctonusconclusus sp. nov. from the Koehn Lake playa in the Mojave Desert of Kern County. They can be differentiated from other Paruroctonus by a combination of morphological features including deeply scalloped pedipalp fingers in males, specific patterns of fuscous pigmentation, unique setal counts, and unique morphometric ratios. They can also be separated from one another by the latter three characters. Photographs of a large selection of live scorpions are provided, including detailed images and figures of many morphological features. Their distributions, habitats, and ecologies are discussed; and important steps towards their conservation are described.

The life span of fault-crossing channels.

Successive earthquakes can drive landscape evolution. However, the mechanism and pace with which landscapes respond remain poorly understood. Offset channels in the Carrizo Plain, California, capture the fluvial response to lateral slip on the San Andreas Fault on millennial time scales. We developed and tested a model that quantifies competition between fault slip, which elongates channels, and aggradation, which causes channel infilling and, ultimately, abandonment. Validation of this model supports a transport-limited fluvial response and implies that measurements derived from present-day channel geometry are sufficient to quantify the rate of bedload transport relative to slip rate. Extension of the model identifies the threshold for which persistent change in transport capacity, obliquity in slip, or advected topography results in reorganization of the drainage network.

Golden Eagle Breeding Response to Utility-Scale Solar Development and Prolonged Drought in California

Each year from 2012–2016, we conducted helicopter surveys to monitor the distribution, success, and productivity of Golden Eagles (Aquila chrysaetos) breeding within 16 km of California Valley Solar Ranch (CVSR) in San Luis Obispo County, California. This 250-megawatt photovoltaic solar plant was built over 2 yr on 642 ha of disturbed grassland and desert scrub habitat on Carrizo Plain, and was operational in October 2013. Beginning in 2012 coincident with initial CVSR development, the study area and region experienced a severe drought that persisted through the end of the 2016 breeding season. During the study, we detected and monitored 19 variably occupied Golden Eagle breeding territories. We confirmed a similar number of occupied territories in 2012 (15) and 2016 (16), but our ability to reliably confirm pairs declined during the drought and shifting territory dynamics occurred in several areas. Between 2012 and 2015, the proportion of pairs that laid eggs (breeding rate) and fledgling production per occupied territory (productivity) declined by 93–95% (13 pairs laid eggs in 2012; only 1 pair did so in 2015). In 2016, the breeding rate increased sharply again to 63% of occupied territories (87% in 2012) following the return of average rainfall during the preceding winter, but the proportion of pairs that fledged young and productivity rebounded to notably lesser degrees. The eagle breeding rate and productivity trends were strongly correlated with current-year measures of primary plant productivity and rainfall totals from the previous water-year (June–July). Breeding performance metrics for five pairs with territories situated on the periphery of Carrizo Plain and 13 pairs located elsewhere in the study area away from possible development disturbance did not differ statistically. This suggested that CVSR development and initial operation did not adversely affect eagle breeding performance during the study; however, we cannot draw definitive conclusions from this 5-yr study about how CVSR development might have influenced the local eagle breeding population. Instead, we concluded that a severe 5-yr drought dramatically reduced eagle breeding activity in the study area (and region) and confounded our effort to evaluate the effects of the solar development.

Shrub and vegetation cover predict resource selection use by an endangered species of desert lizard

Globally, no species is exempt from the constraints associated with limited available habitat or resources, and endangered species in particular warrant critical examination. In most cases, these species are restricted to limited locations, and the relative likelihood of resource use within the space they can access is important. Using Gambelia sila, one of the first vertebrate species listed as endangered, we used resource selection function analysis of telemetry and remotely sensed data to identity key drivers of selected versus available locations for this species in Carrizo Plain National Monument, USA. We examined the probability of selection given different resource types. Increasing shrub cover, lower and relatively more flat sites, increasing normalized difference vegetation index, and solar radiation all significantly predicted likelihood of observed selection within the area sampled. Imagery data were also validated with fine-scale field data showing that large-scale contrasts of selection relative to available location patterns for animal species are a useful lens for potential habitat. Key environmental infrastructure such as foundation plant species including shrubs or local differences in the physical attributes were relevant to this endangered species.

