Geology topics

Research about California, Nevada

Source-linked reports with geographic coverage including California, Nevada.

At least 19 recordsLinked to original sources

USGS2026

Abundant ticks but limited Borrelia spp. pathogens in Mojave desert tortoise habitat

Ornithodoros ticks, a genus of soft ticks in the family Argasidae, occur worldwide including throughout deserts in the Southwestern United States. In the Mojave Desert, Ornithodoros parkeri and O. turicata are common ectoparasites of Mojave desert tortoises ( Gopherus agassizii ). These two tick species are vectors of Borrelia spp. that cause tick-borne relapsing fever (TBRF) in people. However, the distribution of O. parkeri and O. turicata and TBRF group Borrelia infection prevalence remain poorly known in the Mojave Desert. These ticks are commonly found in desert tortoise burrows. In this study, 1165 ticks were collected in the Mojave Desert, 1164 of those ticks were identified as belonging to the genus Ornithodoros, while the remaining tick was an Otobius species. We used morphologic characteristics and molecular genetic analysis to identify ticks as O. parkeri and O. turicata . Twenty-two of the 1165 tick samples tested positive for TBRF group Borrelia, five of which could be sequenced and were identified as Borrelia turicatae . This study sheds light on the distributions of tick species and pathogens in an understudied ecosystem, the Mojave Desert, and identifies group Borrelia as a potential risk factor in Mojave desert tortoise habitat.

California, Nevada↗

USGS2026

Effects of oiling common raven nests on ravens and greater sage-grouse in sagebrush ecosystems

Common ravens ( Corvus corax ; ravens) are generalist avian predators whose populations have rapidly increased across North America, concomitant with anthropogenic development. Raven populations are bolstered by anthropogenic food and nesting resources in areas outside of their historical range and are impactful predators for many prey species of conservation concern, including greater sage-grouse ( Centrocercus urophasianus ; sage-grouse), primarily through reductions in sage-grouse nest survival. Previous research suggests that coating developing raven eggs in non-toxic oil, a form of egg-addling, positively affects sensitive prey species because the nesting ravens no longer need to provision for young, and thereby forage less. We sought to understand the effects of oiling raven eggs on raven population density and reproductive success, as well as nest survival and population growth rate of co-occurring populations of sage-grouse. By evaluating oil-treated, control, and sham-treated (applied water rather than oil) raven nests in a before-after-control-impact (BACI) research study design, we found that application of oil to raven eggs reduced raven egg hatchability by 94.5% and reduced raven densities at treatment sites relative to control sites. Sage-grouse nest survival probabilities more than doubled at egg-oiled treatment sites, resulting in a relative increase of 93.0% at treatment sites relative to control sites over the same period of inference. Finally, estimated abundances of sage-grouse increased at oil-treated sites by 44% relative to controls following oil treatments of raven eggs, also measured in a BACI framework. Oiling of raven eggs had strong and immediate impacts on co-occurring populations of sage-grouse and ravens.

California, Nevada↗

USGS2026

Changes in spatial distribution and abundance together determine potential for population persistence for greater sage-grouse

Aim Population ecologists often focus on changes in the distribution and abundance of wildlife species, which are useful for trend analyses and status assessments. However, rarely are these responses evaluated simultaneously for a single species, despite their unique contributions to fully assess a species' viability. For example, focusing solely on total abundance can mask important losses in overall distribution within a metapopulation structure that may contribute to long-term population instability that results from the extirpation of small peripheral populations. Location Bi-State region of Nevada and California, USA. Methods We simultaneously evaluated changes in population abundance and distribution for greater sage-grouse (hereafter sage-grouse; Centrocercus urophasianus ) within the Bi-State Distinct Population Segment (DPS), a genetically distinct and isolated population straddling the border of Nevada and California. We combined population counts, demographic data, and information on space use from marked individuals to evaluate changes in population distribution and abundance over three time periods that corresponded to the three most recent population nadirs (1995–2019, 2002–2019 and 2008–2019). Results The Bi-State DPS exhibited evidence of ~1.2%–2.5% declines annually, over the short/medium-term (1995–2019; λ^ = 0.987, 95% CRI: 0.970–0.999), short-term (2002–2019; λ^ = 0.975, 95% CRI: 0.963–0.985) and recent-term (2008–2019; λ^ = 0.988, 95% CRI: 0.973–1.001). Since 1995, the spatial distribution of sage-grouse abundance in the Bi-State DPS shifted amongst subpopulations, with peripheral subpopulations suffering the largest declines. Main Conclusions Gains in abundance and distribution amongst expanding subpopulations did not offset losses in the remaining subpopulations, with a net loss in occupied distribution of 156 km 2 since 1995. Reductions in spatial distribution could have implications for metapopulation persistence as peripheral populations become more vulnerable to stochastic events, which would not have been apparent from the evaluation of overall metapopulation abundance on its own.

