Central California Research Articles

Evidence of Temperature‐Driven Shifts in Market SquidDoryteuthis opalescensDensities and Distribution in the California Current Ecosystem

AbstractClimate change is impacting the abundance and distribution of marine resources. The consequences of these impacts are likely to alter trophic interactions between species within an ecosystem and affect fisheries opportunities for coastal communities. Market squidDoryteuthis opalescenscomprise the largest fishery (by volume) in California, USA, and questions persist about whether the changing ocean conditions are leading to an increase in squid abundance in traditional fishing locations as well as marginal habitats in northern areas. To examine this potential phenomenon, we used fisheries‐independent survey data collected by the National Marine Fisheries Service between 1998 and 2019 to develop a spatiotemporal model that estimates changes in the squid density from central California to northern Washington. We found a fivefold increase in the squid index of abundance across the entire spatial domain of the surveys during the sampling period, with the largest increases occurring in the Oregon and Washington strata. Although our model demonstrated that encounter rates and squid densities for the surveys increased in warmer and more saline waters, large shifts in squid distribution were only associated with deviations in ocean temperatures that could be characterized as marine heatwaves. This analysis adds to a growing body of work documenting the spatiotemporal response of marine resources to both long‐term trends in warming ocean conditions and episodic events, such as marine heatwaves. Furthermore, it demonstrates the need for ecosystem assessment models with the ability to forecast changes in species distribution and abundance at spatiotemporal scales that are relevant for coastal fishing communities.

Fetal mercury concentrations in central California Pacific harbor seals: Associated drivers and outcomes

Mercury (Hg) is a well-known toxicant in wildlife and humans. High total Hg concentrations ([THg]) have been reported in central California harbor seals Phoca vitulina richardii. We evaluated the effects of presence/absence of early natal coat (lanugo), year (2012 to 2017), sex, stranding location, and trophic ecology (ẟ13C and ẟ15N values) on hair [THg] along coastal central California. Also examined were [THg] effects on growth rates of pups in rehabilitation and probability of release (e.g., successful rehabilitation). The [THg] ranged from 0.46–81.98 mg kg−1 dw, and ẟ15N and ẟ13C ranged from 13.6–21.5‰, and −17.2 to −13.0‰, respectively. Stranding location, year, and presence of lanugo coat were important factors explaining variation in [THg]. Seals from Sonoma and San Mateo County had higher [THg] than other locations. Seals with full or partial lanugo coat had lower [THg]. Seals from 2016 and 2017 had higher [THg] than those from 2015. Hair [THg] exceeded lower and upper toxicological thresholds (>20 mg kg−1 by year (5.88% to 23.53%); >30 mg kg−1 (0% to 12.31%)) with a pronounced increase from 2015 to 2016. Pups in 2017 had significantly higher odds ratio of [THg] above 20 mg kg−1 than pups of 2015, and pups in 2016 had significantly higher odds ratio than those from 2013 and 2015 (similar when using 30 mg kg−1). Pups in Sonoma County had the highest odds ratio for [THg] in lanugo above 20 mg kg−1. ẟ15N values were higher in 2015–2017, particularly relative to 2014, probably associated with the El Niño event. The [THg] was not a good predictor for probability of release and mass-specific growth rates in captivity. Further investigation of temporal trends of [THg] in harbor seals is warranted given the relatively high percentage of samples exceeding threshold values, particularly in the most recent sampling years.

Chukchansi Yokuts

Chukchansi belongs to the Yokuts language family (ISO 639 code: yok) ancestrally spoken in the San Joaquin valley of Central California and in the adjacent foothills of the Sierra Nevada. The headquarters of the Chukchansi tribe is located in Coarsegold and many members of the tribe live in and around Madera and Fresno counties. As shown in the map in Figure 1, there are three major territories of the Yokuts: Northern Valley Yokuts, Foothill Yokuts, and Southern Valley Yokuts. While the territory of the Chukchansi is in the foothills area, the dialect is linguistically Northern Valley (Whistler & Golla 1986), as shown in Figure 2. Yawelmani, a Yokuts language that has been a subject of extensive linguistic research (e.g. Newman 1944, Archangeli 1983, Weigel 2005), is a dialect of the Southern Valley Yokuts. It is unclear to what extent Yokuts varieties are mutually intelligible. Yokuts is often considered to be a part of a larger Penutian language family (e.g. Dixon & Kroeber 1913, Sapir 1921, DeLancey & Golla 1997). While the status of Penutian as a macro-family is disputed, Yokuts is very likely related to the Miwok and Costanoan language families of California (Callaghan 1997).