A physics-based approach of deep interseismic creep for viscoelastic strike-slip earthquake cycle models

SUMMARYMost geodetic inversions of surface deformation rates consider the depth distribution of interseismic fault slip-rate to be time invariant. However, some numerical simulations show downdip penetration of dynamic rupture into regions with velocity-strengthening friction, with subsequent updip propagation of the locked-to-creeping transition. Recently, Bruhat and Segall developed a new method to characterize interseismic slip rates, that allows slip to penetrate up dip into the locked region. This simple model considered deep interseismic slip as a crack loaded at its downdip end, and provided analytical expressions for stress drop within the crack, slip and slip rate along the fault. This study extends this approach to strike-slip fault environments, and includes coupling of creep to viscoelastic flow in the lower crust and upper mantle. I use this model to investigate interseismic deformation rates along the Carrizo Plain section of the San Andreas fault. This study reviews possible models, elastic and viscoelastic, for fitting horizontal surface rates. Using this updated approach, I develop a physics-based solution for deep interseismic creep which accounts for possible slow vertical propagation, and investigate how it improves the fit of the horizontal deformation rates in the Carrizo Plain region. I found solutions for fitting the surface deformation rates that allow for reasonable estimates for earthquake rupture depth and coseismic displacement and improves the overall fit to the data. Best-fitting solutions present half-space relaxation time around 70 yr, and very low propagation speeds, less than a metre per year, suggesting a lack of creep propagation.

The dark side of facilitation: native shrubs facilitate exotic annuals more strongly than native annuals

Positive interactions enhance biodiversity and ecosystem function, but can also exacerbate biological invasions. Facilitation of exotic invaders by exotic foundation species (invasional meltdown) has been studied extensively, but facilitation of exotic invaders by native foundation species has attracted less attention. Specifically, very few studies have examined the extent that native foundation species facilitate native and exotic competitors. Understanding the processes that mediate interactions between native and exotic species can help explain, predict, and improve management of biological invasions. Here, we examined the effects of native foundation shrubs on the relative abundance of the annual plant community – including native and exotic taxa – from 2015–2018 in a desert ecosystem at Carrizo Plain National Monument, California, USA (elevation: 723 m). Shrub effects varied by year and by the identity of annual species, but shrubs consistently enhanced the abundance of the annual plant community and facilitated both native (n=17 species) and exotic (n=4 species) taxa. However, at the provenance level, exotic annuals were facilitated 2.75 times stronger in abundance than native annuals, and exotic annuals were always more abundant than natives both near and away from shrubs. Our study reaffirms facilitation as an important process in the organisation of plant communities and confirms that both native and exotic species can form positive associations with native foundation species. However, facilitation by native foundation species can exacerbate biological invasions by increasing the local abundance of exotic invaders. Thus, the force of facilitation can have a dark side relevant to ecosystem function and management.

Reproducibility of San Andreas Fault Slip Rate Measurements at Wallace Creek in the Carrizo Plain, CA

AbstractReproducibility of results from scientific studies is rarely demonstrated outside the laboratory. Measurements of fault slip rate underpin scientific models of active faulting and seismic hazard assessments widely used for policymaking and risk mitigation. We replicated a highly referenced study that measured the slip rate as 33.9 ± 2.9 mm/year along the San Andreas fault over the past ~3,700 years at Wallace Creek in the Carrizo Plain National Monument, USA. Our results provide a slip rate of slip 36 ± 1 mm/year since ~3,500 CalBP. We find that the late Holocene slip rate of the San Andreas fault, a key indicator of seismic hazard, is reproducible within measurement uncertainty. Geologic slip rate determinations are relatively insensitive to short‐term fluctuations and thus should be reproducible if the time interval of measurement is much greater than the average rupture interval.

Kleptoparasitism of Harvester Ants by the Giant Kangaroo Rat (Dipodomys ingens) in the Carrizo Plain, California

Abstract. Kangaroo rats are reported to have a mutualistic relationship with harvester ants through facilitation of burrow establishment, creation, and persistence. The relationship can, however, become more complex. We report observations of the giant kangaroo rat (Dipodomys ingens), a state and federally listed endangered species, repeatedly kleptoparasitizing harvester ants from a nearby nest in the Carrizo Plain, California. Though the relationship between kangaroo rats and harvester ants has been studied extensively and is believed to be mutualistic, under certain conditions this relationship can follow an alternate path of parasitism.

