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At least 937 records · Page 52Linked to original sources
USGS2018

A consistent global approach for the morphometric characterization of subaqueous landslides

Landslides are common in aquatic settings worldwide, from lakes and coastal environments to the deep sea. Fast-moving, large-volume landslides can potentially trigger destructive tsunamis. Landslides damage and disrupt global communication links and other critical marine infrastructure. Landslide deposits act as foci for localized, but important, deep-seafloor biological communities. Under burial, landslide deposits play an important role in a successful petroleum system. While the broad importance of understanding subaqueous landslide processes is evident, a number of important scientific questions have yet to receive the needed attention. Collecting quantitative data is a critical step to addressing questions surrounding subaqueous landslides. Quantitative metrics of subaqueous landslides are routinely recorded, but which ones, and how they are defined, depends on the end-user focus. Differences in focus can inhibit communication of knowledge between communities, and complicate comparative analysis. This study outlines an approach specifically for consistent measurement of subaqueous landslide morphometrics to be used in the design of a broader, global open-source, peer-curated database. Examples from different settings illustrate how the approach can be applied, as well as the difficulties encountered when analysing different landslides and data types. Standardizing data collection for subaqueous landslides should result in more accurate geohazard predictions and resource estimation.

Geological Society, London, Special Publications↗
USGS2011

The indication of Martian gully formation processes by slope-area analysis

The formation process of recent gullies on Mars is currently under debate. This study aims to discriminate between the proposed formation processes - pure water flow, debris flow and dry mass wasting - through the application of geomorphological indices commonly used in terrestrial geomorphology. High-resolution digital elevation models (DEMs) of Earth and Mars were used to evaluate the drainage characteristics of small slope sections. Data from Earth were used to validate the hillslope, debris-flow and alluvial process domains previously found for large fluvial catchments on Earth, and these domains were applied to gullied and ungullied slopes on Mars. In accordance with other studies, our results indicate that debris flow is one of the main processes forming the Martian gullies that were being examined. The source of the water is predominantly distributed surface melting, not an underground aquifer. Evidence is also presented indicating that other processes may have shaped Martian crater slopes, such as ice-assisted creep and solifluction, in agreement with the proposed recent Martian glacial and periglacial climate. Our results suggest that, within impact craters, different processes are acting on differently oriented slopes, but further work is needed to investigate the potential link between these observations and changes in Martian climate.

Geological Society Special Publication↗
USGS2002

Threats to desert tortoise populations: a critical review of the literature

Decision in resource management are generally based on a combination of sociopolitical, economic, and environmental factors, and may be biased by personal values. These three components often contradict each other resulting in controversy. Controversies can usually be reduced when solid scientific evidence is used to support or refute a decision. However, it is important to recognize that data often do little to alter antagonists' positions when differences in values are the bases if the dispute. But, supporting data can make the decision more defensible, both legally and ethically, especially if the data supporting all opposing viewpoints are included in the decision-making process. Resource management decisions must be made using the best scientific information currently available. However, scientific data vary in two important measures of quality: reliability and validity. The reliability of the data is a measure of the degree to which the observations or conclusion can be repeated. Validity of the data is a measure of the degree to which the observation or conclusion reflects what actually occurs in nature. How the data are collected strongly affects the reliability of validity of ecological conclusions that can be made. Research data potentially relevant to management come from different sources, and the source often provides clues to the reliability and, to a certain extent, validity of data. Understanding the quality of data being used to make management decisions helps to separate the philosophical or value-based aspects of arguments from the objective ones, thus helping to clarify the decisions and judgments that need to be made. The West Mojave Plan is a multispecies, bioregional plan for the management of natural resources within a 9.4 million-acre area of the Mojave Desert in California. The plan addresses the legal requirements for the recovery of the desert tortoise ( Gopherus agazzizii ), a threatened species, but also covers an additional approximately 80 species of plants and animals assigned special status by the Bureau of Land Management, U. S. Fish and Wildlife Service, and California Department of Fish and Game. Within the planning area, 28 separate jurisdictions (counties, cities, towns, military installations, etc.) seek programmatic prescriptions that will facilitate streamlined environmental review, result in expedited authorization for development projects, and protect listed and unlisted species into the foreseeable future to avoid or minimize conflicts between proposed development and species' conservation and recovery. All of the scientific data available concerning the biology and management of these approximately 80 species and their habitats must be evaluated to develop a scientifically credible plan. This document provides an overview and evaluation of the knowledge of the major threats to the persistence and recovery of desert tortoise populations. I was specifically asked to evaluate the scientific veracity of the data and reports available. I summarize the data presently available with particular focus on the West Mojave Desert, evaluate the scientific integrity of the data. and identify major gaps in the available knowledge. I do not attempt to provide in-depth details on each study or threat; for more details I encourage the reader to consult the individual papers or reports city throughout this report (many of which are available at most university libraries and at the West Mojave Plan office in Riverside, California). I also do not attempt to characterize or evaluate the past or present management actions, except where they have direct bearing on evaluation of threats, nor do I attempt, for the most part, to acquire, generate, or evaluate new or existing, but uninterpreted data.

