Sierra Nevada Foothills Research Articles

Using iNaturalist presence data to produce suitability maps for Triatoma protracta, T. rubida and T. recurva in the American Southwest, Texas and northern Mexico, to identify potential transmission zones of Chagas disease.

There are 11 species of triatomines in the USA, with seven reported in the American Southwest. These species are capable of transmitting Trypanosoma cruzi, the etiological agent of Chagas disease, but are generally sylvatic and rarely infect humans in the USA. iNaturalist is one of the most popular citizen science data portals, where users record encounters with any individual organism. As of November 2023, iNaturalist reported 722 confirmed triatomine observations in the American Southwest. Maximum entropy ecological niche modelling and bioclimatic environmental variables were used to predict zones of highest human-triatomine interaction. Models fit well for Triatoma protracta (0.85), T. rubida (0.94), and T. recurva (0.96). Precipitation in the warmest quarter was most predictive of T. protracta presence, while precipitation in the driest quarter was most predictive of T. rubida and T. recurva. Locations identified in the American Southwest with highest potential for human-triatomine interaction, and potential T. cruzi transmission, were coastal California, the Sierra Nevada foothills, southern Arizona and border areas of northern Mexico. Study findings can be used for targeted surveillance efforts to address the paucity of contemporary information regarding triatomine species diversity and geographical and ecological associations in the American Southwest.

Varying degrees of human-animal interaction elicit weak evidence of a temporally stable behavioral trait in rangeland breeding ewes.

Coherent patterns of inter-related behaviors that occur across time and contexts, also known as personality or consistent individual differences (CIDs), are important to identify among livestock as they carry valuable information for selective breeding purposes. Repeated testing is necessary to reveal behavioral patterns, yet temporal stability of behavioral traits is often assumed. In this study, three human-animal interaction (HAI) tests were employed within a flock of sheep maintained in the Sierra-Nevada foothills to assess intra-individual consistency and inter- relatedness of behavioral responses. Groups of five (four or six when needed) ewes were placed in three HAI tests (restrained Human Contact, unrestrained Human Presence and unrestrained Human Approach) at the time of post-breeding, gestation and weaning (3 x per year; over 2 years). PCs were created using principal component analysis (PCA) of behaviors from the unrestrained Human Presence test and were compared to the behaviors from the two other HAI tests to evaluate cross-contextual relationships. Frequency of ‘environmental vigilance’ (EV), ‘investigating fence’ (IF) and duration of ‘head down’ (HD) were the only variables to achieve a moderate repeatability estimate [EV: 0.32 ± 0.09, [CI (0.21, 0.48])]; IF: 0.29 ± 0.13, [CI (0.14, 0.48)]; HD: 0.44 ± 0.15, [CI (0.22, 0.68)]. PCA revealed a single component in all Human Presence tests that was characterized by loadings (>0.45) for duration of ‘grazing’ and ‘environmental vigilance’. Spearman’s rank order analysis revealed no significant correlations between PC1 of each replicate. There was also no significant inter-relatedness identified between behaviors of each HAI test. Taken together, it is suggested that the rangeland ewes of this study exhibited consistency of some individual behaviors within the Human Contact and Human Presence test, however, did not demonstrate a temporally stable trait that can be generalized across multiple contexts. Future work should evaluate the influence of extensive versus intensive management styles on the development and maintenance of human-oriented behavioral traits.

Weak reproductive isolation and extensive gene flow between Mimulus glaucescens and M. guttatus in northern California.

