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USGS2011

Mechanical analysis of fault slip data: Implications for paleostress analysis

Stress inversions are a useful and popular tool for structural geologist and seismologist alike. These methods were first introduced by Wallace (1951) and Bott (1959) and subsequent studies continue to be based on their assumptions: the remote stress tensor is spatially uniform for the rock mass containing the faults and temporally constant over the history of faulting in that region, and the slip on each fault surface has the same direction and sense as the maximum shear stress resolved on that surface from the remote stress tensor. Furthermore, successful implementation requires that slip accumulates on faults of diverse orientation. Many studies employ these methods on isolated faults or on fault systems with limited ranges of orientations, which can lead to erroneous results. We propose a new method that incorporates the effects of mechanical interaction of the entire fault or fault system, and solves the complete mechanical problem rather than employing empirical relationships between slip and stress or strain (or strain rate). The method requires knowledge of the fault geometry and information on at least one slip vector component along portions of the known fault geometry. For example, if throw is known, the strike-slip component can be solved for. We test the method using a single synthetic fault with anisotropic roughness similar to that measured at fault outcrops. While the orientation of remote stress may be determined precisely, the lack of diverse fault orientations introduces a systematic error in the remote stress ratio. We further test the effect of diversity of fault orientations and find that Wallace–Bott type inversions do not perform as well for limited ranges of orientations when compared to the proposed method. Finally, we use published data from the 1999 Chi-Chi, Taiwan, earthquake, and find that the method using surface data only, and surface data with subsurface focal mechanisms, produce similar results. The resulting stress orientations are in good agreement with results from Wallace–Bott inversions. Furthermore, the slip distribution is in general agreement with kinematic slip inversions using coseismic surface deformation. Stress inversion methods using fault slip data can thus be improved upon, significantly in some cases, by solving a mechanical boundary value problem that takes into account the geometry of faults or fault systems. As a bonus, the solution provides the stress, strain, and displacement fields throughout the region and the slip distributions on the faults.

Journal of Structural Geology↗

USGS2022

The distribution of clay minerals and their impact on diagenesis in Glen Torridon, Gale crater, Mars

Glen Torridon (GT) is a recessive-trough feature on the northwestern slope of “Mt. Sharp” in Gale crater, Mars with the highest Fe-/Mg-phyllosilicates abundances detected by the Curiosity rover to date. Understanding the origin of these clay minerals and their relationship with diagenetic processes is critical for reconstructing the nature and habitability of past surface and subsurface environments in Gale crater. We aim to constrain the distribution and extent of diagenesis using compositional and morphological trends observed by visible-to-near infrared reflectance spectra in GT from Mastcam and ChemCam, supported by high-resolution images from the Mars Hand Lens Imager. Spectral features consistent with nontronite and fine-grained red hematite are ubiquitous throughout lower GT, and are strongest where diagenetic features are limited, suggesting that both were formed early, before burial. Diagenetic features increase in both abundance and diversity farther up-section, and we observe morphologic evidence for multiple episodes of diagenesis, with the edge of a diagenetic front partially preserved in the middle stratigraphic member, Knockfarril Hill. Near the contact between GT and the overlying Greenheugh pediment capping unit, we observe a lack of clay minerals with signatures consistent instead with coarse-grained gray hematite, likely formed through late-diagenetic alteration. We hypothesize that the sandstone-dominant Stimson formation acted as a conduit for diagenetic fluid flow into the area and that the clay-rich impermeable GT slowed the flow of those fluids, leading to enhanced alteration surrounding the clay-rich portions of GT, including within the nearby Vera Rubin ridge.

JGR Planets↗

USGS2015

SPARROW modeling of nitrogen sources and transport in rivers and streams of California and adjacent states, U.S.

The SPARROW (SPAtially Referenced Regressions On Watershed attributes) model was used to evaluate the spatial distribution of total nitrogen (TN) sources, loads, watershed yields, and factors affecting transport and decay in the stream network of California and portions of adjacent states for the year 2002. The two major TN sources to local catchments on a mass basis were fertilizers and manure (51.7%) and wastewater discharge (15.9%). Other sources contributed < 12%. Fertilizer use is widespread in the Central Valley region of California, and also important in several other regions because of the diversity of California agriculture. Precipitation, sand content of surficial soils, wetlands, and tile drains were important for TN movement to stream reaches. Median streamflow in the study area is about 0.04 m 3 /s. Aquatic losses of nitrogen were found to be most important in intermittent and small to medium sized streams (0.2-14 m 3 /s), while larger streams showed less loss, and therefore are important for TN transport. Nitrogen loss in reservoirs was found to be insignificant, possibly because most of the larger ones are located upstream of nitrogen sources. The model was used to show loadings, sources, and tributary inputs to several major rivers. The information provided by the SPARROW model is useful for determining both the major sources contributing nitrogen to streams and the specific tributaries that transport the load.