California, Nevada↗

USGS2026

Insights into Mountain Pass carbonatite formation from in-situ sulfur isotopes and geochemistry of sulfate and sulfide minerals

The Mountain Pass carbonatite stock hosts a world-class rare earth element deposit and may be classified as a carbonate-sulfate igneous rock, as it contains on average > 50 volume percent carbonate minerals and 20 to 30 volume percent sulfate minerals. The sulfates range in composition from barite to celestine and locally occur with sparse sulfide minerals. We investigate the origin of sulfur enrichment and the occurrence of sulfur-bearing minerals in the Mountain Pass carbonatite with in-situ sulfur isotope and mineral chemistry. Barite cores with δ 34 S of 1 to 3‰ do not coexist with sulfides, whereas celestine rims with δ 34 S of > 3‰ are associated with sulfides with δ 34 S < -10‰. We propose a model in which sulfur-bearing sediments were subducted during episodes of plate convergence in the Mojave Province that preceded Mountain Pass magmatism. Metasomatism of the overlying mantle by melts derived from the subducted sediments generated an unusually carbon- and sulfur-rich source to yield carbonatite magmas. Sulfur from primary carbonatite magmas and ~ 1 to 7% sulfur from subducted sediment melts yielded a slightly enriched δ 34 S composition (relative to depleted mantle δ 34 S of -1‰) for early crystallizing barite. Celestine rims on magmatic barite cores formed at low, hydrothermal temperatures (< 350 °C) based on S isotope thermometry for equilibrium celestine-galena and celestine-pyrite pairs. The sparse sulfides in the carbonatite stock are not in equilibrium with the primary barite cores and therefore do not permit S isotope thermometry estimates of magmatic temperatures. The S/Se ratios of sulfide minerals (> 3,400) typically exceed primitive mantle values (S/Se of 3,340), also consistent with their derivation from hydrothermal fluids. Trace occurrences of sulfide and sulfate minerals in alkaline silicate stocks related to the carbonatite stock have similar δ 34 S compositions and yield similarly low formation temperatures, suggesting regionally extensive and chemically similar sulfur-bearing hydrothermal fluids that imparted lithologically diverse rocks with a consistent sulfur isotope fingerprint.

California, Nevada↗

USGS2026

Geologic map of the Sierra Nevada, California and western Nevada

THE GEOLOGIC MAP OF THE SIERRA NEVADA is a core component of the Sierra Nevada Earth Science Atlas, which also includes geophysical, neotectonic, economic, and geochronologic data. The map illustrates the distribution of geologic units across the Sierra Nevada and related adjacent areas. Geologic units are grouped by type and age into three categories: Principally Paleozoic and Mesozoic metasedimentary and metavolcanic wall rocks, most of which are grouped into terranes; Paleozoic and Mesozoic plutons and intrusive suites, which intrude the wall rocks and form the core batholith of the range; and Late Cretaceous and Cenozoic sedimentary and volcanic rocks and surficial deposits that unconformably overlap the older units. Related rock units were combined and simplified for presentation at a scale of 1:400,000, as shown in the list of map units and associated correlation of map units (Plate 1B) and description of map units (Appendix A). Tectonic faulting, folding and uplift have overprinted the rocks and have strongly influenced the spatial distribution of units and the distinct morphology of the Sierra Nevada as we see it today. The Atlas is the result of collaborative work by scientists and mapmakers from the California Geological Survey and the U.S. Geological Survey. The Atlas was originally envisioned by the late geologist Warren Nokleberg (1939-2021), who contributed much to the initial geologic map compilation

California, Nevada↗

USGS2025

The influence of mountain streamflow on nearshore ecosystem metabolism in a large, oligotrophic lake across a drought and a wet year