Barriers to reproduction are often how progress in speciation is measured. Nonetheless, an unresolved question concerns the extent to which reproductive barriers diminish gene flow between incipient species. The Sierra Nevada foothill endemic Mimulus glaucescens and the widespread M. guttatus are considered distinct species based on striking differences in vegetative morphology, but barriers to reproduction have not been previously identified, nor has gene flow between species been characterized. Here, we examined 15 potential reproductive barriers within a Northern California area of broad sympatry. Most barriers, with the exception of ecogeographic isolation, were weak or absent, and total isolation for each species was incomplete. Population genomic analyses of range-wide and broadly sympatric accessions revealed extensive gene flow between these taxa, particularly in sympatry. Despite widespread introgression, Mimulus glaucescens, emerged as monophyletic and largely comprised a single ancestry that was found at intermediate frequency within M. guttatus. This result, along with observed ecological and phenotypic differentiation, suggests that natural selection may contribute to the maintenance of distinct phenotypic forms in the earliest stages of speciation. Integrating estimates of barrier strength with direct estimates of gene flow can strengthen a more nuanced interpretation of the process of speciation in natural communities.

Foraging Habitat and Its Effects on the Tricolored Blackbird’s Breeding Distribution and Abundance in the Sierra Nevada Foothills, California

The grassland-dominated eastern Central Valley and Sierra Nevada foothills of California, from Placer to Stanislaus counties, supported at least 43,000–55,000 breeding Tricolored Blackbirds (Agelaius tricolor) annually from 2014 to 2018—about 30% of the statewide population. We found that within 5 km of a colony, the extent of land cover used for foraging, grassland–herbaceous, and to a lesser extent annual crops and irrigated pasture, exceeded their proportions in this region as a whole, suggesting that nesting Tricolored Blackbirds select colony sites where these habitats are more abundant. Other land-cover types were underutilized for foraging, suggesting avoidance. The probability of Tricolored Blackbird occupancy of blocks of 100 km2 was strongly associated with the extent of the selected land-cover types. The relationship between average density of the breeding population and the extent of the selected land-cover types was significant but weaker, implying that other factors are important in determining density. From 2014 to 2018, development and mining eliminated or degraded 9 of 79 colony sites and made 4 others unsuitable by reducing the extent of nearby foraging habitat, although the total breeding population in the region did not decline. We recommend that conservation measures for the Tricolored Blackbird in federally and state-approved habitat-conservation plans in Placer and Sacramento counties, which support the largest breeding populations in the central Sierra foothills but where urban development is rapid, be reevaluated on the basis of recent colony locations and recognition of the critical role of grassland, annual crops, and irrigated pasture as foraging habitat.

Climatic influences on survival and reproductive transitions of big-eared woodrats in California oak woodland

AbstractIt is known that climatic factors can influence the reproductive performance of small mammal populations. However, this information has not been available for the big-eared woodrat (Neotoma macrotis), a keystone species that inhabits the California central coast ranges south to Mexico and the oak woodlands (Quercus spp.) of the western Sierra Nevada foothills. From 2002 to 2014, we livetrapped woodrats on 1.1-ha study plots in coastal-central California and recorded their age and reproductive status. We analyzed these data by a capture-mark-recapture (CMR) framework to estimate state-specific recapture probability (p) and monthly apparent survival (S) of juvenile, non-reproductive, and reproductive adult female woodrats, and the influence of rain and temperature on S and transition probability (Ψ) of the three states. Rainfall from the previous season did not markedly affect survival rates of the states, with one exception: it decreased the survival of nonreproductive woodrats. Nearly all breeding occurred during the cool, wet winter season. Juvenile woodrats had at least a 0.55 probability of breeding by their first winter, conditional on survival. Temperature during the breeding season had a marked negative influence on transition probability. During winter, survival of nonreproductive adult females was significantly higher than for juvenile and reproductive females, indicating a cost of reproduction. Physiological effects and diminished diet quality due to further climate warming could reduce the reproductive success of female big-eared woodrats with negative consequences on population growth and persistence.

What Makes Wildfires Destructive in California?