California↗
USGS2024

Environmental DNA dynamics of three species of unionid freshwater mussels

North American freshwater mussels are of special conservation concern due to their high endemism and the multiple anthropogenic stressors affecting them. Of the over 300 species in North America, nearly one third of these species are federally listed as threatened or endangered. Environmental DNA (eDNA) analysis has been successful in detecting freshwater mussels and could aid in monitoring their populations. Production and degradation rates of eDNA for the species of interest are needed to inform interpretation of eDNA detections, allow possible modeling of relative abundance and population location, and aid in mussel conservation through population identification. Here, we designed and tested qPCR assays for three freshwater mussel species, mucket ( Ortmanniana ligamentina ), fatmucket ( Lampsilis siliquoidea ), and the federally endangered spectaclecase ( Cumberlandia monodonta ). We performed laboratory experiments under controlled conditions to measure eDNA shedding and degradation rates for each species. Different biomasses, temperatures, and food regimens were tested independently to determine if these factors influence the amount of DNA produced by the mussels. Degradation rates of eDNA were measured from experimental tank water after mussels were removed. Overall, we observed low eDNA shedding rates for freshwater mussels compared to previous studies of fish eDNA shedding rates. Furthermore, temperature and feeding showed limited or no significant effects in the species studied. Environmental DNA degradation rates were consistent with those reported in the literature for other taxa. Collectively, our results will be useful for designing eDNA monitoring studies, modeling eDNA dispersal, and interpreting eDNA results to help inform freshwater mussel conservation efforts.

Environmental DNA↗
USGS2017

Exploring potential effects of cormorant predation on the fish community in Saginaw Bay, Lake Huron

Stakeholders and fishery managers expressed concern that double-crested cormorant Phalacrocorax auritus predation may be a factor in the recent poor survival of yellow perch Perca flavescens in Saginaw Bay. We quantified cormorant diets from two nesting colonies in Saginaw Bay during April–September in 2013 and 2014, with special emphasis on impacts to yellow perch. Cormorants ( n = 691) were collected when returning to colonies after foraging. Stomachs were removed and preserved in the field. Diet items were identified, enumerated, and measured ( n = 23.373). Cormorant diets from Saginaw Bay indicate a heavy reliance on round goby and Notropis species as prey during the breeding season, consistent with other areas of the Great Lakes where round goby and cormorants coincide. Respectively, the three most common prey species observed by number (%) and biomass (%) pooled across years and sites were round goby Neogobius melanostomus (56.6%, 42.1%), emerald shiner Notropis antherinoides (25.2%, 12.5%), and yellow perch (8.0%, 14.1%). Diet composition was more variable at Spoils Island than at Little Charity Island. Overall cormorant consumption (estimated using cormorant consumption demand rates) of yellow perch was compared to walleye consumption. Cormorant consumption of age-1 yellow perch was 13–17% as much as mean walleye consumption of yellow perch in 2013 and 8–11% in 2014. The cumulative effects of walleye and spring cormorant predation likely represent a recruitment bottleneck for yellow perch in Saginaw Bay. Future studies determining age-specific abundance of yellow perch would facilitate better determination of cormorant predation significance.