The influence of streamflow can be highly heterogeneous around lake edges, making it challenging to predict how benthic productivity in the littoral zone responds to hydroclimatic change. The degree to which streamflow affects nearshore productivity varies as a function of catchment characteristics, internal lake morphometry, and processes. This study investigates the relative influence of streamflow on nearshore metabolism (e.g., gross primary productivity [GPP], ecosystem respiration [ER], and net ecosystem productivity [NEP]) for shores with large, small, or no stream inflows (four locations across two shores) during two contrasting water years (one drought and one wet) in Lake Tahoe (Nevada/California, USA). Using Bayesian structural equation modeling, we found streamflow decreased water temperature, benthic light, and GPP across both years. Compared to the drought year, the subsequent wet year had 54% higher annual streamflow, 37% less light, and lower NEP at locations with large or small inflows (39% Δ −0.32 mmol O₂ m −3 d −1% and 49% Δ −1.19 mmol O₂ m −3 d −1 , respectively). During the wet year, we observed a 68% increase in the negative association between streamflow and nearshore GPP at the large inflow and a 62% decrease in the positive association between streamflow and GPP at the small inflow. This work demonstrates how oligotrophic littoral productivity varies across shorelines and in response to hydrological conditions, with streamflow and precipitation exerting contrasting effects depending on the proximity to inflowing streams. Our results suggest future lake responses to climate volatility depend on spatial and temporal hydrologic connectivity to catchments and upland processes.

California, Nevada↗

USGS2025

Leveraging wildfire to augment forest management and amplify forest resilience

Successive catastrophic wildfire seasons in western North America have escalated the urgency around reducing fire risk to communities and ecosystems. In historically frequent-fire forests, fuel buildup as a result of fire exclusion is contributing to increased fire severity. The probability of high-severity fire can be reduced by active forest management that reduces fuels, prompting federal and state agencies to commit significant resources to increase the pace and scale of fuel reduction treatments. However, lower severity areas of wildfires also have the potential to act as “treatments,” and even catastrophic fires with large areas of high severity can still have substantial areas of lower severity fire that may be improving forest conditions locally. We quantified active management and wildfire severity across yellow pine and mixed conifer (YPMC) forests in the Sierra Nevada of California over a 22-year period (2001–2022). We did not detect increases in the area treated through time, but the area of beneficial wildfire (low to moderate severity) increased substantially, exceeding active treatment area in 8 of 22 years. Overall, beneficial wildfire treated ~17% more area than all treatments combined, and roughly four times more area than fire-related treatments alone. We then used disturbance history to evaluate resistance to high-severity wildfire and forest loss across the YPMC range. Of the 2.3 million ha YPMC of forests in 2001, 20% lost mature forests due to high-severity fire by 2022, which is nearly half of all YPMC area burned. Most of the landscape (47%) remains at risk of high-severity fire because it had no restorative disturbances, but 33% of the study area has some level of resistance to high-severity wildfire. In these areas, resistance will need to be enhanced and maintained over time via active management or managed wildfire, but these treatment needs will likely outpace capacity even under optimistic implementation scenarios. Given limited resources for implementing active management and the likelihood of a more fiery future, incorporating beneficial wildfire into landscape-level treatment planning has the potential to amplify the impact of active management treatments.

California, Nevada↗

USGS2025

Limited directional change in mountaintop plant communities over 19 years in western North America

Plant communities on mountain summits are commonly long-lived, cold-adapted perennials with low dispersal ability. These characteristics in tandem with limited area to track suitable conditions make these mountain communities potentially highly vulnerable to climate change, and indicators of climate change impacts. We investigated temporal changes in plant communities on 29 arid mountain summits across eight study regions in California and Nevada, USA, over 19 years. We analyzed community dynamics in terms of species richness, turnover, gain and loss of functional groups, and relative abundance of functional groups. First, across all summits and regions, we found no change in species richness over time. Second, there was relatively high species turnover (21.7%) between the five-year survey intervals, but turnover was not significantly different from random expectation. Within functional groups, forbs had the greatest proportion of gains and cushions had the greatest proportion of losses. Third, qualitative abundance categories presented a small but consistent signal of decrease in the relative abundance of cushions, graminoids, and shrubs/trees over the study period. Across a broad geographic scale and nearly two decades, community patterns were widely similar, suggesting that climate change has not impacted local colonization or extirpation of mountaintop species in this arid region. These findings support observed differences in response to climate change between temperature-limited and water-limited regions globally, and highlight the lagged and variable nature of high-elevation systems. Our findings fill a major data gap on alpine plant community responses to climate change in the western United States and bolster the importance of long-term ecological monitoring with rapid climate change.

