California Ecosystems Research Articles

Stakeholder mapping of precision weeding commercialization ecosystem in California

CONTEXTPrecision weeding, a sector of agricultural technology in which drones and/or automated weeders use chemical, mechanical, or thermal means to eradicate weeds, has moved from academic research settings to commercialization. Because of labor shortage pressures, the push to gain competitive advantages, and the environmental impacts of excessive chemical inputs, many California growers have been interested in adopting precision weeding technologies in their operations. OBJECTIVEUsing semi-structured qualitative interviews, this study investigated the viewpoints of three key stakeholder groups involved in the diffusion and adoption of precision weeding technologies: California growers, precision weeding startups, and agricultural technology venture capital firms. With the supplemental viewpoints of large agricultural firms and their corporate venture capital arms and government agencies, this study seeks to understand the compatible motivations between stakeholders, current collaborative models between stakeholders and their limitations, and the user journey for growers adopting precision weeding technology. METHODSWe conducted 17 semi-structured qualitative interviews with diverse stakeholders in the precision weeding sector to gather textual data and gain high data saturation. Data collection balanced rigorous criteria for participant selection with adaptive interview questions to ensure depth and relevance. The analysis procedure involved coding and thematic framework development, complemented by grounded theory for iterative data examination and stakeholder map creation for distilling cross-organizational insights and stakeholder dynamics. RESULTS AND CONCLUSIONSThe results indicated that compatible motivations include addressing current labor issues, reducing costs, and the potential of precision weeding to transform agriculture. Less cited but still popular motivations included having more weeding options, meeting specific field needs, and environmental sustainability. The individual and stakeholder group cognitive maps demonstrated that concerns such as startup longevity, the high expenses of precision weeding machinery, and some startups lacking a direct connection to growers commonly limit the growers' adoption of precision weeding technologies. SIGNIFICANCEThe procedure and cognitive mapping presented in this study can be applied to other emerging agtech technologies and ecosystems.

Understanding post‐fire vegetation recovery in southern California ecosystems with the aid of pre‐fire observations from long‐term monitoring

AbstractAimsPost‐fire vegetation recovery is often determined by the similarity of post‐burn with unburned sites because of a lack of in situ information on pre‐fire communities. The inclusion of pre‐fire data can help account for pre‐existing differences and explore recovery also in terms of return to pre‐fire conditions. We used long‐term monitoring data in coastal sage scrub and grasslands to: (a) examine vegetation cover recovery of different functional groups; and (b) determine whether vegetation composition in burned areas has recovered in 4 years after fire with burned to unburned and pre‐ to post‐fire comparisons.LocationOrange County, California, USA.MethodsWe analyzed long‐term vegetation monitoring (2007–2021) data from 39 grassland and 58 coastal sage scrub transects in southern California, including observations before and after the 2017 Canyon 2 fire. Linear mixed‐effect models were used to determine whether forb, grass, and shrub covers differed between burned and unburned sites while considering the effects of year and repeated monitoring. We used canonical analysis of principal coordinates to analyze vegetation composition based on burn status and time of sampling.ResultsWhereas vegetation cover in grassland recovered quickly, native vegetation cover in burned coastal sage scrub remained lowered 4 years after fire, though forb and non‐native grass cover were higher in some post‐fire years. Community composition in burned coastal sage scrub was still in recovery 4 years after fire when compared with unburned or pre‐fire composition. Although burned and unburned grassland differed after fire in dominant grass species, inclusion of pre‐fire data showed that this was a pre‐existing difference.ConclusionsCoastal sage scrub had not recovered pre‐fire vegetation cover and composition by 4 years after fire, whereas grassland cover rebounded quickly, albeit with shifts in composition over time; patterns that were detected only by having pre‐ and post‐fire data from long‐term monitoring efforts.

The urban lives of green sea turtles: Insights into behavior in an industrialized habitat using an animal-borne camera.