The Age and Origin of Small Offsets at Van Matre Ranch along the San Andreas Fault in the Carrizo Plain, California

The Age and Origin of Small Offsets at Van Matre Ranch along the San Andreas Fault in the Carrizo Plain, California

Seismic and Aseismic Moment Budget and Implication for the Seismic Potential of the Parkfield Segment of the San Andreas Fault

This study explores methods to assess the seismic potential of a fault based on geodetic measurements, geological information of fault‐slip rate, and seismicity data. The methods are applied to the Parkfield section along the San Andreas fault (SAF) at the transition zone between the SAF creeping segment in the north and the locked section of Cholame to the south, where M_w ∼6 earthquakes occurred every 24.5 yrs on average since the 1857 M_w 7.7 Fort Tejon earthquake. We compare the moment released by the known earthquakes and associated postseismic deformation with the moment deficit accumulated during the interseismic period derived from geodetic measurement of interseismic strain. We find that the recurring M_w 6 earthquakes are insufficient to balance the slip budget. We discuss and evaluate various possible scenarios which might account for the residual moment deficit and implications of the possible magnitude and return period of M_w >6 earthquakes on that fault segment. The most likely explanation is that this fault segment hosts M_w 6.5–7.5 earthquakes, with a return period of 140–300 yrs. Such events could happen as independent earthquakes in conjunction with ruptures of the Carrizo plain segment of the SAF. We show how the results from our analysis can be formally incorporated in probabilistic seismic hazard assessment assuming various magnitude–frequency distribution and renewal time models.

A picture is worth a thousand data points: an imagery dataset of paired shrub-open microsites within the Carrizo Plain National Monument

BackgroundCarrizo Plain National Monument (San Joaquin Desert, California, USA) is home to many threatened and endangered species including the blunt-nosed leopard lizard (Gambelia sila). Vegetation is dominated by annual grasses, and shrubs such as Mormon tea (Ephedra californica), which is of relevance to our target species, the federally listed blunt-nosed leopard lizard, and likely also provides key ecosystem services. We used relatively nonintrusive camera traps, or trail cameras, to capture interactions between animals and these shrubs using a paired shrub-open deployment. Cameras were placed within the shrub understory and in open microhabitats at ground level to estimate animal activity and determine species presence.FindingsTwenty cameras were deployed from April 1st, 2015 to July 5th, 2015 at paired shrub-open microsites at three locations. Over 425,000 pictures were taken during this time, of which 0.4 % detected mammals, birds, insects, and reptiles including the blunt-nosed leopard lizard. Trigger rate was very high on the medium sensitivity camera setting in this desert ecosystem, and rates did not differ between microsites.ConclusionsCamera traps are an effective, less invasive survey method for collecting data on the presence or absence of desert animals in shrub and open microhabitats. A more extensive array of cameras within an arid region would thus be an effective tool to estimate the presence of desert animals and potentially detect habitat use patterns.

A Fault‐Based Model for Crustal Deformation, Fault Slip Rates, and Off‐Fault Strain Rate in California

We invert Global Positioning System (GPS) velocity data to estimate fault slip rates in California using a fault‐based crustal deformation model with geologic constraints. The model assumes buried elastic dislocations across the region using Uniform California Earthquake Rupture Forecast Version 3 (UCERF3) fault geometries. New GPS velocity and geologic slip‐rate data were compiled by the UCERF3 deformation working group. The result of least‐squares inversion shows that the San Andreas fault slips at 19–22 mm/yr along Santa Cruz to the North Coast, 25–28 mm/yr along the central California creeping segment to the Carrizo Plain, 20–22 mm/yr along the Mojave, and 20–24 mm/yr along the Coachella to the Imperial Valley. Modeled slip rates are 7–16 mm/yr lower than the preferred geologic rates from the central California creeping section to the San Bernardino North section. For the Bartlett Springs section, fault slip rates of 7–9 mm/yr fall within the geologic bounds but are twice the preferred geologic rates. For the central and eastern Garlock, inverted slip rates of 7.5 and 4.9 mm/yr, respectively, match closely with the geologic rates. For the western Garlock, however, our result suggests a low slip rate of 1.7 mm/yr. Along the eastern California shear zone and southern Walker Lane, our model shows a cumulative slip rate of 6.2–6.9 mm/yr across its east–west transects, which is ∼1 mm/yr increase of the geologic estimates. For the off‐coast faults of central California, from Hosgri to San Gregorio, fault slips are modeled at 1–5 mm/yr, similar to the lower geologic bounds. For the off‐fault deformation, the total moment rate amounts to 0.88×1019 N·m/yr, with fast straining regions found around the Mendocino triple junction, Transverse Ranges and Garlock fault zones, Landers and Brawley seismic zones, and farther south. The overall California moment rate is 2.76×1019 N·m/yr, which is a 16% increase compared with the UCERF2 model. Online Material: Table of geological slip rates.