Enhanced winter, spring, and summer hydroclimate variability across California from 1940 to 2019

AbstractCalifornia’s recent hydroclimatic pivots have caused billions of dollars in damages with the potential to become more extreme in the future, even if the mean total precipitation and streamflow do not change. In this study, we compile instrumental precipitation and streamflow records across California to quantify trends in hydroclimatic variability across spatial, temporal, and seasonal domains. We use the 10th and 90th percentiles of the distribution to examine whether any trends in variability are driven primarily by extreme low or high rainfall or streamflow events. Our analysis shows that there is a statistically significant positive trend in precipitation variability that is driven by long‐term increases to the 90th percentile through most of California during winter (January–March), which has been steadily increasing since the mid‐20th century. In contrast, significant positive streamflow trends are seen in winter, spring (April–June), and summer (July–September) and are driven by changes to both the 10th and 90th percentiles. Moreover, we found that there is a decreasing trend in fall (October–December) hydroclimatic variability, particularly over central California, that is related to declining values in the 90th percentile in both precipitation and streamflow. Our results suggest that California’s hydroclimate has been under a continually heightened state of volatility, leaving the state vulnerable to hydroclimatic extremes and elevated risk of associated compound events (floods, landslides, fires). Thus, water resources managers will need to incorporate this increased volatility into their planning for public and agricultural water supply, while being aware of the higher risks for wildfires and floods as well as the disproportionate and lasting impact on vulnerable ecosystem structures.

Burrowing crabs and physical factors hasten marsh recovery at panne edges.

Salt marsh loss is projected to increase as sea-level rise accelerates with global climate change. Salt marsh loss occurs along both lateral creek and channel edges and in the marsh interior, when pannes expand and coalesce. Often, edge loss is attributed to erosive processes whereas dieback in the marsh interior is linked to excessive inundation or deposition of wrack, but remains poorly understood. We conducted a two-year field investigation in a central California estuary to identify key factors associated with panne contraction or expansion. Our study explored how an abundant burrowing crab, shown to have strong negative effects on marsh biomass near creek edges, affects panne dynamics. We also explored which physical panne attributes best predicted their dynamics. To our knowledge, ours is the first study of panne dynamics in a California marsh, despite how ubiquitous pannes are as a feature of marshes in the region and how often extensive marsh dieback occurs via panne expansion. Overall, we found that pannes contracted during the study period, but with variable rates of marsh recovery across pannes. Our model incorporating both physical and biological factors explained 86% of the variation in panne contraction. The model revealed a positive effect of crab activity, sediment accretion, and a composite of depth and elevation on panne contraction, and a negative effect of panne size and distance to nearest panne. The positive crab effects detected in pannes contrast with negative effects we detected near creek edges in a previous study, highlighting the context-dependence of top-down and bioturbation effects in marshes. As global change continues and the magnitude and frequency of disturbances increases, understanding the dynamics of marsh loss in the marsh interior as well as creek banks will be critical for the management of these coastal habitats.

Effects of Smoking on SARS-CoV-2 Positivity: A Study of a Large Health System in Northern and Central California.