The cryptic and aquatic life histories of sea turtles have made them a challenging group to directly observe, leaving significant knowledge gaps regarding social behavior and fine-scale elements of habitat use. Using a custom-designed animal-borne camera, we observed previously undocumented behaviors by green turtles (Chelonia mydas) at a foraging area in San Diego Bay, a highly urbanized ecosystem in California, USA. We deployed a suction-cup-attached pop-off camera (manufactured by Customized Animal Tracking Solutions) on 11 turtles (mean straight carapace length = 84.0 ± 11.2 cm) for between 1 and 30.8 h. Video recordings, limited to sunlit hours, provided 73 h of total observation time between May 2022 and June 2023. We observed 32 conspecific interactions; we classified 18 as active, entailing clear social behaviors, as compared with 14 passive interactions representing brief, chance encounters. There was no evidence for agonistic interactions. The camera additionally revealed that green turtles consistently use metal structures within urban San Diego Bay. In seven instances, turtles exhibited rubbing behavior against metal structures, and we observed two examples of turtles congregating at these structures. High rates of intraspecific interaction exhibited relatively consistently among individuals provide a compelling case for sociality for green turtles in San Diego Bay, adding to a growing research base updating their historical label of "non-social." The frequent use of metal structures by the population, in particular the rubbing of exposed skin, has implications for behavioral adaptations to urban environments. Our study exemplifies the promise of technological advances (e.g., underwater and animal-borne cameras) for updating natural history paradigms, even for well-studied populations.

Investigating eco-evolutionary processes of microbial community assembly in the wild using a model leaf litter system.

Microbial communities are not the easiest to manipulate experimentally in natural ecosystems. However, leaf litter-topmost layer of surface soil-is uniquely suitable to investigate the complexities of community assembly. Here, we reflect on over a decade of collaborative work to address this topic using leaf litter as a model system in Southern California ecosystems. By leveraging a number of methodological advantages of the system, we have worked to demonstrate how four processes-selection, dispersal, drift, and diversification-contribute to bacterial and fungal community assembly and ultimately impact community functioning. Although many dimensions remain to be investigated, our initial results demonstrate that both ecological and evolutionary processes occur simultaneously to influence microbial community assembly. We propose that the development of additional and experimentally tractable microbial systems will be enormously valuable to test the role of eco-evolutionary processes in natural settings and their implications in the face of rapid global change.

Natural climate solutions provide robust carbon mitigation capacity under future climate change scenarios

Natural climate solutions (NCS) are recognized as an important tool for governments to reduce greenhouse gas emissions and remove atmospheric carbon dioxide. Using California as a globally relevant reference, we evaluate the magnitude of biological climate mitigation potential from NCS starting in 2020 under four climate change scenarios. By mid-century NCS implementation leads to a large increase in net carbon stored, flipping the state from a net source to a net sink in two scenarios. Forest and conservation land management strategies make up 85% of all NCS emissions reductions by 2050, with agricultural strategies accounting for the remaining 15%. The most severe climate change impacts on ecosystem carbon materialize in the latter half of the century with three scenarios resulting in California ecosystems becoming a net source of carbon emissions under a baseline trajectory. However, NCS provide a strong attenuating effect, reducing land carbon emissions 41–54% by 2100 with total costs of deployment of 752–777 million USD annually through 2050. Rapid implementation of a portfolio of NCS interventions provides long-term investment in protecting ecosystem carbon in the face of climate change driven disturbances. This open-source, spatially-explicit framework can help evaluate risks to NCS carbon storage stability, implementation costs, and overall mitigation potential for NCS at jurisdictional scales.

Predicting plant species climate niches on the basis of mechanistic traits

Abstract Improved estimation of climate niches is critical, given climate change. Plant adaptation to climate depends on their physiological traits and their distributions, yet traits are rarely used to inform the estimation of species climate niches, and the power of a trait‐based approach has been controversial, given the many ecological factors and methodological issues that may result in decoupling of species' traits from their native climate. For 107 species across six ecosystems of California, we tested the hypothesis that mechanistic leaf and wood traits can robustly predict the mean of diverse species' climate distributions, when combining methodological improvements from previous studies, including standard trait measurements and sampling plants growing together at few sites. Further, we introduce an approach to quantify species' trait‐climate mismatch. We demonstrate a strong power to predict species mean climate from traits. As hypothesized, the prediction of species mean climate is stronger (and mismatch lower) when traits are sampled for individuals closer to species' mean climates. Improved resolution of species' climate niches based on mechanistic traits can importantly inform conservation of vulnerable species under the threat of climatic shifts in upcoming decades. Read the free Plain Language Summary for this article on the Journal blog.

Evidence of exploitative competition between honey bees and native bees in two California landscapes.