California↗

USGS2015

Improving conservation outcomes with a new paradigm for understanding species’ fundamental and realized adaptive capacity

Worldwide, many species are responding to ongoing climate change with shifts in distribution, abundance, phenology, or behavior. Consequently, natural-resource managers face increasingly urgent conservation questions related to biodiversity loss, expansion of invasive species, and deteriorating ecosystem services. We argue that our ability to address these questions is hampered by the lack of explicit consideration of species’ adaptive capacity (AC). AC is the ability of a species or population to cope with climatic changes and is characterized by three fundamental components: phenotypic plasticity, dispersal ability, and genetic diversity. However, few studies simultaneously address all elements; often, AC is confused with sensitivity or omitted altogether from climate-change vulnerability assessments. Improved understanding, consistent definition, and comprehensive evaluations of AC are needed. Using classic ecological-niche theory as an analogy, we propose a new paradigm that considers fundamental and realized AC: the former reflects aspects inherent to species, whereas the latter denotes how extrinsic factors constrain AC to what is actually expressed or observed. Through this conceptualization, we identify ecological attributes contributing to AC, outline areas of research necessary to advance understanding of AC, and provide examples demonstrating how the inclusion of AC can better inform conservation and natural-resource management.

Conservation Letters↗

USGS2014

Biological soil crusts across disturbance-recovery scenarios: effect of grazing regime on community dynamics

Grazing represents one of the most common disturbances in drylands worldwide, affecting both ecosystem structure and functioning. Despite the efforts to understand the nature and magnitude of grazing effects on ecosystem components and processes, contrasting results continue to arise. This is particularly remarkable for the biological soil crust (BSC) communities (i.e., cyanobacteria, lichens, and bryophytes), which play an important role in soil dynamics. Here we evaluated simultaneously the effect of grazing impact on BSC communities (resistance) and recovery after livestock exclusion (resilience) in a semiarid grassland of Central Mexico. In particular, we examined BSC species distribution, species richness, taxonomical group cover (i.e., cyanobacteria, lichen, bryophyte), and composition along a disturbance gradient with different grazing regimes (low, medium, high impact) and along a recovery gradient with differently aged livestock exclosures (short-, medium-, long-term exclusion). Differences in grazing impact and time of recovery from grazing both resulted in slight changes in species richness; however, there were pronounced shifts in species composition and group cover. We found we could distinguish four highly diverse and dynamic BSC species groups: (1) species with high resistance and resilience to grazing, (2) species with high resistance but low resilience, (3) species with low resistance but high resilience, and (4) species with low resistance and resilience. While disturbance resulted in a novel diversity configuration, which may profoundly affect ecosystem functioning, we observed that 10 years of disturbance removal did not lead to the ecosystem structure found after 27 years of recovery. These findings are an important contribution to our understanding of BCS dynamics from a species and community perspective placed in a land use change context.