IntroductionCOVID-19 continues to impact vulnerable populations disproportionally. Identifying modifiable risk factors could lead to targeted interventions to reduce infections. The purpose of this study is to identify risk factors for testing positive for SARS-CoV-2.MethodsUsing electronic health records collected from a large ambulatory care system in northern and central California, the study identified patients who had a test for SARS-CoV-2 between 2/20/2020 and 3/31/2021. The adjusted effect of active and passive smoking and other risk factors on the probability of testing positive for SARS-CoV-2 were estimated using multivariable logistic regression. Analyses were conducted in 2021.ResultsOf 556 690 eligible patients in our sample, 70 564 (12.7%) patients tested positive for SARS-CoV-2. Younger age, being male, racial/ethnic minorities, and having mild major comorbidities were significantly associated with a positive SARS-CoV-2 test. Current smokers (adjusted OR: 0.69, 95% CI: 0.66-0.73) and former smokers (adjusted OR: 0.92, 95% CI: 0.89-0.95) were less likely than nonsmokers to be lab-confirmed positive, but no statistically significant differences were found when comparing passive smokers with non-smokers. The patients with missing smoking status (25.7%) were more likely to be members of vulnerable populations with major comorbidities (adjusted OR ranges from severe: 2.52, 95% CI = 2.36-2.69 to mild: 3.28, 95% CI = 3.09-3.48), lower income (adjusted OR: 0.85, 95% CI: 0.85-0.86), aged 80 years or older (adjusted OR: 1.11, 95% CI: 1.07-1.16), have less access to primary care (adjusted OR: 0.07, 95% CI: 0.07-0.07), and identify as racial ethnic minorities (adjusted OR ranges from Hispanic: 1.61, 95% CI = 1.56-1.65 to Non-Hispanic Black: 2.60, 95% CI = 2.5-2.69).ConclusionsOur findings suggest that the odds of testing positive for SARS-CoV-2 were significantly lower in smokers compared to nonsmokers. Other risk factors include missing data on smoking status, being under 18, being male, being a racial/ethnic minority, and having mild major comorbidities. Since those with missing data on smoking status were more likely to be members of vulnerable populations with higher smoking rates, the risk of testing positive for SARS-CoV-2 among smokers may have been underestimated due to missing data on smoking status. Future studies should investigate the risk of severe outcomes among active and passive smokers, the role that exposure to tobacco smoke constitutes among nonsmokers, the role of comorbidities in COVID-19 disease course, and health disparities experienced by disadvantaged groups.

Spatial Variation and Frequency Dependence of Lg Wave Attenuation With Site Response Correction Along the CCSE Array in Central California, US

AbstractWe estimate lateral Lg wave attenuation (Q) structure at four center frequencies (0.75, 1, 2 and 2.75 Hz) along the Central California Seismic Experiment array in western US crossing the San Andreas Fault and Central Valley. We take two steps in constructing the site‐response‐corrected Lg Q model: (a) we compute relative site responses at each station using the reverse two‐station method, and (b) we estimate Q values based on the two‐station method after removing the site term. Removal of the site response in the Q model allows to probe laterally varying Q properties at mid‐to‐lower crustal depths. Our model follows a power‐law frequency dependence as , reflecting the active tectonic setting and the presence of fluids in the region. A change in lithology from softer sediments near Pacific coast to harder basements near Sierra Nevada correlates well with the increasing trend of the Lg Q values towards east. Our laterally varying estimates at lower frequencies generally follow the variation of shear‐wave velocities at deeper crustal depth and Moho temperature, whereas those at higher frequencies mostly follow the shear‐wave velocity variation at shallow depth. Positive site responses obtained by reverse two‐station method are found at 34 stations out of total 46 stations examined, and their responses are mostly correlated with surficial lithology (i.e., sedimentary rocks) along the profile, rather than the thickness of the sediments. The site responses also exhibit a strong negative correlation to the VS30 data.