California, Nevada↗

USGS2025

Integrating multiple indices of habitat quality to inform habitat management for a sagebrush indicator species

Robust science is needed to inform national resource management and policy decisions. Predictive species habitat maps are frequently employed in conservation decision-making but are often based on a single metric representing habitat quality. We outlined a framework that combines multiple spatially explicit indices of potential habitat quality that could be used to identify and prioritize habitat management areas, using the greater sage-grouse ( Centrocercus urophasianus ; hereafter sage-grouse) as an example species. Due to large-scale changes in sagebrush ecosystems, sage-grouse have suffered significant population declines in recent decades and have become key to land management plans throughout the western United States, where comprehensive habitat maps are crucial to effective conservation efforts. We evaluated habitat selection and survival patterns of sage-grouse across six distinct annual life stages and seasons to generate predictive habitat map surfaces, mapped the distribution of current occupancy, and combined maps of potential selection and survival patterns with space use and occupancy indices to delineate example habitat management categories. Our approach facilitates identification of priority areas to target for habitat preservation and areas where anthropogenic impacts could occur with likely minimal impact to the species. Overall, by combining indices representing selection, survival, and current occupancy, we provide a framework to allow for a flexible and targeted management approach that could be adapted to a wide variety of species.

California, Nevada↗

USGS2024

Linking resource selection to population performance spatially to identify species' habitat across broad scales: An example of greater sage-grouse in a distinct population segment

Management decisions often focus on the habitat selection of marked individuals without considering the contribution to demographic performance in selected habitats. Because habitat selection is not always adaptive, understanding the spatial relationship between habitat selection and demographic performance is critical to management decisions. Mapping both habitat selection and demographic performance for species of conservation concern can help guide population-scale conservation efforts. We demonstrate a quantitative approach to differentiate areas supporting selection and survival at large spatial extents. As a case study, we applied this approach to greater sage-grouse ( Centrocercus urophasianus ; hereafter, sage-grouse), an indicator species for sagebrush ecosystems. We evaluated both habitat selection and survival across multiple reproductive life stages (nesting, brood-rearing) in the Bi-State Distinct Population Segment, a genetically distinct and geographically isolated population of sage-grouse on the southwestern edge of the species' range. Our approach allowed us to identify both mismatches between selection and survival and trade-offs between reproductive life stages. These findings suggest resource demands vary across time, with predation risk being a dominant driver of habitat selection during nesting and early brood-rearing periods when chicks are smaller and flightless, whereas access to forage resources becomes more important during late brood rearing when resources become increasingly limited. Moving beyond identifying and managing habitat solely based on species occupancy or use by incorporating demographic measures allows managers to tailor actions to their specific goals; for example, protections of areas that support high selection and high survival and restoration actions focused on increasing survival in areas of high selection and low survival.

California, Nevada↗

USGS2024

Status of greater sage-grouse in the Bi-State Distinct Population Segment—An evaluation of population trends, habitat selection, and efficacy of conservation actions

Preface This study was completed to provide timely scientific information regarding greater sage-grouse population trends, habitat selection, and the efficacy of previous conservation actions implemented to benefit the Bi-State Distinct Population Segment (DPS). Specifically, we provide these analyses to inform the current (2024) status review and pending listing decision for the DPS being undertaken by the U.S. Fish and Wildlife Service. These findings provide updated, detailed, and comprehensive information regarding the status of a geographically isolated and genetically distinct population of a species of high conservation concern and their habitat. Importantly, this report also provides information on the efficacy of previously implemented conservation actions targeting the Bi-State DPS in a framework that is transferable throughout the species’ range.

California, Nevada↗

USGS2024

From pixels to riverscapes: How remote sensing and geospatial tools can prioritize riverscape restoration at multiple scales

Prioritizing restoration opportunities effectively across entire riverscape networks (i.e., riverine landscape including floodplain and stream channel networks) can be difficult when relying on in-channel, reach-scale monitoring data, or watershed-level summaries that fail to capture riverscape heterogeneity and the information necessary to implement restoration actions. Leveraging remote sensing and geospatial tools to develop spatially continuous information across nested hierarchical scales may support increased understanding of local riverscape reaches in their broader network context. Using riparian (vegetation) and geomorphic (elevation) indicators to assess status of riverscape health, along with a measure of restoration capacity (valley bottom area), could be adapted to fit specific management goals related to riverscape restoration. Frameworks using remotely sensed vegetation and elevation data to prioritize restoration continuously across riverscapes at restoration-relevant, reach-scales may uphold the ecosystem services provided by riverscapes. By incorporating local knowledge and identifying caveats for using these datasets, continuous inferences can be applied at network scales (watershed to regional extent and reach-scale resolution) to prioritize restoration over a wide variety of ecoregions.