Ecological Applications↗

USGS1991

Use of Wetland Habitats by Selected Nongame Water Birds in Maine

We examined the use of 87 palustrine and lacustrine wetlands by nongame water birds in central and eastern Maine using 3,527 h of observation (1,501 visits) made during April-August, 1977-85. Wetlands used by 15 species of water birds were distinguished from those not used, according to 20 habitat features. The species were the common loon (Gavia immer) , pied-billed grebe (Podilymbus podiceps), double-crested cormorant (Phalacrocorax auritus), American bittern (Botaurus lentiginosus), great blue heron (Ardea herodias), green-backed heron (Butorides striatus), osprey (Pandion haliaetus), bald eagle (Haliaeetus leucocephalus), northern harrier (Circus cyaneus), Virgima rail (Rallus limicola), sora (Porzana carolina), spotted sandpiper (Actitis macularia), common snipe (Gallinago gallinago), herring gull (Larus argentatus), and belted kingfisher (Ceryle alcyon). Predictive models of habitat use were developed for each species. Water birds were classified by similarity of habitats used, and species use was contrasted by wetland type. Smaller, isolated wetlands were used by fewer (P < 0.05) species than larger wetlands in complexes; many species had large area-requirements (pied-billed grebe, common loon, herring gull, double-crested cormorant, bald eagle) or preferred to use wetlands near other wetlands (common loon, herring gull, great blue heron, spotted sandpiper, osprey, bald eagle). Wetland area contributed more to overall variation in species richness on wetlands than wetland isolation, although on small wetlands (<3.6 ha) isolation was a better predictor of species richness than wetland area. Wetlands with intermediate amounts (33-66%) of emergent vegetation supported more species (P< 0.05) than closed (>66%) or open (<33%) wetlands. Low pH typified wetlands used by large-bodied piscivores (common loon, cormorant, osprey). Other water birds were associated with more densely vegetated, chemically buffered wetlands. Habitat features associated with wetland use by each waterbird species are reported, as are numerical responses of waterbird populations to wetland features and estimates of annual variation in habitat occupancy. Lacustrine wetlands supported a distinct, low diversity community of water birds, including most fish-eating species. Waterbird diversity at forested palustrine wetlands was intermediate between lacustrine communities and more species-rich assemblages at palustrine emergent and scrub-shrub wetlands. Regional variation in wetland characteristics and water bird use was associated with surficial geology, soils, and management practices. Management for nongame water birds in Maine should consider providing emergent and aquatic-bed vegetation with variable cover-to-water ratios, accommodating species-specific habitat needs, focusing on species of restricted distribution and low abundance, and maintaining wetland complexes. Bird use and habitat information from 87 wetlands and models of habitat selection for each species are provided in appendixes.

Fish and Wildlife Research↗

USGS2022

Simulation experiments comparing nonstationary design-flood adjustments based on observed annual peak flows in the conterminous United States

While nonstationary flood frequency analysis (NSFFA) methods have proliferated, few studies have rigorously compared them for modeling changes in both the central tendency and variability of annual peak-flow series, also known as the annual maximum series (AMS), in hydrologically diverse areas. Through Monte Carlo experiments, we appraise five methods for updating estimates of 10- and 100-year floods at gauged sites using synthetic records based on sample moments and change trajectories of observed AMS in the conterminous United States (CONUS). We compare two methods that consider changes in both central tendency and variability - a Gamma generalized linear model estimated with weighted least squares and the Generalized Additive Model for Location, Scale, Shape (GAMLSS) - with a distribution-free approach (quantile regression), and baseline cases assuming stationarity or only changes in central tendency. ‘Trend-space’ plots identify realistic AMS changes for which modeling trends in both central tendency and variability were warranted based on fractional root mean squared errors (fRMSE). They also reveal statistical properties of AMS under which NSFFA models perform especially well or poorly. For instance, quantile regression performed especially well (poorly) under strong negative (positive) skewness. Although the nonstationary LP3 distribution accommodates most AMS with trends well, the sensitivity of NSFFA model performance to different sample moments and trends suggests the need for more flexibility in prescribing design-flood adjustments in the CONUS. A follow-up comparison of regional NSFFA models pooling at-site AMS would further illuminate NSFFA guidance, especially for AMS with properties less conducive to NSFFA modeling, such as positive skewness and increasing variability.

Journal of Hydrology X↗

USGS2016

Barrier displacement on a neutral landscape: Towards a theory of continental biogeography