Effects of winter storms and oceanographic conditions on survival to weaning: a 37 year study of northern elephant seals on the Farallon Islands

Northern elephant seals Mirounga angustirostris were extirpated from California in the 19th century, and only in recent decades have they recolonized. A key demographic parameter underlying population viability is the survival of pups, from birth to weaning. We evaluated local factors acting directly on pup survival prior to weaning and basin-wide factors reflecting oceanic conditions which may impact maternal condition and behavior, using a 37 yr time series from 2 adjacent islands off central California: Southeast Farallon Island (SEFI) and West End Island (WEI). Mixed-effects logistic regression indicated that annual pup survival decreased with increasing frequency of extreme waves during January and February, which may inundate haulout locations when pups are present, and increased with the North Pacific Gyre Oscillation (NPGO) index, reflecting increased primary productivity. Moreover, the impact of extreme waves was manifest only for WEI, which may reflect a greater risk of inundation compared to SEFI. Annual pup survival was most highly correlated with NPGO values during the 6 mo period preceding and including arrival and the pupping period (fall and winter). Our findings suggest that favorable foraging conditions for females during the 4 mo prior to hauling out led to better maternal condition, which improved pup survival. Impacts of storm surges on pup survival is of concern since the frequency and severity of storms is expected to increase in the future. To support population recovery, we recommend studies consider demographic parameters such as recruitment of females to the Farallon breeding population and to adjacent coastal California colonies.

Otolith chemistry indicates age and region of settlement of immature shortspine thornyhead Sebastolobus alascanus in the eastern Pacific Ocean

Shortspine thornyhead Sebastolobus alascanus are widely distributed along the eastern Pacific coast and are assessed as a demographically homogeneous stock off the coasts of California, Oregon and Washington. The validity of this assumption has been questioned because data suggest complex ontogenetic movements. Otolith microchemistry applied to immature fish was used to determine the age of settlement and the population structure of S. alascanus. Samples were collected from 2011-2013 from bottom trawl surveys in 5 areas along the coasts of (1) Washington, (2) northern Oregon, (3) southern Oregon and northern California, (4) central California and (5) southern California. The Ba:Ca ratio, measured from the primordium to the margin of otoliths, corresponds to the pelagic and benthic phases of immature fish. This ratio decreased steadily before the formation of the first annulus and increased thereafter. Water masses along the bathymetric gradient mostly correlated with the distribution of otolith trace element (Mg:Ca, Ba:Ca) and stable isotope (δ18O and δ13C) ratios on the continental shelf. These results indicate that the population of immature fish belongs to 2 distinct groups, distributed north and south of Cape Mendocino. Accordingly, the performance of a k-nearest-neighbor classifier was highest when structured based on these 2 regions, with 94 and 69% cross-validated classification accuracy, respectively into the northern and southern groups. These results confirm that S. alascanus settle after nearly 1 yr of pelagic life and show that otolith chemistry can be used to test critical hypotheses regarding the migration and population structure of this species.

“Teaching students like me:” Bilingual authorization candidates, motivations, and California’s bilingual education renaissance

ABSTRACT Emerging from nearly two decades of language suppression wrought by Proposition 227, a Bilingual Education Renaissance is underway in California as new programs proliferate at a much faster clip than the state can produce certified bilingual teachers. California’s policy shift is built upon an officially stated view of bilingualism as a resource beneficial for student academic success and global economic competitiveness. While the stated goals of public policy are clear, less known is what motivates educators aspiring to serve these new programs and how these individuals have been personally affected by the language restrictions of Proposition 227. Through analysis of surveys and autobiographical writing collected from bilingual authorization candidates in Central California, we explore the motivations of these budding bilingual educators, compare and contrast these motivations to those of state policy, and examine in autobiographical detail their ethnolinguistic experiences. We find that bilingual certification candidates – in contrast to the explicit economic considerations of the state–are overwhelmingly driven by a sense of advocacy and personal identification with the ethnolinguistic experiences and struggles of emergent bilingual students. We discuss implications for public policy, candidate recruitment, and the design of program content that is supportive and leveraging of candidate ethnolinguistic experiences and assets.