As human impacts from wildfires mount, there is a pressing need to understand why structures are lost in destructive fires. Despite growing research on factors contributing to structure loss, fewer studies have focused on why some fires are destructive and others are not. We characterized overall differences between fires that resulted in structure loss (“destructive fires”) and those that did not (“non-destructive wildfires”) across three California regions. Then, we performed statistical analyses on large fires only (≥100 ha) to distinguish the primary differences between large destructive large fires and large non-destructive fires. Overall, destructive fires were at least an order of magnitude larger than non-destructive fires, with the largest area burned varying by season in different regions. Fire severity was also significantly higher in destructive than non-destructive fires. The statistical analysis showed that, in the San Francisco Bay Area and the northern Sierra Nevada foothills, proximity to the Wildland Urban Interface (WUI) was by far the most important factor differentiating destructive and non-destructive wildfires, followed by different combinations of short-term weather, seasonal climate, topography, and vegetation productivity. In Southern California, wind velocity on the day of the fire ignition was the top factor, which is consistent with previous assumptions that wind-driven fires tend to be most destructive and most of the destruction occurs within the first 24 h. Additionally, Southern California’s high population density increases the odds that a human-caused wildfire may occur during a severe fire-weather event. The geographical differences among regions and the variation of factors explaining the differences between large destructive and large non-destructive fires reflects the complexity inherent in decision-making for reducing wildfire risk. Land use planning to reduce future exposure of housing development to fire and increased focus on wildfire ignition prevention emerge as two approaches with substantial potential.

A numerical coupled atmospheric–hydrologic modeling system for probable maximum flood estimation with application to California's southern Sierra Nevada foothills watersheds

AbstractEstimation of probable maximum flood (PMF) is a crucial process in water resources management and in the design of large hydraulic structures. However, there are uncertainties in the estimation of hydrologic conditions that contribute to extreme floods. In particular, this is the case in snow‐dominated regions, as surface air temperature and wind speed are understood to have a substantial effect on the magnitude of a flood during a storm event. Motivated by the development of a new approach to investigate and estimate reliable PMF values and in an attempt to resolve the uncertainty issues, this study introduces a physically based modeling approach. For the case study, seven watersheds located in the Sierra‐Nevada mountain range of California, including Cosumnes, Mokelumne, Stanislaus, Tuolumne, Merced, Upper San Joaquin, and Upper Kings were selected. The hydroclimate model was first implemented over the physical boundaries of the study region, and then utilized to simulate possible maximum flood conditions with input from 10 extreme precipitation scenarios. The study results provide evidence of a nonlinear atmospheric–hydrologic system; the extreme 72‐h basin‐averaged precipitation depth was found not to be linearly proportional to 72‐h flow volume equivalent depth. It can also be concluded that a large precipitation depth may not be the sole reason for a large flood event. Temperature and other atmospheric variables also contribute significantly to the production of snowfall and liquid water available for runoff, and to the resulting hydrologic response, such as the flood peak discharge and volume.

Late Jurassic-Early Cretaceous orogenic gold mineralization in the Klamath Mountains, California: Constraints from 40Ar/39Ar dating of hydrothermal muscovite

The Klamath Mountains gold province is the second most important historical producer in California, having produced more than 7 Moz of gold from both lode and placer sources. Hydrothermal muscovite grains from gold-bearing veins provide the first 40Ar/39Ar age constraints indicative of a protracted period of mineralization in the Klamath Mountains. The data indicate that the window for orogenic gold mineralization in the Klamath Mountains was from ~ 160–140 Ma, coinciding in age with the oldest orogenic gold deposits in the Sierra Nevada foothills province to the south, although mineralization continued in the latter along the Mother Lode belt for another 20–30 million years. Despite the broad age overlap between hydrothermal activity and magmatism, the former relates to a regional thermal event, and there is no genetic link between the two. Instead, a correlation exists between the timing of lode gold formation and discrete tectonic events, changes in stress regime, and fault movement. The maximum age corresponds to a major plate reorganization in the Pacific basin and initial gold mineralization continuing into the Sierra Nevada foothills gold province to the south. The minimum age corresponds to the westerly lateral offset of the Klamath Mountains from the Sierra Nevada and the then-active arc, marking the termination of both magmatism and gold-producing hydrothermal activity in the Klamath Mountains. Lode gold mineralization in the Klamath Mountains is compatible with a crustal source of metals and fluids that were released during metamorphic devolatilization and focused via hydrothermal fluid flow along regional faults.