Human-mediated species introductions provide real-time experiments in how communities respond to interspecific competition. For example, managed honey bees Apis mellifera (L.) have been widely introduced outside their native range and may compete with native bees for pollen and nectar. Indeed, multiple studies suggest that honey bees and native bees overlap in their use of floral resources. However, for resource overlap to negatively impact resource collection by native bees, resource availability must also decline, and few studies investigate impacts of honey bee competition on native bee floral visits and floral resource availability simultaneously. In this study, we investigate impacts of increasing honey bee abundance on native bee visitation patterns, pollen diets, and nectar and pollen resource availability in two Californian landscapes: wildflower plantings in the Central Valley and montane meadows in the Sierra. We collected data on bee visits to flowers, pollen and nectar availability, and pollen carried on bee bodies across multiple sites in the Sierra and Central Valley. We then constructed plant-pollinator visitation networks to assess how increasing honey bee abundance impacted perceived apparent competition (PAC), a measure of niche overlap, and pollinator specialization (d'). We also compared PAC values against null expectations to address whether observed changes in niche overlap were greater or less than what we would expect given the relative abundances of interacting partners. We find clear evidence of exploitative competition in both ecosystems based on the following results: (1) honey bee competition increased niche overlap between honey bees and native bees, (2) increased honey bee abundance led to decreased pollen and nectar availability in flowers, and (3) native bee communities responded to competition by shifting their floral visits, with some becoming more specialized and others becoming more generalized depending on the ecosystem and bee taxon considered. Although native bees can adapt to honey bee competition by shifting their floral visits, the coexistence of honey bees and native bees is tenuous and will depend on floral resource availability. Preserving and augmenting floral resources is therefore essential in mitigating negative impacts of honey bee competition. In two California ecosystems, honey bee competition decreases pollen and nectar resource availability in flowers and alters native bee diets with potential implications for bee conservation and wildlands management.

Reference genome of California walnut, Juglans californica, and resemblance with other genomes in the order Fagales.

Juglans californica, California walnut, is a vulnerable small tree that is locally abundant but restricted to woodland and chaparral habitats of Southern California threatened by urbanization and land use change. This species is the dominant species in a unique woodland ecosystem in California. It is one of two endemic California walnut species (family Juglandaceae). The other species, Northern California black walnut (J. hindsii), has been suggested controversially to be a variety of J. californica. Here, we report a new, chromosome-level assembly of J. californica as part of the California Conservation Genomics Project (CCGP). Consistent with the CCGP common methodology across ~150 genomes, we used Pacific Biosciences HiFi long reads and Omni-C chromatin-proximity sequencing technology to produce a de novo assembled genome. The assembly comprises 137 scaffolds spanning 551,065,703 base pairs, has a contig N50 of 30Mb, a scaffold N50 of 37Mb, and BUSCO complete score of 98.9%. Additionally, the mitochondrial genome has 701,569 base pairs. In addition, we compare this genome with other existing high quality Juglans and Quercus genomes, which are in the same order (Fagales) and show relatively high synteny within the Juglans genomes. Future work will utilize the J. californica genome to determine its relationship with the Northern California walnut and assess the extent to which these two endemic trees might be at risk from fragmentation and/or climate warming.

Vegetation type change in California’s Northern Bay Area: A comparison of contemporary and historical aerial imagery