Lake Huron, Saginaw Bay↗
USGS2005

A comparative analysis of the Global Land Cover 2000 and MODIS land cover data sets

Accurate and up-to-date global land cover data sets are necessary for various global change research studies including climate change, biodiversity conservation, ecosystem assessment, and environmental modeling. In recent years, substantial advancement has been achieved in generating such data products. Yet, we are far from producing geospatially consistent high-quality data at an operational level. We compared the recently available Global Land Cover 2000 (GLC-2000) and MODerate resolution Imaging Spectrometer (MODIS) global land cover data to evaluate the similarities and differences in methodologies and results, and to identify areas of spatial agreement and disagreement. These two global land cover data sets were prepared using different data sources, classification systems, and methodologies, but using the same spatial resolution (i.e., 1 km) satellite data. Our analysis shows a general agreement at the class aggregate level except for savannas/shrublands, and wetlands. The disagreement, however, increases when comparing detailed land cover classes. Similarly, percent agreement between the two data sets was found to be highly variable among biomes. The identified areas of spatial agreement and disagreement will be useful for both data producers and users. Data producers may use the areas of spatial agreement for training area selection and pay special attention to areas of disagreement for further improvement in future land cover characterization and mapping. Users can conveniently use the findings in the areas of agreement, whereas users might need to verify the informaiton in the areas of disagreement with the help of secondary information. Learning from past experience and building on the existing infrastructure (e.g., regional networks), further research is necessary to (1) reduce ambiguity in land cover definitions, (2) increase availability of improved spatial, spectral, radiometric, and geometric resolution satellite data, and (3) develop advanced classification algorithms.

Remote Sensing of Environment↗
USGS1993

Chronology of Elk Lake sediments: Coring, sampling, and time-series construction

A 22 m series of cores from a continuously laminated sequence of postglacial sediment was recovered from 29.6 m of water from the deepest part of Elk Lake, Clearwater County, Minnesota, by piston and freeze-coring methods during the winters of 1978 and 1982. A varve time series constructed and used as a basis for subsampling the cores and samples, based on the varve chronology, allows precise determination of fluxes of geochemical and biological sediment components. Chronological and petrographic studies have shown that the laminations are varves and their measurement and enumeration has produced a 10,400 year time series that estimates the rates and timing of paleolimnologic and paleoenvironmental changes in Elk Lake and its drainage. A radiocarbon date from surface sediment is 850 years. The difference between radiocarbon and varve dates continues down core; varve dates are older than radiocarbon dates, probably because of systematic incorporation of dead carbon (as bicarbonate) in organic matter in the sediment. Varve-dated boundaries of pollen zones in the Elk Lake cores compare closely with the ages of the same zones in cores from nearby lakes that have been radiocarbon dated.

Minnestoa↗
USGS2011

Evidence for foraging -site fidelity and individual foraging behavior of pelagic cormorants rearing chicks in the Gulf of Alaska

The Pelagic Cormorant ( Phalacrocorax pelagicus ) is the most widespread cormorant in the North Pacific, but little is known about its foraging and diving behavior. However, knowledge of seabirds' foraging behavior is important to understanding their function in the marine environment. In 2006, using GPS dataloggers, we studied the foraging behavior of 14 male Pelagic Cormorants rearing chicks on Middleton Island, Alaska. For foraging, the birds had high fidelity to a small area 8 km north of the colony. Within that area, the cormorants' diving activity was of two distinct kinds—near-surface dives (1–6 m) and benthic dives (28–33 m). Individuals were consistent in the depths of their dives, either mostly shallow or mostly deep. Few showed no depth preference. Dive duration, time at maximum depth, and pauses at the water surface between consecutive dives were shorter for shallow dives than for deep dives. The cormorants made dives of both types throughout the day, but the frequency of deep dives increased toward evening. Maximum foraging range was 9 km; maximum total distance traveled per trip was 43.4 km. Trip durations ranged from 0.3 to 7.7 hr. Maximum depth of a dive was 42.2 m, and duration of dives ranged from 4 to 120 sec. We found that Pelagic Cormorants at Middleton Island were faithful to one particular foraging area and individuals dived in distinct patterns. Distinct, specialized foraging behavior may be advantageous in reducing intra- and interspecific competition but may also render the species vulnerable to changing environmental conditions.