Wyethia Helenoides

Wyethia helenoides is a short, low growing golden-rayed wildflower, that resemble sunflowers. Wyethia helenoides is a species of flowering plants in the sunflower family commonly referred to as gray mule's ears or whitehead mule-ears. Typical understory associates in sunny clearings of mixed oak forests in coastal California. This species occurs chiefly in the California Coast Ranges, Transverse Ranges, Peninsular Ranges, and some areas of the Sierra Nevada foothills in California. The present review attempts to encompass the available literature on Wyethia helenoides with respect to its description, Scientific classification, summary of its various homoeopathic uses.

Design Criteria for Process-Based Restoration of Fluvial Systems

Abstract Process-based restoration of fluvial systems removes human constraints on nature to promote ecological recovery. By freeing natural processes, a resilient ecosystem may be restored with minimal corrective intervention. However, there is a lack of meaningful design criteria to allow designers to evaluate whether a project is likely to achieve process-based restoration objectives. We describe four design criteria to evaluate a project's potential: the expansion of fluvial process space and connectivity lost because of human alterations, the use of intrinsic natural energy to do the work of restoration, the use of native materials that do not overstabilize project elements, and the explicit incorporation of time and adaptive management into project design to place sites on recovery trajectories as opposed to attempts to “restore” sites via a single intervention. Applications include stream and infrastructure design and low-carbon construction. An example is presented in California's Sierra Nevada foothills.

A Comparison of Questing Substrates and Environmental Factors That Influence Nymphal Ixodes pacificus (Acari: Ixodidae) Abundance and Seasonality in the Sierra Nevada Foothills of California.

In California, the western blacklegged tick, Ixodes pacificus Cooley and Kohls, is the principal vector of the Borrelia burgdorferi sensu lato (sl) complex (Spirochaetales: Spirochaetaceae, Johnson et al.), which includes the causative agent of Lyme disease (B. burgdorferi sensu stricto). Ixodes pacificus nymphs were sampled from 2015 to 2017 at one Sierra Nevada foothill site to evaluate our efficiency in collecting this life stage, characterize nymphal seasonality, and identify environmental factors affecting their abundance and infection with B. burgdorferi sl. To assess sampling success, we compared the density and prevalence of I. pacificus nymphs flagged from four questing substrates (logs, rocks, tree trunks, leaf litter). Habitat characteristics (e.g., canopy cover, tree species) were recorded for each sample, and temperature and relative humidity were measured hourly at one location. Generalized linear mixed models were used to assess environmental factors associated with I. pacificus abundance and B. burgdorferi sl infection. In total, 2,033 substrates were sampled, resulting in the collection of 742 I. pacificus nymphs. Seasonal abundance of nymphs was bimodal with peak activity occurring from late March through April and a secondary peak in June. Substrate type, collection year, month, and canopy cover were all significant predictors of nymphal density and prevalence. Logs, rocks, and tree trunks had significantly greater nymphal densities and prevalences than leaf litter. Cumulative annual vapor pressure deficit was the only significant climatic predictor of overall nymphal I. pacificus density and prevalence. No associations were observed between the presence of B. burgdorferi sl in nymphs and environmental variables.

Atlas for a Destroyed World: Frank Day's Painting as Work of Nonvital Revitalization