The North Bay area of California is a populous and ecologically diverse area that has experienced significant changes in the past century, as well as a series of recent wildfires, after over a century of fire suppression practices. While much research has been conducted quantifying drivers and patterns of vegetation change in conifer-dominated ecosystems, and how such changes have influenced current trends in fire behavior, studies of similar focus and scale are rarer in non-conifer ecosystems, including mixed-hardwood forests or shrub-dominated ecosystems in central and coastal Northern California. This is despite the fact that ecosystems other than conifer forests make up the majority of area burned in California wildfires. As such, expanding research focused on patterns of large-scale vegetation change as a possible driver of this trend in this area is a priority. In this study, we sought to map the overall extent and patch sizes of broad vegetation classes across a 52,000 ha study area based on historical (1948) and contemporary (2014) aerial imagery and to investigate shifts in vegetation patterns, as well as potential pathways and drivers of detected changes. We classified vegetation types through segmenting our imagery into homogenous polygons, and assigning broad vegetation categories using a random forest algorithm. We then analyzed patterns of change using spatial statistics and conditional inference tree analyses. We detected a large increase (12%) in the relative landscape proportion and average patch size of the forest class, characterized by dense tree canopy cover. Woodlands and shrub patches were most susceptible to type change, with the majority (57% and 65%, respectively) of converted areas subsequently identified as denser forest stands. By contrast, herbaceous and forest patches were most persistent. We additionally found that disturbance history, specifically whether an area burned or not, and topographic variables, including elevation and aspect, were important influences on the likelihood of vegetation persistence, while slope and water availability were not. Historical aerial imagery, which provides fine resolution and accurate data over a large spatial scale, is a useful tool for detecting landscape-scale vegetation shifts in ecosystems where widespread vegetation monitoring was not common historically. The marked increase in dense forest we detected, specifically due to the conversion of large areas of shrub and woodland vegetation may correspond to higher surface and ladder fuel load and continuity, and potentially higher wildfire risk. Fuel reduction treatments typically implemented in conifer-dominated forests may also be warranted in these mixed hardwood forests. However, more research is needed to understand drivers of change in non-conifer-dominated ecosystems in California and how such change influences wildfire behavior.

Reference genome of the long-jawed orb-weaver, Tetragnatha versicolor (Araneae: Tetragnathidae).

Climate-driven changes in hydrological regimes are of global importance and are particularly significant in riparian ecosystems. Riparian ecosystems in California provide refuge to many native and vulnerable species within a xeric landscape. California Tetragnatha spiders play a key role in riparian ecosystems, serving as a link between terrestrial and aquatic elements. Their tight reliance on water paired with the widespread distributions of many species make them ideal candidates to better understand the relative role of waterways versus geographic distance in shaping the population structure of riparian species. To assist in better understanding population structure, we constructed a reference genome assembly for Tetragnatha versicolor using long-read sequencing, scaffolded with proximity ligation Omni-C data. The near-chromosome-level assembly is comprised of 174 scaffolds spanning 1.06 Gb pairs, with a scaffold N50 of 64.1 Mb pairs and BUSCO completeness of 97.6%. This reference genome will facilitate future study of T. versicolor population structure associated with the rapidly changing environment of California.

Annual biomass spatial data for southern California (2001-2021): Above- and belowground, standing dead, and litter.

Biomass estimates for shrub-dominated ecosystems in southern California have been generated at national and statewide extents. However, existing data tend to underestimate biomass in shrub vegetation types, are limited to one point in time, or estimate aboveground live biomass only. In this study, we extended our previously developed estimates of aboveground live biomass (AGLBM) based on the empirical relationship of plot-based field biomass measurements to Landsat NDVI and multiple environmental factors to include other vegetative pools of biomass. AGLBM estimates were made by extracting plot values from elevation, solar radiation, aspect, slope, soil type, landform, climatic water deficit, evapotranspiration, and precipitation rasters and then using a Random Forest model to estimate per-pixel AGLBM across our southern California study area. By substituting year-specific Landsat NDVI and precipitation data, we created a stack of annual above ground live biomass raster layers for each year from 2001 - 2021. Using these AGLBM data as a foundation, we developed decision rules to estimate belowground, standing dead, and litter biomass pools. These rules were based on relationships between AGLBM and the biomass of the other vegetative pools derived primarily from peer reviewed literature and an existing spatial dataset. For shrub vegetation types (our primary focus), rules were based on literature estimates by the post-fire regeneration strategy of each species (obligate seeder, facultative seeder, obligate resprouter). Similarly, for non-shrub vegetation types (grasslands, woodlands) we used literature and existing spatial datasets specific to each vegetation type to define rules to estimate the other pools from AGLBM. Using a Python language script that accessed ESRI raster GIS utilities, we applied decision rules to create raster layers for each of the non-AGLBM pools for the years 2001-2021. The resulting spatial data archive contains a zipped file for each year; each of these files contains four 32-bit tiff files for each of the four biomass pools (AGLBM, standing dead, litter, and below ground). The biomass units are g/m2 . We estimated the uncertainty of our biomass data by conducting a Monte Carlo analysis of the inputs used to generate the data. Our Monte Carlo technique used randomly generated values for each of the literature-based and spatial inputs based on their expected distribution. We conducted 200 Monte Carlo iterations, which produced percent uncertainty values for each of the biomass pools. Results showed, using 2010 as an example, mean biomass for the study area and percent uncertainty for each of the pools as: AGLBM (905.4 g/m2 , 14.4%); standing dead (644.9 g/m2 , 1.3 %); litter (731.2 g/m2 , 1.2 %); and belowground (776.2 g/m2 , 17.2 %). Because our methods are consistently applied across each year, the data produced can be used to inform changes in biomass pools due to disturbance and subsequent recovery. As such, these data provide an important contribution to supporting the management of shrub-dominated ecosystems for monitoring trends in carbon storage and assessing the impacts of wildfire and management activities, such as fuel management and restoration. There are no copyright restrictions on the data set; please cite this paper and the data package when using these data. This article is protected by copyright. All rights reserved.