Macroevolutionary theory posits three processes leading to lineage diversification and the formation of regional biotas: dispersal (species geographic range expansion), speciation (species lineage splitting), and extinction (species lineage termination). The Theory of Island Biogeography (TIB) predicts species richness values using just two of these processes; dispersal and extinction. Yet most species on Earth live on continents or continental shelves, and the dynamics of evolutionary diversification at regional and continental scales are qualitatively different from those that govern the formation of species richness on biogeographic islands. Certain geomorphological processes operating perennially on continental platforms displace barriers to gene flow and organismal dispersal, and affect all three terms of macroevolutionary diversification. For example, uplift of a dissected landscape and river capture both merge and separate portions of adjacent areas, allowing dispersal and larger geographic ranges, vicariant speciation and smaller geographic ranges, and extinction when range sizes are subdivided below a minimum persistence threshold. The TIB also does not predict many biogeographic and phylogenetic patterns widely observed in continentally distributed taxa, including: 1, power function-like species-area relationships; 2, log-normal distribution of species geographic range sizes, in which most species have restricted ranges (are endemic) and few species have broad ranges (are cosmopolitan); 3, mid-domain effects with more species towards the geographic center, and more early-branching, species-poor clades towards the geographic periphery; 4, exponential rates of net diversification with log-linear accumulation of lineages through geological time; and 5, power function-like relationships between species-richness and clade diversity, in which most clades are species-poor and few clades are species-rich. Current theory does not provide a robust mechanistic framework to connect these seemingly disparate patterns. Here we present SEAMLESS (Spatially-Explicit Area Model of Landscape Evolution by SimulationS) that generates clade diversification by moving geographic barriers on a continuous, neutral landscape. SEAMLESS is a neutral Landscape Evolution Model (LEM) that treats species and barriers as functionally equivalent with respect to model parameters. SEAMLESS differs from other model-based biogeographic methods (e.g. Lagrange, GeoSSE, BayArea, BioGeoBEARS) by modeling properties of dispersal barriers rather than areas, and by modeling the evolution of species lineages on a continuous landscape, rather than the evolution of geographic ranges along branches of a phylogeny. SEAMLESS shows how dispersal is required to maintain species richness and avoid clade-wide extinction, demonstrates that ancestral range size does not predict species richness, and provides a unified explanation for the suite of commonly observed biogeographic and phylogenetic patterns listed above. SEAMLESS explains how a simple barrier-displacement mechanism affects lineage diversification under neutral conditions, and is advanced here towards the formulation of a general theory of continental biogeography.

Systematic Biology↗

USGS2025

Scalable environmental DNA methods reveal strong associations between landscape-scale forest habitat and insect richness

While aquatic environmental DNA (eDNA) methods have reached relative maturity, terrestrial eDNA methods are nascent and have yet to reach widespread use. Field-ready applications require eDNA survey methods where samples are easy to collect by inexperienced practitioners, easy to transport between the field and lab, and easy to process thereafter. Here, we demonstrate methods that satisfy these requirements and show strong potential for characterizing diverse terrestrial eDNA samples collected from flower and leaf surfaces. We used novel methods to collect and process 236 flower eDNA samples and 21 leaf surface eDNA samples, obtaining 2,228 Arthropoda eDNA detections spanning 175 families using amplicon sequencing of two genetic markers. Detected taxa were diverse and included numerous groups of conservation concern, such as bees (Hymenoptera; Anthophila, 32 genera spanning 5 families) and Lepidoptera (209 genera from 21 families). Data reveal strong associations between insect community richness and remotely sensed measures of forest habitat, providing a quantitative perspective of relevance to insect conservation. It is increasingly clear that a variety of organisms readily disperse eDNA throughout the environment, supporting the notion that eDNA will be a powerful tool for characterizing species distributions and monitoring at-risk species. However, we conclude that researchers seeking to characterize fine-scale habitat associations or plant-pollinator interactions using eDNA will need to carefully design studies with appropriate field controls, such as the leaf surface eDNA samples collected here.

BioRxiv↗

USGS2008

Preliminary classification of water areas within the Atchafalaya Basin Floodway System by using landsat imagery

The southern portion of the Atchafalaya Basin Floodway System (ABFS) is a large area (2,571 km 2 ) in south central Louisiana bounded on the east and west sides by a levee system. The ABFS is a sparsely populated area that includes some of the Nation's most significant extents of bottomland hardwoods, swamps, bayous, and backwater lakes, holding a rich abundance and diversity of terrestrial and aquatic species. The seasonal flow of water through the ABFS is critical to maintaining its ecological integrity. Because of strong interdependencies among species, habitat quality, and water flow in the ABFS, there is a need to better define the paths by which water moves at various stages of the hydrocycle. Although river level gages have collected a long historical record of water level variation, very little synoptic information has been available regarding the distribution and character of water at more remote locations in the basin. Most water management plans for the ABFS strive to improve water quality by increasing water flow and circulation from the main stem of the Atchafalaya River into isolated areas. To describe the distribution of land and water on a basin-wide scale, we chose to use Landsat 5 and Landsat 7 imagery to determine the extent of water distribution from 1985 to 2006 and at a variety of river stages. Because the visual signature of river water is high turbidity, we also used Landsat imagery to describe the distribution of turbid water in the ABFS. The ability to track water flow patterns by tracking turbid waters will enhance the characterization of water movement and aid in planning.