Atlas for a Destroyed World:Frank Day's Painting as Work of Nonvital Revitalization Mark Minch-de Leon (bio) Once in a while I take up color and paint a little bit, because, if I do not do this, all things will be forgotten. It's good enough all right to sing and talk and explain things on these broadcasts here or especially on tape recording or in records, but it's also nice to have someone who's able to print this or illustrate by color upon a chart. And then it would remain that way. You cannot change it then. And then you've got to be honest and true about it, and not copying from anybody else. But just translating the language, the Maidu language, and putting it up on a chart. And this shows exactly how the Maidu people had been doing before the coming of the white man. —frank day, self-recording, 1975 All the things that I have illustrated here by drawings, paintings, is true because I went to see it. I'm able to take you back to it. —frank day, interview, 1963 All Things Will Be Forgotten Outside of California Indian communities and art and academic circles, Frank Day is largely unknown. His obscurity is compounded by the still mostly unacknowledged catastrophic conditions of his people, the Kóyo•mkàwi Maidu.1 Born in 1902 in the Northern California Sierra Nevada foothills, by Day's own account, he saw the end of a way of life, the end of a world. His grandparents' generation had experienced massacres, abductions, sexual violence, enslavement, removals, and confinement. Day himself was taken as a child and placed in a federal boarding school for forced assimilation. An overdetermined silence on the destruction was created by few survivors, laws barring Indian testimony, settler-centric media, interdictions on speaking of the dead, suppression of languages, abduction of children, and legal prohibitions against ceremonies and gatherings, including for mourning. The continuing pressures of land loss, extreme poverty, lack of political representation, enforced western culture and epistemology, and racism compounded these initial conditions, foreclosing the Maidu relationship to [End Page 56] death in an ongoing catastrophe. Dying in 1976 in the midst of such disaster, Day spent the last sixteen or so years of his life documenting the Maidu world in paint and on recording tape so that things would not be forgotten. The above epigraphs make clear that Day's project of anamnesis is a matter of Indigenous informatics and cartography. Day used paint and tape, images and words to code information and map the (destruction of the) Maidu world in order to transmit information across space and time. The politics of information in this context is fraught, thanks in part to the early twentieth-century anthropological project of salvage ethnography and the critiques it has provoked. In salvage ethnography, much has been written on the separation between those who had direct experience with "traditional" ways of life and those with mere memories. Much scholarship also exists that reframes and sometimes reclaims the work of so-called informants outside such a notion of salvage. This is especially true of Day's generation, who were represented as a bridge between those who lived more traditional lifestyles and the postassimilation generations. These ancestors have, of course, left us an amazing gift in the information they provided, risking the dangers of colonial knowledge-making enterprises to sow the seeds for revitalization projects. The claims of our ancestors to provide access to their worlds are not often taken at face value, with a critical ethics intervening to oppose evaluations of authenticity.2 Focusing on authenticity and its critique, however, risks overemphasizing problematics set out by fields of study such as anthropology and art history, predetermining how we hear the words and see the images of our ancestors and leaving us circling around these knowledge formations in a critical posture, fascinated and revulsed. On the other hand, hearing and seeing our ancestors' mediations too literally, with an ear and eye for realism, couch their often subtle strategies and our Indigenous modes of being in a western metaphysical formalism that consolidates an Indigenous subject and...

Phylogeographic Origin of California Slender Salamanders (Batrachoseps attenuatus) in the Sutter Buttes

The phylogeny of California Slender Salamanders (Batrachoseps attenuatus), which inhabits Northern California's Coast Ranges and Sierra Nevada foothills, was previously investigated by Martínez-Solano et al. (2007), who recovered a monophyletic species that contained five geographically cohesive major clades. However, a population isolate of B. attenuatus found in the Sutter Buttes, a geographically isolated volcanic mountain range within the Sacramento Valley, was not available in their phylogenetic analysis. We sequenced the ∼780-base pair segment of the mitochondrial DNA cytochrome b (cytb) gene used in Martínez-Solano et al. (2007) to examine the phylogenetic placement of this isolated population within the B. attenuatus complex. Our results, based on a single mitochondrial marker, indicate that the Sutter Buttes population of B. attenuatus is genetically distinct and falls within the Martínez-Solano et al. (2007) “East Bay/Sierra subclade” that, in turn, is nested within their “Eastern” major clade. Although we cannot accurately estimate how long the Sutter Buttes population has been isolated, B. attenuatus was likely able to colonize the Sutter Buttes during pluvial Pleistocene interglacials when more contiguous woodlands may have opened dispersal corridors across the Great Central Valley.