The magnitude and pace of photosynthetic recovery after wildfire in California ecosystems

Wildfire modifies the short- and long-term exchange of carbon between terrestrial ecosystems and the atmosphere, with impacts on ecosystem services such as carbon uptake. Dry western US forests historically experienced low-intensity, frequent fires, with patches across the landscape occupying different points in the fire-recovery trajectory. Contemporary perturbations, such as recent severe fires in California, could shift the historic stand-age distribution and impact the legacy of carbon uptake on the landscape. Here, we combine flux measurements of gross primary production (GPP) and chronosequence analysis using satellite remote sensing to investigate how the last century of fires in California impacted the dynamics of ecosystem carbon uptake on the fire-affected landscape. A GPP recovery trajectory curve of more than five thousand fires in forest ecosystems since 1919 indicated that fire reduced GPP by [Formula: see text] g C m[Formula: see text] y[Formula: see text]([Formula: see text]) in the first year after fire, with average recovery to prefire conditions after [Formula: see text] y. The largest fires in forested ecosystems reduced GPP by [Formula: see text] g C m[Formula: see text] y[Formula: see text] (n = 401) and took more than two decades to recover. Recent increases in fire severity and recovery time have led to nearly [Formula: see text] MMT CO[Formula: see text] (3-y rolling mean) in cumulative forgone carbon uptake due to the legacy of fires on the landscape, complicating the challenge of maintaining California's natural and working lands as a net carbon sink. Understanding these changes is paramount to weighing the costs and benefits associated with fuels management and ecosystem management for climate change mitigation.

Ecological integrity of whitebark pine ecosystems in California’s national forests

Whitebark pine ( Pinus albicaulis) forest ecosystems in California are diverse and unique, yet their current status and condition are uncertain. Using a combination of geospatial and field plot data, we assessed patterns in the structure, composition, and health of whitebark pine ecosystems on national forests throughout the state of California to evaluate potential signs of declining ecosystem integrity. We found whitebark pine ecosystems to be structurally, compositionally, and functionally distinct among subregions of California, and all subregions displayed some evidence of declining ecological integrity. Whitebark pine forests in northern California exhibited signs of greater stand densification (Cascade–Klamath), potential encroachment by shade-tolerant conifer species (Cascade–Klamath and Warner Mountains), and increased tree mortality associated with mountain pine beetle outbreaks (Warner Mountains) than elsewhere in California. Whitebark pine stands in the Sierra Nevada showed signs of stand densification (central Sierra) and localized mountain pine beetle outbreaks (southern Sierra east). Notwithstanding these negative signs, much of the state’s whitebark pine ecosystems on national forestlands appear to be relatively healthy and intact compared to more northern latitudes. Active management may be required to restore whitebark pine ecosystems on national forests in California with declining integrity, including stands experiencing substantial stand densification, encroachment by shade-tolerant conifers, and mountain pine beetle outbreaks.

Drivers of California’s changing wildfires: a state-of-the-knowledge synthesis

Over the past four decades, annual area burned has increased significantly in California and across the western USA. This trend reflects a confluence of intersecting factors that affect wildfire regimes. It is correlated with increasing temperatures and atmospheric vapour pressure deficit. Anthropogenic climate change is the driver behind much of this change, in addition to influencing other climate-related factors, such as compression of the winter wet season. These climatic trends and associated increases in fire activity are projected to continue into the future. Additionally, factors related to the suppression of the Indigenous use of fire, aggressive fire suppression and, in some cases, changes in logging practices or fuel management intensity, collectively have produced large build-ups of vegetative fuels in some ecosystems. Human activities provide the most common ignition source for California’s wildfires. Despite its human toll, fire provides a range of ecological benefits to many California ecosystems. Given the diversity of vegetation types and fire regimes found in the state, addressing California’s wildfire challenges will require multi-faceted and locally targeted responses in terms of fuel management, human-caused ignitions, building regulations and restrictions, integrative urban and ecosystem planning, and collaboration with Tribes to support the reinvigoration of traditional burning regimes.