Louisiana↗

USGS2015

Porphyry copper assessment of the Central Asian Orogenic Belt and eastern Tethysides: China, Mongolia, Russia, Pakistan, Kazakhstan, Tajikistan, and India: Chapter X in Global mineral resource assessment

The U.S. Geological Survey collaborated with international colleagues to assess undiscovered resources in porphyry copper deposits in the Central Asian Orogenic Belt and eastern Tethysides. These areas host 20 known porphyry copper deposits, including the world class Oyu Tolgoi deposit in Mongolia that was discovered in the late 1990s. The study area covers major parts of the world’s largest orogenic systems. The Central Asian Orogenic Belt is a collage of amalgamated Precambrian through Mesozoic terranes that extends from the Ural Mountains in the west nearly to the Pacific Coast of Asia in the east and records the evolution and final closure of the Paleo-Asian Ocean in Permian time. The eastern Tethysides, the orogenic belt to the south of the Central Asian Orogenic Belt, records the evolution of another ancient ocean system, the Tethys Ocean. The evolution of these orogenic belts involved magmatism associated with a variety of geologic settings appropriate for formation of porphyry copper deposits, including subduction-related island arcs, continental arcs, and collisional and postconvergent settings. The original settings are difficult to trace because the arcs have been complexly deformed and dismembered by younger tectonic events. Twelve mineral resource assessment tracts were delineated to be permissive for the occurrence of porphyry copper deposits based on mapped and inferred subsurface distributions of igneous rocks of specific age ranges and compositions. These include (1) nine Paleozoic tracts in the Central Asian Orogenic Belt, which range in area from about 60,000 to 800,000 square kilometers (km 2 ); (2) a complex area of about 400,000 km 2 on the northern margin of the Tethysides, the Qinling-Dabie tract, which spans central China and areas to the west, encompassing Paleozoic through Triassic igneous rocks that formed in diverse settings; and (3) assemblages of late Paleozoic and Mesozoic rocks that define two other tracts in the Tethysides, the 100,000 km 2 Jinsajiang tract and the 300,000 km 2 Tethyan-Gangdese tract. Assessment participants evaluated applicable grade and tonnage models and estimated numbers of undiscovered deposits at different confidence levels for each permissive tract. The estimates were then combined with the selected grade and tonnage models using Monte Carlo simulations to generate probabilistic estimates of undiscovered resources. Additional resources in extensions of deposits with identified resources were not specifically evaluated. Assessment results, presented in tables and graphs, show amounts of metal and rock in undiscovered deposits at selected quantile levels of probability (0.95, 0.9, 0.5, 0.1, and 0.05 confidence levels), as well as the arithmetic mean and associated standard deviations and variances for each tract. This assessment estimated a total of 97 undiscovered porphyry copper deposits within the assessed permissive tracts. This represents nearly five times the 20 known deposits. Predicted mean resources that could be associated with these undiscovered deposits are about 370,000,000 metric tons (t) of copper, 10,000 t of gold, 7,700,000 t of molybdenum, and 120,000 t of silver. The assessment area is estimated to contain about five times as much copper in undiscovered deposits as has been identified to date. This report includes a summary of the data used in the assessment, a brief overview of the geologic framework of the area, descriptions of permissive tracts and known deposits, maps, and tables. A geographic information system database that accompanies this report includes the tract boundaries and known porphyry copper deposits, significant prospects, and prospects. Assessments of overlapping younger rocks and adjacent areas are included in separate reports available on-line at http://minerals.usgs.gov/global/ .

Scientific Investigations Report↗

USGS2018

Discontinuities and functional resilience of large river fish assemblages

Functional composition of communities across scales is increasingly used to infer resilience of biotic communities to environmental change. To assess the relevance of these concepts to management of large rivers, analyses were applied to fish community data of the Upper Mississippi River. First, to evaluate whether there was evidence for structural patterns in fish size distributions, a discontinuity analysis was performed. Using long‐term fish data, consistent discontinuities were identified across 14 reaches, suggesting similar structuring processes occur throughout the nearly 1300 river kilometers represented by those reaches. Increased variability in species abundance in relation to proximity to edges of body size aggregations supports the discontinuity hypothesis that body size aggregations are structured by key processes. Functional richness and redundancy were quantified within and across identified scales for each of 14 river reaches. Diversity of trophic and spawning guilds was generally greater in the upstream reaches in comparison with downstream reaches, with the exception of the diversity of large‐bodied spawning guilds. Evidence of functional shifts in the composition of fishes occurred, but differed by size aggregations, likely reflecting scale‐specific resource availability. Redundancy of spawning and trophic groups across body size aggregations suggested downstream reaches of this system may be less resilient to disturbances and were weakly associated with reduced habitat diversity. These findings suggest that discontinuities in large river fish assemblages do occur and may provide indication of shifting resource availability. Further investigation of the underlying processes and scales that support resource availability will be critical to managing for resilience in large river ecosystems.