California, Nevada↗

USGS2024

Cooperative conservation actions improve sage-grouse population performance within the Bi-State Distinct Population Segment

Developing a robust monitoring framework that integrates efficacy assessments of cooperative conservation and restoration actions in relation to population viability is critical for successful long-term recovery of target ecosystems and species. However, often it is difficult to quantify conservation action efficacy because of the complex, dynamic nature of ecosystem processes and practical limitations associated with assessing target species’ population dynamics. Here, we present an analytical framework that allows for quantification of conservation action efficacy using greater sage-grouse ( Centrocercus urophasianus ; hereafter, sage-grouse) within the Bi-State Distinct Population Segment which borders Nevada and California. This framework utilizes web-based repositories of conservation efforts carried out in sagebrush ecosystems and readily fits within contemporary sagebrush conservation design strategies. We employed a state-space model within a Bayesian framework to estimate abundance (N) as inputs for a progressive change before-after-control-impact paired series (BACIPS) design. Count data from 57 leks (monitored between 2003–2021) coupled with 85 unique actions (initiated between 2012–2019) provided clear evidence that conservation actions increased population abundance, on average, by 4.4% annually across the study area, resulting in a 37.4% cumulative increase since 2012. Population gains varied by the type of conservation action and according to the number of lag years following its implementation.

California, Nevada↗

USGS2024

Statistical analysis of Lake Tahoe secchi depth data

Secchi depth measurements in Lake Tahoe have been collected at a Long-Term Profile (LTP) monitoring site since 1968. Periodic updates in Secchi trend analysis are needed to understand changes in the long-term record, changes in seasonal pattern, and to provide insight into the progress of restoration efforts in improving lake clarity. As such, this analysis is intended to evaluate the long-term and seasonal clarity conditions by updating the analysis by Jassby and others, (1999) and to demonstrate the use of statistical measures as metrics for comparing ongoing monitoring data (Watanabe, 2024).

California, Nevada↗

USGS2023

Move it or lose it: Predicted effects of culverts and population density on Mojave desert tortoise (Gopherus agassizii) connectivity

Roadways and railways can reduce wildlife movements across landscapes, negatively impacting population connectivity. Connectivity may be improved by structures that allow safe passage across linear barriers, but connectivity could be adversely influenced by low population densities. The Mojave desert tortoise is threatened by habitat loss, fragmentation, and population declines. The tortoise continues to decline as disturbance increases across the Mojave Desert in the southwestern United States. While underground crossing structures, like hydrological culverts, have begun receiving attention, population density has not been considered in tortoise connectivity. Our work asks a novel question: How do culverts and population density affect connectivity and potentially drive genetic and demographic patterns? To explore the role of culverts and population density, we used agent-based spatially explicit forward-in-time simulations of gene flow. We constructed resistance surfaces with a range of barriers to movement and representative of tortoise habitat with anthropogenic disturbance. We predicted connectivity under variable population densities. Simulations were run for 200 non-overlapping generations (3400 years) with 30 replicates using 20 microsatellite loci. We evaluated population genetic structure and diversity and found that culverts would not entirely negate the effects of linear barriers, but gene flow improved. Our results also indicated that density is important for connectivity. Low densities resulted in declines regardless of the landscape barrier scenario (> 75% population census size, > 97% effective population size). Results from our simulation using current anthropogenic disturbance predicted decreased population connectivity over time. Genetic and demographic effects were detectable within five generations (85 years) following disturbance with estimated losses in effective population size of 69%. The pronounced declines in effective population size indicate this could be a useful monitoring metric. We suggest management strategies that improve connectivity, such as roadside fencing tied to culverts, conservation areas in a connected network, and development restricted to disturbed areas.