Herbivore Influence on Post-Fire California Sage Scrub Plant and Soil Microbial Assemblages

California sage scrub (CSS) is an endangered, shrub-dominated, southern California ecosystem type threatened by increasing fire frequencies and conversion to non-native grasslands. As CSS harbors a rich endemic flora and fauna and is critical for maintaining key ecosystem services; significant attention has been focused on understanding how many key factors (N-deposition, drought, and competition with non-natives) influence post-fire CSS recovery. Unfortunately, few studies have examined the role of herbivores. For five years, we investigated the influence of herbivores on post-fire CSS succession by annually surveying plant assemblages in control (herbivores allowed access) and experimental (herbivore excluded) plots at the Bernard Field Station following a fire in May 2017. We found that herbivores reduce the cover of both invasive grasses and native shrubs, and negatively impact Artemisia californica survivorship. Consequently, post-fire plant restoration efforts should not discount the effects of herbivores. While native forb cover was elevated in plots that permitted herbivores, plots near the fire edge experienced increased herbivory pressure and lower cover of most plants. Despite modifications in plant assemblages, we did not observe differences in soil microbe abundances, fungi assemblage structure, or nutrient concentrations. We suggest that restoration practitioners consider caging ‘shrub regeneration’ areas to facilitate post-fire CSS recovery.

Statistical evaluation of the similarity of characteristics in springs of the California Desert, United States

Desert ecosystems are an environment of climatic extremes, to which many forms of life have adapted. These systems are characterized by scarce water and often sparsely vegetated lands where ecological adaptation to arid conditions has its underpinnings in the universal dependency on water to support life. Understanding the ecohydrological similarity of springs in water-limited areas requires integration of multiple lines of evidence from diverse disciplines. A unique dataset of hydrological and ecological characteristics of Mojave and Sonoran Desert spring ecosystems in California has been developed, incorporating a wide range of spring conditions that enables a broad evaluation of similarity in ecohydrological characteristics across springs in the region. The lack of observed correlation between hydrologic and ecological parameters suggests that the springs in the California Desert each represent a somewhat unique ecosystem that has developed in relative isolation from the other springs. These results imply that because of the uniqueness of these desert ecosystems the idea of mitigation compensation or mitigation offset via replacement or substitution can never truly be achieved if/when these spring areas are impacted. Any ecosystem used as a replacement or substitution could not reasonably be expected to be similar in terms of the associated hydrologic and ecologic conditions to the ecosystem lost. While such offsets can represent a coarser view of replacements or substitution, the more specific conditions that support endemic and water-dependent biodiversity cannot be easily replaced or substituted.

Larval Thermal Tolerance of Kellet's Whelk (Kelletia kelletii) as a Window into the Resilience of a Wild Shellfishery to Marine Heatwaves

Marine heatwave (MHW) events are emerging as dominant and disruptive extreme disturbance events on the Pacific coast. These events are expected to have significant impacts on shellfish species and aquaculture operations. In general, thermal stress induced by MHW events has been documented to have impacts on the productivity and biodiversity of coastal marine ecosystems in California. Yet, there is limited understanding on how thermal stress will affect economically important shellfish species, especially at vulnerable early life stages. This study assessed the effect of high temperature stress that resembled recent local MHW conditions on the larval stages of the Kellet's whelk, Kelletia kelletii, an emerging seafood species from California temperate reefs. Adult whelks were collected at temperate reef sites in the Santa Barbara Channel, and larvae were sourced from egg capsules laid by adult whelks in the laboratory. Thermotolerance trials were determined for two stages of K. kelletii larvae: encapsulated veligers and veligers that had emerged from the capsules as hatchlings. During the trials, larvae were scored for two metrics: (1) mortality and (2) developmental abnormality. After exposure of larvae to a range of temperatures (15°C–37°C) in acute thermotolerance trials (1 h), the mortality of veligers and hatchlings occurred at similar temperatures. In contrast, temperatures that induced developmental abnormalities for both encapsulated veligers and hatchlings were lower than temperatures that caused mortality. And further, temperatures that induced abnormal development were different for the two stages. These results provide some of the first insights on effects of environmentally relevant MHW temperatures on larval forms of the Kellet's whelk, and suggest the potential decline of populations in situ in response to continued stress from local MHW events.