Upper Mississippi River↗

USGS2011

Groupers on the edge: Shelf edge spawning habitat in and around marine reserves of the northeastern Gulf of Mexico

The northeastern Gulf of Mexico contains some of the most diverse and productive marine habitat in the United States. Much of this habitat, located on the shelf edge in depths of 50 to 120 m, supports spawning for many economically important species, including groupers. Here, we couple acoustic surveys with georeferenced videography to describe the primary spatial and geologic features of spawning aggregation sites for four economically important species: gag ( Mycteroperca microlepis ), scamp ( M. phenax ), red grouper ( Epinephelus morio ), and red snapper ( Lutjanus campechanus ), with notes on fish distribution and abundance and spawning activities. We provide information on movement patterns of reef fish determined using acoustic telemetry. Finally, we discuss the possible coupling of geomorphology with hydrographic features to influence the overall productivity of the region and the importance of spatial fishery management in sustaining that productivity.

Northeastern Gulf of Mexico↗

USGS2015

Effects of topoclimatic complexity on the composition of woody plant communities

Topography can create substantial environmental variation at fine spatial scales. Shaped by slope, aspect, hill-position and elevation, topoclimate heterogeneity may increase ecological diversity, and act as a spatial buffer for vegetation responding to climate change. Strong links have been observed between climate heterogeneity and species diversity at broader scales, but the importance of topoclimate for woody vegetation across small spatial extents merits closer examination. We established woody vegetation monitoring plots in mixed evergreen-deciduous woodlands that spanned topoclimate gradients of a topographically heterogeneous landscape in northern California. We investigated the association between the structure of adult and regenerating size classes of woody vegetation and multidimensional topoclimate at a fine scale. We found a significant effect of topoclimate on both single-species distributions and community composition. Effects of topoclimate were evident in the regenerating size class for all dominant species (four Quercus spp. , Umbellularia californica and Pseudotsuga menziesii ) but only in two dominant species ( Quercus agrifolia and Quercus garryana ) for the adult size class. Adult abundance was correlated with water balance parameters (e.g. climatic water deficit) and recruit abundance was correlated with an interaction between the topoclimate parameters and conspecific adult abundance (likely reflecting local seed dispersal). However, in all cases, the topoclimate signal was weak. The magnitude of environmental variation across our study site may be small relative to the tolerance of long-lived woody species. Dispersal limitations, management practices and patchy disturbance regimes also may interact with topoclimate, weakening its influence on woody vegetation distributions. Our study supports the biological relevance of multidimensional topoclimate for mixed woodland communities, but highlights that this relationship might be mediated by interacting factors at local scales.

California↗

USGS1986

Shuttle imaging radar: Physical controls on signal penetration and subsurface scattenng in the Eastern Sahara

SIR-A signal penetration and subsurface backscatter within the upper meter or so of the sediment blanket in the Eastern Sahara of southern Egypt and northern Sudan are enhanced both by radar sensor parameters and by the physical and chemical characteristics of eolian and alluvial materials. Interpretation of SIR-A images by McCauley et al. [1], [2] dramatically changed previous concepts of the role that fluvial processes have played over the past 10000 to 30000000 years in shaping this now extremely flat, featureless, and hyperarid landscape. In the present paper we summarize the near-surface stratigraphy, the electrical properties of materials, and the types of radar interfaces found to be responsible for different classes of SIR-A tonal response. The dominant factors related to efficient microwave signal penetration into the sediment blanket include a) favorable distribution of particle sizes, b) extremely low moisture content and c) reduced geometric scattering at the SIR-A frequency (1.3 GHz). The depth of signal penetration that results in a recorded backscatter, here called "radar imaging depth," was documented in the field to be a maximum of 1.5 m, or 0.25 of the calculated "skin depth," for the sediment blanket. Radar imaging depth is estimated to be between 2 and 3 m for active sand dune materials. Diverse permittivity interfaces and volume scatterers within the shallow subsurface are responsible for most of the observed backscatter not directly attributable to grazing outcrops.