Serrated Triangular Arrow Points from Mission Santa Clara: Evidence of Colonial-Period Innovation and Regional Connections

ABSTRACT This article considers a particular form of small, intricately serrated arrow points from central California. Several examples of this point were recovered during recent archaeological mitigation work at Mission Santa Clara de Asís (CA-SCL-30/H), where researchers have referred to them as Mission Santa Clara Serrated (MSCLS) points. Subsequent research indicates that similar points were recovered decades earlier from sites in the Central Valley and Sierra Nevada foothills, but until now had not been formally considered within existing projectile point typologies or regional culture history. We review the known examples of these points, including their physical attributes, geographic distribution, temporal placement, and similarities to previously described serrate Desert Side-Notched points. Our analysis suggests that the MSCLS point style was developed during the colonial period and spread throughout the region via Native Californians’ participation in and rejection of the Franciscan mission system.

Paragenesis of an Orogenic Gold Deposit: New Insights on Mineralizing Processes at the Grass Valley District, California

Abstract The Grass Valley orogenic gold district in the Sierra Nevada foothills province, central California, is the largest historical gold producer of the North American Cordillera. Gold mineralization is associated with shallowly dipping north-south veins hosted by the 160 Ma Grass Valley granodiorite to the southwest of the Grass Valley fault and steeply dipping east-west veins in accreted oceanic rocks to the northeast of this major fault. Quartz veins from both vein types show well-preserved primary textural relationships. Using a combination of petrographic and microanalytical techniques, the paragenetic sequence of minerals within the veins and the compositions of ore minerals were determined to constrain the mechanisms of quartz vein formation and gold deposition. The veins are composed of early quartz that formed through cooling of hydrothermal fluids derived from a geopressured reservoir at depth. The early quartz shows growth zoning in optical cathodoluminescence and contains abundant growth bands of primary inclusions. The primary inclusion assemblages and myriads of crosscutting secondary fluid inclusions have been affected by postentrapment modification, suggesting that early quartz formation was postdated by pronounced pressure fluctuations. These pressure fluctuations, presumably involving changes from lithostatic to hydrostatic conditions, may be related to fault failure of the host structure as predicted by the fault-valve model. Fluid flow associated with pressure cycling took place along microfractures and grain boundaries resulting in extensive recrystallization of the early quartz. Deposition of pyrite, arsenopyrite, and first-generation gold from these hydrothermal fluids causing recrystallization of the early quartz occurred as a result of wall-rock sulfidation. The gold forms invisible gold in the compositionally zoned pyrite or micron-sized inclusions within pyrite growth zones. The latest growth zones in euhedral quartz crystals that formed in association with this stage of the paragenesis contain very rare primary fluid inclusions that have not been affected by postentrapment modification. The hydrothermal system transitioned entirely to hydrostatic conditions immediately after formation of the latest quartz, explaining the preservation of the primary fluid inclusions. The formation of minor quartz in open spaces was followed by the deposition of second-generation native gold and telluride minerals that are commonly associated with base metal sulfides. Ore formation at this stage of the paragenesis is attributed to the rapid decompression of hydrothermal fluids escaping from the geopressured part of the crust into the overlying hydrostatic realm. There is no fluid inclusion evidence that this pressure drop resulted in fluid immiscibility of the hydrothermal fluids. Fluid inclusion evidence suggests that the north-south veins formed at a paleodepth of ~8 km, whereas the east-west veins appear to have formed at ~10 to 11 km below surface, confirming previous inferences that the NE-dipping Grass Valley reverse fault accommodated a large displacement. The findings of the study at Grass Valley have significant implications for the model for orogenic gold deposits, as the reconstruction of the paragenetic relationships provides evidence for the occurrence of two discrete events of gold introduction that occurred at different conditions during the evolution of the hydrothermal system.