California, Nevada↗

USGS2023

Wildfire immediately reduces nest and adult survival of greater sage-grouse

Wildfire events are becoming more frequent and severe on a global scale. Rising temperatures, prolonged drought, and the presence of pyrophytic invasive grasses are contributing to the degradation of native vegetation communities. Within the Great Basin region of the western U.S., increasing wildfire frequency is transforming the ecosystem toward a higher degree of homogeneity, one dominated by invasive annual grasses and declining landscape productivity. Greater sage-grouse ( Centrocercus urophasianus ; hereafter sage-grouse) are a species of conservation concern that rely on large tracts of structurally and functionally diverse sagebrush ( Artemisia spp.) communities. Using a 12-year (2008–2019) telemetry dataset, we documented immediate impacts of wildfire on demographic rates of a population of sage-grouse that were exposed to two large wildfire events (Virginia Mountains Fire Complex—2016; Long Valley Fire—2017) near the border of California and Nevada. Spatiotemporal heterogeneity in demographic rates were accounted for using a Before-After Control-Impact Paired Series (BACIPS) study design. Results revealed a 40% reduction in adult survival and a 79% reduction in nest survival within areas impacted by wildfires. Our results indicate that wildfire has strong and immediate impacts to two key life stages of a sagebrush indicator species and underscores the importance of fire suppression and immediate restoration following wildfire events.

California, Nevada↗

USGS2023

Linear and landscape disturbances alter Mojave desert tortoise movement behavior

Introduction: Animal movements are influenced by landscape features; disturbances to the landscape can alter movements, dispersal, and ultimately connectivity among populations. Faster or longer movements adjacent to a localized disturbance or within disturbed areas could indicate reduced habitat quality whereas slower or shorter movements and reduced movements may indicate greater availability of resources. The Mojave desert tortoise ( Gopherus agassizii ) is a threatened species that is challenged by anthropogenic disturbances. Methods: We studied tortoise movements using Global Positioning System (GPS) loggers at multiple sites in the Mojave Desert of Nevada and California. Tortoises at our sites encountered localized, linear human infrastructure, including paved roads, dirt roads, and fences, as well as landscape-scale disturbances [wildfire, off highway vehicle use (OHV), livestock grazing area]. We fit two-state (moving and encamped) Hidden Markov models to GPS logger data to infer how tortoise movement behavior relates to anthropogenic and natural features. Results: We found that temporal covariates, individual-level random effects (intercepts), and sex best explained state transition probability in all sites. We compared relationships between tortoise movement and linear disturbances, which varied depending on site and context. Tortoises made longer movements within the OHV recreation area, near most dirt roads, and near a low-traffic paved road, indicating that tortoises avoid these habitat disturbances. Conversely, tortoises made shorter movements in areas of higher slope and near highways, suggesting that these features may restrict movement or provide resources that result in prolonged use (e.g., forage or drinking locations). Tortoises that encountered fences around utility-scale solar installations were more active and made longer movements near fences, indicative of pacing behavior. Discussion: These results provide insight into how different disturbances alter tortoise movement behavior and modify tortoise habitat use, providing information that can be used to manage tortoise habitat.

California, Nevada↗

USGS2023

Growth, drought response, and climate-associated genomic structure in whitebark pine in the Sierra Nevada of California

Whitebark pine ( Pinus albicaulis Engelm.) has experienced rapid population declines and is listed as threatened under the Endangered Species Act in the United States. Whitebark pine in the Sierra Nevada of California represents the southernmost end of the species' distribution and, like other portions of its range, faces threats from an introduced pathogen, native bark beetles, and a rapidly warming climate. Beyond these chronic stressors, there is also concern about how this species will respond to acute stressors, such as drought. We present patterns of stem growth from 766 large (average diameter at breast height >25 cm), disease-free whitebark pine across the Sierra Nevada before and during a recent period of drought. We contextualize growth patterns using population genomic diversity and structure from a subset of 327 trees. Sampled whitebark pine generally had positive to neutral stem growth trends from 1970 to 2011, which was positively correlated with minimum temperature and precipitation. Indices of stem growth during drought years (2012 to 2015) relative to a predrought interval were mostly positive to neutral at our sampled sites. Individual tree growth response phenotypes appeared to be linked to genotypic variation in climate-associated loci, suggesting that some genotypes can take better advantage of local climatic conditions than others. We speculate that reduced snowpack during the 2012 to 2015 drought years may have lengthened the growing season while retaining sufficient moisture to maintain growth at most study sites. Growth responses may differ under future warming, however, particularly if drought severity increases and modifies interactions with pests and pathogens.

California, Nevada↗