Across-Shore Propagation of Subthermocline Eddies in the California Current System

AbstractThough subthermocline eddies (STEs) have often been observed in the world oceans, characteristics of STEs such as their patterns of generation and propagation are less understood. Here, the across-shore propagation of STEs in the California Current System (CCS) is observed and described using 13 years of sustained coastal glider measurements on three glider transect lines off central and southern California as part of the California Underwater Glider Network (CUGN). The across-shore propagation speed of anticyclonic STEs is estimated as 1.35–1.49 ± 0.33 cm s−1over the three transects, line 66.7, line 80.0, and line 90.0, close to the westward long first baroclinic Rossby wave speed in the region. Anticyclonic STEs are found with high salinity, high temperature, and low dissolved oxygen anomalies in their cores, consistent with transporting California Undercurrent water from the coast to offshore. Comparisons to satellite sea level anomaly indicate that STEs are only weakly correlated to a sea surface height expression. The observations suggest that STEs are important for the salt balance and mixing of water masses across-shore in the CCS.

Tidal restrictions in a central Californian estuarine system are associated with higher mean pH, but increased low-pH exposure

Coastal acidification is an emerging concern in estuaries impaired by nutrient pollution. In addition to rising levels of atmospheric CO2 which drives ocean acidification, high nutrient inputs to coastal areas can amplify heterotrophic metabolism, raise water column CO2 levels, and exacerbate pH declines. This study focuses on how a third anthropogenic stressor, tidal restriction, shapes effects of coastal acidification. Tidal restrictions associated with installation of gates that reduce tidal flow to a portion of an estuary are a common impact to coastal landscapes and can negatively affect water quality. This study examined pH in locations subject to varying levels of tidal restriction across a series of interconnected central California estuaries, whose waters are nutrient-impaired due to surrounding agriculture, and where 50% of the system is affected by tidal restrictions. Mean and variance of pH differed based on the level of tidal restriction. Sites lacking tidal restrictions had the lowest mean pH (7.98) but the least pH variance (0.07), and the most infrequent exposure to low pH (<7.0) conditions. In contrast, sites with minimal tidal exchange had the most exposure to low pH conditions, although mean pH levels were greater (8.08), because they also saw greater pH variance (0.46). Our results suggest that tidal restrictions alter pH levels and affect the resilience of estuaries to coastal acidification.

Reproduction, body condition, age, and growth of a large sandy intertidal bivalve, Tivela stultorum

The iconic Pismo clamTivela stultorum(Mawe, 1823) once supported a thriving commercial and recreational fishery in California, but populations have declined statewide in recent decades, in part due to overfishing. To manage and restore populations, fishery managers need accurate life history information, but critical data on reproductive cycles, maturity, and growth rates is either unknown or many decades old. This project aimed to (1) determine annual reproductive cycles and body condition of Pismo clams; (2) identify environmental drivers of reproduction and body condition; (3) determine size-age relationships among clams in California; and (4) estimate growth rates. Up to 70 clams mo-1were collected from Pismo Beach, CA, for histological analysis to determine reproductive stage, measure a body condition index, and estimate ages from shells. Additional clams and shells were collected from sites north and south of Point Conception to compare growth and age at legal size between these 2 major oceanographic zones. Data suggests that reproductive timing deviates only slightly from historical records, with clams spawning later in the year than decades ago. Body condition indices correlate with reproductive stage 3 Ripe, providing an inexpensive proxy to monitor Pismo clam reproduction. Growth was faster in warmer Southern California compared to Central California, but still substantially slower than historical estimates; we estimate that Pismo clams reach the current legal size (114 mm) in 11.1 yr, several years later than previous estimates. Collectively, these data are critical to improve and guide management decisions for this once-abundant species.

First report of genetic data from two invasive Watersipora (Bryozoa) species in the central California coast rocky intertidal

First report of genetic data from two invasive Watersipora (Bryozoa) species in the central California coast rocky intertidal

BUDBURST TIMING OF VALLEY OAKS AT HASTINGS RESERVATION, CENTRAL COASTAL CALIFORNIA

We studied the timing of budburst of valley oak (Quercus lobata Née) at Hastings Reservation, central coastal California. Similar to other taxa, budburst was advanced by warmer temperatures. Over the 30-year study period, however, there were no significant trends in either air temperature or the timing of budburst, except during the 2014–2016 drought, during which the earliest budburst dates were advanced. Several individual tree characteristics correlated with budburst timing, including access to ground water, soil available phosphorus, and elevation, the effects of which were in turn correlated with winter microclimatic conditions of individual trees. Budburst timing was significantly related to both subsequent acorn production and radial growth; trees leafing out on or near the population mean for the year experienced greater radial growth and produced larger acorn crops than trees leafing out earlier or later than the mean. Differences in acorn production were due to both differences in phenology among trees and plasticity in the phenology of individual trees across years, while differences in radial growth were primarily due to plasticity in individual tree phenology. Valley oak phenology exhibits considerable variability; the extent to which this plasticity will help this keystone California species adapt to future climate change remains to be seen.