Non-invasive baseline genetic monitoring of the endangered San Joaquin kit fox on a photovoltaic solar facility

Survival of endangered San Joaquin kit foxes Vulpes macrotis mutica is challenged by reduced and fragmented habitat resulting from anthropogenic uses. We monitored kit foxes on the 40 km2 proposed site for the Topaz Solar Farms (TSF) in San Luis Obispo County, California, which consisted of 76% agricultural fields and 24% grasslands. Prior to construction of the solar facility in December 2011, we used professionally trained dog-handler teams to conduct noninvasive genetic surveys annually from 2009 to 2011. We analyzed mtDNA to identify species, zinc finger genes for sex determination, and microsatellite loci to define individuals. We identified 45 individuals from 351 fresh scat samples (26 females, 18 males, and 1 individual of unknown sex), and recaptured 5 individuals between years. Kit foxes predominantly used the grasslands and rarely used agricultural fields. Samples from the TSF population had similar levels of genetic diversity to 2 areas less than 20 km away in the northern end of the Carrizo Plain National Monument. Capwire and LDNe estimates of population size using samples collected during annual November surveys indicated that ~33 individuals used the TSF over a 3 yr period. The relatively high population estimate, low recapture rates, and similar genetic diversity to 2 nearby locations suggest that individuals using the TSF site are part of a larger population using the surrounding landscape. Our study provided baseline data that, when coupled with future surveys, will help assess the effects on San Joaquin kit foxes of solar facility construction and habitat regeneration on agricultural lands removed from production.

Big solar's big surge

Silence generally reigns across California's Carrizo Plain, about 160 kilometers northwest of Los Angeles. But for much of the past three years, this expanse of grassland and farms was anything but silent, as up to 880 people trucked out each day to the plain's sparsely inhabited northern end to build a hefty power plant. On a bright October afternoon, only a handful of construction workers remain, and the nearly completed plant is generating at close to full tilt. And yet it makes naryas it pumps hundreds of megawatts of electricity into California's power grid. a click, buzz, or whir, even

Three-Dimensional Investigation of a 5 m Deflected Swale along the San Andreas Fault in the Carrizo Plain

Topographic maps produced from Light Detection and Ranging (LiDAR) data are useful for paleoseismic and neotectonic research because they pro- vide submeter representation of faulting-related surface features. Offset measurements of geomorphic features, made in the field or on a remotely sensed imagery, commonly assume a straight or smooth (i.e., undeflected) pre-earthquake geometry. Here, we present results from investigation of an ∼20 cm deep and >5 m wide swale with a sharp bend along the San Andreas fault (SAF) at the Bidart fan site in the Carrizo Plain, California. From analysis of LiDAR topography images and field measure- ments, the swale was initially interpreted as a channel tectonically offset ∼4:7 m. Our observations from exposures in four backhoe excavations and 25 hand-dug trenchettes show that even though a sharp bend in the swale coincides with the trace of the A.D. 1857 fault rupture, the swale formed after the 1857 earthquake and was not tectonically offset. Subtle fractures observed within a surficial gravel unit overlying the 1857 rupture trace are similar to fractures previously documented at the Phelan fan and LY4 paleoseismic sites 3 and 35 km northwest of Bidart fan, respectively. Collectively, the fractures suggest that a post-1857 moderate-magnitude earthquake caused ground cracking in the Carrizo and Cholame stretches of the SAF. Our obser- vations emphasize the importance of excavation at key locations to validate remote and ground-based measurements, and we advocate more geomorphic characterization for each site if excavation is not possible. Online Material: Figures of trench logs.