IEEE Transactions on Geoscience and Remote Sensing↗

USGS2010

Integrating physiology, population dynamics and climate to make multi-scale predictions for the spread of an invasive insect: The Argentine ant at Haleakala National Park, Hawaii

Mechanistic models for predicting species’ distribution patterns present particular advantages and challenges relative to models developed from statistical correlations between distribution and climate. They can be especially useful for predicting the range of invasive species whose distribution has not yet reached equilibrium. Here, we illustrate how a physiological model of development for the invasive Argentine ant can be connected to differences in micro-site suitability, population dynamics and climatic gradients; processes operating at quite different spatial scales. Our study is located in the subalpine shrubland of Haleakala National Park, Hawaii, where the spread of Argentine ants Linepithema humile has been documented for the past twenty-five years. We report four main results. First, at a microsite level, the accumulation of degree-days recorded in potential ant nest sites under bare ground or rocks was significantly greater than under a groundcover of grassy vegetation. Second, annual degree-days measured where population boundaries have not expanded (456-521 degree-days), were just above the developmental requirements identified from earlier laboratory studies (445 degree-days above 15.98C). Third, rates of population expansion showed a strong linear relationship with annual degree-days. Finally, an empirical relationship between soil degree-days and climate variables mapped at a broader scale predicts the potential for future range expansion of Argentine ants at Haleakala, particularly to the west of the lower colony and the east of the upper colony. Variation in the availability of suitable microsites, driven by changes in vegetation cover and ultimately climate, provide a hierarchical understanding of the distribution of Argentine ants close to their cold-wet limit of climatic tolerances. We conclude that the integration of physiology, population dynamics and climate mapping holds much promise for making more robust predictions about the potential spread of invasive species.

Hawaii↗

USGS1983

Water-resources investigations of the U.S. Geological Survey in New Mexico; fiscal year 1981

The Water Resources Division of the U.S. Geological Survey investigates the occurrence, quantity, quality, distribution, and movement of the Nation 's surface and underground waters, and coordinates Federal water data acquisition activities. During fiscal year 1981, the New Mexico District had 40 active projects, released 19 reports, and answered hundreds of requests of water-related information. Investigations included the following: (1) chemical quality of surface water in New Mexico; (2) chemical quality of groundwater in New Mexico; (3) sediment transport in New Mexico streams; (4) surface water supply; (5) surface water diversions for irrigation; (6) streamflow characteristics; (7) effect of urban development on storm runoff; (8) inundation from floods; (9) effects of groundwater pumping; (10) long-term monitoring of groundwater levels; (11) groundwater and surface water relationships; (12) consumptive use by phreatophytes; (13) hydrologic impacts of energy development; and (14) groundwater supplies. (Lantz-PTT)

Open-File Report↗

USGS2023

Potential effects of habitat change on migratory bird movements and avian influenza transmission in the East Asian-Australasian Flyway

Wild waterbirds, and especially wild waterfowl, are considered to be a reservoir for avian influenza viruses, with transmission likely occurring at the agricultural-wildlife interface. In the past few decades, avian influenza has repeatedly emerged in China along the East Asian-Australasian Flyway (EAAF), where extensive habitat conversion has occurred. Rapid environmental changes in the EAAF, especially distributional changes in rice paddy agriculture, have the potential to affect both the movements of wild migratory birds and the likelihood of spillover at the agricultural-wildlife interface. To begin to understand the potential implications such changes may have on waterfowl and disease transmission risk, we created dynamic Brownian Bridge Movement Models (dBBMM) based on waterfowl telemetry data. We used these dBBMM models to create hypothetical scenarios that would predict likely changes in waterfowl distribution relative to recent changes in rice distribution quantified through remote sensing. Our models examined a range of responses in which increased availability of rice paddies would drive increased use by waterfowl and decreased availability would result in decreased use, predicted from empirical data. Results from our scenarios suggested that in southeast China, relatively small decreases in rice agriculture could lead to dramatic loss of stopover habitat, and in northeast China, increases in rice paddies should provide new areas that can be used by waterfowl. Finally, we explored the implications of how such scenarios of changing waterfowl distribution may affect the potential for avian influenza transmission. Our results provide advance understanding of changing disease transmission threats by incorporating real-world data that predicts differences in habitat utilization by migratory birds over time.

Diversity↗