Farm labor productivity and the impact of mechanization

AbstractThere is a chronic shortage of agricultural labor in the US. Although growers increasingly turn to guest‐worker programs to meet their labor needs, few regard immigrant workers as a viable long‐term solution. Many producers of labor‐intensive agricultural commodities regard mechanization as a clear long‐term solution, making the slow rate of adoption of mechanized harvesting equipment in the US an empirical puzzle. In this article, we demonstrate that wage‐setting farmers have an incentive to “overmechanize,” or employ more than the cost‐minimizing level of capital when capital and labor are substitutes, but “undermechanize” when labor and capital are technical complements. This outcome can cause agricultural labor problems to persist under complementarity. To assess the potential role of farm under investment in labor augmenting capital equipment, we examine labor market outcomes following the adoption of non‐autonomous harvesting aids on a large strawberry farm in Central California. We develop an econometric model of peer‐affected productivity that controls for the group performance of farm workers operating in crews and find that mechanical aids complement labor in strawberry production, a finding that helps explain not only the relative lack of mechanized harvesting in strawberry production but, more generally, the persistent productivity gap in agricultural industries. We examine the broader implications of our theory for the slow rate of adoption of mechanical harvesting technologies in US agriculture by comparing general wage trends across several labor‐intensive and non‐labor‐intensive industries in California.

Salmonella enterica Serovar Diversity, Distribution, and Prevalence in Public-Access Waters from a Central California Coastal Leafy Green-Growing Region from 2011 to 2016.

Prevalence and serovar diversity of Salmonella enterica were measured during a 5-year survey of surface waters in a 500-mi2 agricultural region of the Central California Coast. Rivers, streams, lakes, and ponds were sampled bimonthly resulting in 2,979 samples. Overall prevalence was 56.4% with higher levels detected in spring than in fall. Small, but significant, differences in prevalence were detected based on sample locations. Detection of Salmonella was correlated positively with both significant rain events and, in some environments, levels of generic Escherichia coli. Analysis of 1,936 isolates revealed significant serovar diversity, with 91 different serovars detected. The most common isolated serovars were S. enterica subsp. enterica serovars I 6,8:d:- (406 isolates, 21.0%, and potentially monophasic Salmonella Muenchen), Give (334 isolates, 17.3%), Muenchen (158 isolates, 8.2%), Typhimurium (227 isolates, 11.7%), Oranienburg (106 isolates, 5.5%), and Montevideo (78 isolates, 4%). Sixteen of the 24 most common serovars detected in the region are among the serovars reported to cause the most human salmonellosis in the United States. Some of the serovars were associated with location and seasonal bias. Analysis of XbaI pulsed field gel electrophoresis (PFGE) patterns of strains of serovars Typhimurium, Oranienburg, and Montevideo showed significant intraserovar diversity. PFGE pulsotypes were identified in the region for multiple years of the survey, indicating persistence or regular reintroduction to the region. IMPORTANCE Nontyphoidal Salmonella is among the leading causes of bacterial foodborne illness, and increasing numbers of outbreaks and recalls are due to contaminated produce. High prevalence and 91 different serovars were detected in this leafy green growing region. Seventeen serovars that cause most of the human salmonellosis in the United States were detected, with 16 of those serovars detected in multiple locations and multiple years of the 5-year survey. Understanding the widespread prevalence and diversity of Salmonella in the region will assist in promoting food safety practices and intervention methods for growers and regulators.