Reconstruction of the original extent of the Tertiary pre-volcanic gravels in the northern Sierra Nevada (CA): Implications for the range's Paleotopography

The ancient auriferous gravels that helped spawn the California Gold Rush have figured prominently in investigations of the Cenozoic history of the Sierra Nevada. These fluvial sediments, scattered throughout the northern half of the range, are the remnants of much larger deposits that accumulated throughout the Eocene and Early Oligocene. In this study, we present a reconstruction of the original extent of the gravels developed according to a few simple rules. This reconstruction suggests that large swaths of the northern Sierra Nevada were once buried under broad alluvial plains, a result consistent with previous work. The reconstruction also supports the hypothesis that the gravels accumulated behind high ridges along the Sierra Nevada foothills, with the Yuba River providing an important outlet. Moreover, gravel deposits on two high peaks indicate that the gravels may have buried the Feather River watershed up to the modern crest of the range. Finally, on the basis of our reconstruction, we estimate that the total volume of the gravels was, at a minimum, ∼200 km3.

CONSERVATION GENOMICS OF WYETHIA RETICULATA (ASTERACEAE)

Wyethia reticulata Greene is a rare perennial herb found only on gabbro-derived soils of the Pine Hill formation in the Sierra Nevada foothills of El Dorado County, CA. Wyethia reticulata is capable of both vegetative (clonal) and sexual reproduction, although the former is thought to be more common than the latter, with sexual reproduction tied to fire. The potential dominance of vegetative reproduction has conservation implications for W. reticulata, as populations could appear healthy in terms of stand density, while losing genetic diversity due to a lack of sexual recruitment. Past genetic assessments of W. reticulata relied on low-resolution markers from a small number of populations and did not directly address conservation issues. Here, double-digest random amplified DNA (ddRAD) sequencing was used to develop a high-resolution genomic dataset for a sample of 168 W. reticulata samples from seven locations that represent every known population center of the species. The data was used to 1) calculate the frequency of asexual reproduction, 2) determine which populations contain unique genetic variation, and 3) test whether there are any ecological correlates of genetic patterns. In contrast to past genetic research, the results presented here indicate that clonality is not common; less than 2% of plants were identified as being derived from asexual reproduction. Nevertheless, some locations seem to be more affected by asexuality than others; the index of association varied from 4.4 to 19.4 (M̄ = 10.9). Genetic differentiation among locations was low (Fst = 0.03-0.04). However, clustering identified three distinct population segments that were not previously recognized. Elevation was the only environmental variable significantly associated with genetic differentiation. Based on these results, it is recommended that conservation effort be focused on genetically isolated population segments.

Linking Mesoscale Meteorology With Extreme Landscape Response: Effects of Narrow Cold Frontal Rainbands (NCFR)

AbstractLandscapes evolve in response to prolonged and/or intense precipitation resulting from atmospheric processes at various spatial and temporal scales. Whereas synoptic (large‐scale) features (e.g., atmospheric rivers and hurricanes) govern regional‐scale hydrologic hazards such as widespread flooding, mesoscale features such as thunderstorms or squall lines are more likely to trigger localized geomorphic hazards such as landslides. Thus, to better understand relations between hydrometeorological drivers and landscape response, a knowledge of mesoscale meteorology and its impacts is needed. Here we investigate the extreme geomorphic response associated with one type of mesoscale meteorological feature, the narrow cold frontal rainband (NCFR). Resulting from low‐level convergence and shallow convection along a cold front, NCFRs are narrow bands of high‐intensity rainfall that occur in midlatitude areas of the world. Our study examines an NCFR impacting the Sierra Nevada foothills (California, USA) that initiated over 500 landslides, mobilized ~360,000 metric tons of sediment to the fluvial system (as much as 16 times the local annual sediment yield), and severely damaged local infrastructure and regional water transport facilities. Coupling geomorphological field investigations with meteorological analyses, we demonstrate that precipitation associated with the NCFR was both intense (maximum 15 min intensity of 70 mm/hr) and localized, resulting in a highly concentrated band of shallow landsliding. This meteorological phenomenon likely plays an important role in landscape evolution and hazard initiation. Other types of mesoscale meteorological features also occur globally and offer new avenues for understanding the effects of storms on landscapes.