Impacts of livestock grazing on the probability of burning in wildfires vary by region and vegetation type in California

Wildfire activity has recently increased in California, impacting ecosystems and human well-being. California's rangelands are complex social-ecological systems composed of multiple ecosystems and the people who live and work in them. Livestock grazing has been proposed as a tool for reducing wildfire activity. Here, we explore how grazing affects wildfire at large spatial scales, assessing burn probability on rangelands with different grazing levels. We collected grazing data by surveying 140 large private landowners in three social-ecological regions: California's North Bay, Central Coast, and Central Valley and Foothills. Using pre-regression matching and mixed effects regression, we calculate the burn probability from 2001 to 2017 in points sampled from grazed and ungrazed properties in each region in grasslands, shrub/scrublands, and forests. We find that in the Central Coast and North Bay, annual burn probability decreases as stocking levels increase across all vegetation types, with reductions of 0.008–0.036. In the Central Valley and Foothills, the relationship is complex, with burn probability increasing over some grazing levels and variations in the effect of higher stocking densities. Our results indicate that livestock grazing may reduce annual burn probability in some regions and ecosystems in California, providing the first large-scale assessment of this relationship.

Relationship of Sphaeroma quoianum to sediment characteristics and invertebrate community

Many important wetland functions are tied to sediment dynamics, which are influenced by infaunal invertebrate communities. These communities are sensitive to changes in sediment structure and to colonization by non-native species. In a southern California salt marsh, the non-native isopod Sphaeroma quoianum has created dense networks of burrows within the marsh banks. Since this isopod increases erosion in many areas and can change local invertebrate communities, its possible contribution to habitat loss in this already-scarce southern California ecosystem is an important issue. To determine the relationship of S. quoianum to invertebrate community and sediment characteristics, three burrowed transects and one unburrowed transect were surveyed and sampled for invertebrate and sediment cores. This study tested the association between burrows and grain size distribution, sediment carbon content, respiration rates, and invertebrate community composition. Sphaeroma quoianum burrows were correlated with altered invertebrate community composition, decreased carbon content, and steep marsh bluffs. These results highlight the potential susceptibility of salt marsh habitat with steep edges to invasion by non-native species. These results also suggest that S. quoianum invasion of salt marsh habitats can alter native communities and ecosystem functions; thus, incipient invasions should be of concern to managers and ecologists alike.

Genomic data reveal local endemism in Southern California Rubber Boas (Serpentes: Boidae, Charina) and the critical need for enhanced conservation actions

The mountains of southern California represent unique, isolated ecosystems that support distinct high-elevation habitats found nowhere else in the area. Analyses of several moisture-dependent species across these sky-islands indicate they exist as locally endemic lineages that occur across these fragmented mountains ranges. The Rubber Boa is a semi-fossorial snake species that is widely distributed in the cooler and more moist ecoregions regions of western North America, including isolated populations across southern California mountain ranges. We developed a genomic and ecological dataset to examine genetic diversity within Rubber Boas and to determine if the endemic Southern Rubber Boa represents a distinct lineage. We quantified current and future habitat suitability under a range of climate change scenarios, and discuss the possible environmental threats facing these unique montane isolates. Our results support four major lineages within Rubber Boas, with genetic breaks that are consistent with biogeographic boundaries observed in other co-distributed, cool-temperature, moisture adapted species. Our data support previous studies that the Southern Rubber Boa is an independent evolutionary unit and now includes multiple locally endemic sky-island populations, restricted to isolated mountain tops and ranges across southern California. Analyses of future habitat suitability indicate that many of these sky-island populations will lose most of their suitable habitat over the next 70 years given predicted increases in drought, rising temperatures, and wildfires. Collectively these data emphasize the critical conservation needs of these montane ecosystems in southern California under current and projected climate change conditions.