Seasonal drought and its effects on frog population dynamics and amphibian disease in intermittent streams

AbstractChytridiomycosis, caused by the pathogenic fungusBatrachochytrium dendrobatidis(Bd), has contributed to amphibian declines globally, but drivers of outbreaks vary locally. Here, we explore the role of drought in population and host‐disease dynamics of the endangered stream‐breeding foothill yellow‐legged frog (Rana boylii). In central California (USA) where severity of seasonal drought is increasing, we observed the non‐native, Bd‐tolerant and lentic‐adapted North American bullfrog (Lithobates catesbeianus) extend into streams when flood disturbance was minimal. Analysis of skin swabs revealed that prevalence and load of Bd infection among bullfrogs was low. Yet, among the native frogs, prevalence and load intensified as the seasonal drought progressed and surface flow became intermittent. When temperatures decreased in autumn and frogs concentrated at a reduced number of water points, we found dozens of dead foothill yellow‐legged frogs (2018–2019). Necropsies suggested chytridiomycosis as the likely cause of death. Despite recent lethal outbreaks, foothill yellow‐legged frog population abundance appeared resilient based on comparison to prior decades when no die‐offs were observed. Wet–dry mapping of the stream channel and retrospective analysis of hydrologic records revealed that the native frogs spawn away from perennial pools, a behaviour that may allow them to avoid bullfrogs and predatory fish. In an ecological trade‐off, tadpoles face the risk of the stream drying before metamorphosis. Fluctuations in population size thus corresponded to extremes of inter‐annual variation in streamflow that limit recruitment rather than disease outbreaks. We conclude that hydrologic constraints, which climate change may exacerbate, appear to override the stressors of non‐indigenous species and chytridiomycosis.

Influence of a Post-dam Sediment Pulse and Post-fire Debris Flows on Steelhead Spawning Gravel in the Carmel River, California

Spawning gravel scarcity is a limiting factor for successful recovery of federally-threatened anadromous fish like steelhead of central California. A BACI-experimental design using bed particle counts from 2013 through 2021 shows that spawning-sized gravel (32–90 mm) diminished downstream of the former San Clemente Dam site in 2017, following dam removal in 2015. High flows in 2017 transported a pulse of sand and fine-gravel that filled pools and runs throughout the river below the dam. The bed material in the 3 km closest to the dam remained too coarse for redds in riffles and too fine in pools and runs. Time-series bathymetric data of the Los Padres Dam reservoir located in the upper Carmel watershed shows that nearly all bed material (including spawning gravel) in the upper Carmel River watershed was recruited during wet winters that immediately followed expansive wildfires. We studied that effect in detail following the Carmel Fire of August 2020, which preconditioned the slopes adjacent to the Carmel River for debris flows. Our analysis of several fire-mediated debris flows in 2021 show that they contained virtually no mud and held approximately 45% spawning-sized gravel. Although the debris flows contained abundant spawning gravel, and several flow snouts terminated in the Carmel River, the material was dispersed downstream rather than forming bars and patches that could be used for steelhead nest building. The generally small volume of material in the flows relative to the size of the river channel and impediments to debris flow runout limited the contribution of spawning-size gravel to the river.

Principles and Practice of Investigating Buried Adobe Features with Ground-Penetrating Radar

Because so many ancestral populations, at various times, have lived within the constraints of earthen architectural technology, it has significant representation in building traditions across large temporal and geographic expanses. Adobe, known also as dagga, ferey, cob, and by other names, is a variant in which clays and other sediments are combined with organic materials and formulated into discrete construction components, often in communities of practice for which adobe recipes, preparation, and application are integral to daily intersections of home and community. For archaeologists, community partners, and interested publics who wish to learn more about it, a large portion of this architectural culture is no longer visible above the surface but is accessible through archaeology. Yet low impact sampling, such as probing and test excavation, rarely reveals adobe features. Ground-penetrating radar (GPR) allows a tantalizing and non-invasive perspective on subsurface adobe features; increasingly there is a buried structural landscape emerging at sites where adobe architecture prevailed. The case studies presented here from 18th and 19th century sites in central and southern California serve as a guide for further survey.