An Exhumation Pulse From the Nascent Franciscan Subduction Zone (California, USA)

AbstractWe investigated a suite of metabasite blocks from serpentinite matrix and shale matrix mélanges of the California Coast Ranges. Our new data set consists of 40Ar/39Ar dates of amphibole and phengite and U‐Pb dates of metamorphic zircon. Combined with published geochronology, including prograde Lu‐Hf garnet ages from the same blocks, we can reconstruct the timing and time scales of prograde and retrograde metamorphism of individual blocks. In particular we find that exhumation from amphibole‐eclogite facies conditions occurred as a single episode at 165–157 Ma, with an apparent southward younging trend. The rate and timing of exhumation were initially uniform (when comparing individual blocks) and fast (with cooling rates up to ~140°C/Ma). In the cooler and shallower blueschist facies, exhumation slowed and became less uniform among blocks. Considering the subduction zone system, the high‐grade exhumation temporally correlates with a magmatic arc pulse (Sierra Nevada) and the termination of forearc spreading (Coast Range Ophiolite). Our findings suggest that a geodynamic one‐time event led to exhumation of amphibole‐eclogite facies rocks. We propose that interaction of the Franciscan subduction zone with a spreading ridge led to extraction of the forearc mantle wedge from its position between forearc crust and subducting crust. The extraction led to fast and uniform exhumation of subducted rocks into the blueschist facies. We also show that the Franciscan subduction zone did not undergo significant cooling over time and that its initiation was not coeval with blueschist‐facies metamorphism of the Red Ant schist of the Sierra Nevada foothills.

Scalable mapping and monitoring of Mediterranean-climate oak landscapes with temporal mixture models

Mediterranean-climate oak woodlands are prized for their biodiversity, aesthetics, and ecosystem services. Conservation and maintenance of these landscapes requires accurate observations of both present and historic conditions capable of spanning millions of hectares. Decameter optical satellite image time series have the observational coverage to meet this need, with almost 40 years of intercalibrated global observations from the Landsat program alone. However, the optimal approach to leverage these observations for oak ecosystem monitoring remains elusive. Temporal mixture models (TMMs) may offer a solution. TMMs use a linear inverse model based on temporal endmembers (tEMs) chosen to optimize both parsimony and information content by 1) possessing clear biophysical meaning, and 2) accurately representing the variance structure of the observations in the temporal feature space (TFS) composed of low-order Principal Components. We apply this approach to oak woodlands of the California Sierra Nevada foothills. Low-order TFS structure across the ≈1200 km2 study area is consistently bounded by 4 tEM phenologies: annual grasses, evergreen perennials, deciduous perennials + shadow, and unvegetated areas. Satellite-based tEM phenologies correspond to ground-based PhenoCam time series (correlations 0.8 to 0.9). Systematic temporal decimation is conducted to simulate years with varying numbers of cloud free measurements. Fractional cover of temporal endmembers is observed to scale linearly using as few as 6 images per year and coarse feature space topology is retained with as few as 4 well-timed images per year. In comparing 10 m versus 30 m pixel resolution, linear scaling is observed with correlations of 0.78–0.95. Comparison of 10 m Sentinel-2 and LiDAR-derived tree cover estimates at San Joaquin Experimental Range shows a correlation of 0.74. Visual orthophoto validation shows accuracies of annual, deciduous, and evergreen cover fractions of 74–88% (n = 102). Multi-year analysis of August imagery at Sequoia National Park to investigate dynamics associated with the 2012–2016 drought reveals 5 tEMs corresponding to: steady growth, steady decline, early decline then regrowth, persistent vegetation, and no vegetation. Validation images are sparse, but where available show accuracies in the 88 to 91% range for decrease, growth, and persistently vegetated multiyear endmembers (n = 102). Decreases are observed in areas with oak mortality documented in a recent field-based study. Overall, our results suggest the TMM approach has promise as an accurate, explainable, and linearly scalable method for retrospective analysis and prospective monitoring of Mediterranean-climate oak landscapes.