Alaska↗
USGS2021

National Park Service Vegetation Mapping Inventory Program: Great Smoky Mountains National Park vegetation mapping project

The National Park Service (NPS) Vegetation Mapping Inventory (VMI) Program is an effort to classify, describe, and map existing vegetation communities in national park units throughout the United States. The NPS VMI Program is managed by the NPS Natural Resource Stewardship and Science Inventory and Monitoring Program and provides baseline vegetation information to natural resource managers, researchers, and ecologists. The U.S. Geological Survey Upper Midwest Environmental Sciences Center, NatureServe, and NPS Great Smoky Mountains National Park (GRSM, also referred to as the “Park”) have completed vegetation classification and mapping of GRSM, including the Foothills Parkway, for the NPS VMI Program. Mappers, ecologists, and botanists collaborated to affirm vegetation types of GRSM and to determine how best to map the vegetation types by using aerial imagery. A vegetation classification developed in 2003 by NatureServe and the NPS served as a foundation to further classify and map the vegetation types of the Park. Data from an additional 10 vegetation plots supported vegetation types either rare or not documented in the 2003 classification. Data from 203 verification sites were collected to test the field key to vegetation types and the application of vegetation types to a sample set of map polygons. Furthermore, data from 972 accuracy assessment (AA) sites were collected (of which 966 were used to test accuracy of the vegetation map layer). This GRSM vegetation mapping project identified 112 vegetation types consisting of 105 association types in the U.S. National Vegetation Classification (USNVC), 2 “park-special” types, 1 “map-special” type, and 4 cultural types in the USNVC. To map the vegetation and land cover of GRSM, 52 map classes were developed. Of these 52 map classes, 46 represent natural (including ruderal) vegetation types, most of which types are recognized in the USNVC. For the remaining 6 of the 52 map classes, 4 represent USNVC cultural types for agricultural and developed areas, and 2 represent non-USNVC types for nonvegetated open water and nonvegetated rock. Features were interpreted from viewing four-band digital aerial imagery using digital onscreen three-dimensional stereoscopic workflow systems in geographic information systems; digital aerial imagery was collected during September 23–October 30, 2015. The interpreted data were digitally and spatially referenced, thus making the spatial-database layers usable in a geographic information system. Polygon units were mapped to either a 0.5- or 0.25- hectare (ha) minimum mapping unit, depending on vegetation type. A geodatabase containing several feature-class layers and tables provides the locations and data of USNVC vegetation types (vegetation map layer), vegetation plots, verification sites, AA sites, project boundary extent, and aerial image centers and flight lines. Covering 210,875 ha, the feature-class layer and related tables for the vegetation map layer provide 34,084 polygons of detailed attribute data when special modifiers are not considered (average polygon size of 6.2 ha) and 36,589 polygons of detailed attribute data when special modifiers are considered (average polygon size of 5.8 ha). Each map polygon is assigned a map-class code and name and, when applicable, are linked to USNVC classification tables within the geodatabase. The vegetation map extent includes the administrative boundary for GRSM and the Foothills Parkway. A summary report, generated from the vegetation map layer, concludes that the 46 map classes representing natural (including ruderal) vegetation types apply to 99.2% of polygons (33,797 polygons; average size of 6.2 ha) and cover 98.6% of the Park (207,971.4 ha). Further broken down, map classes representing natural vegetation types indicate that the Park is 97.7% forest and woodland (205,882.5 ha), 0.6% shrubland (1,174.6 ha), and 0.4% herbaceous (914.3 ha). Map classes representing cultural vegetation types apply to 0.8% of polygons (259 polygons; average size of 4.9 ha) and cover 0.6% of the Park (1,277.4 ha). Map classes representing nonvegetation open and flowing water and unvegetated rock apply to 0.08% of polygons (28 polygons; average size of 58.1 ha) and cover 0.8% of the Park (1,625.9 ha). A thematic AA study was completed of map classes representing the natural (including ruderal) vegetation types of the Park. Initial AA results were discussed with NPS staff from the Park. Following input from NPS staff on how to handle map classes that fell below accuracy standards, adjustments were made to the vegetation map layer. Final results indicate an overall accuracy of 80.64% (kappa index of 79.96% for chance agreements) based on data from 966 of the 972 AA sites. Most individual map-class themes exceed the NPS VMI Program standard of 80% with a 90% confidence interval. The GRSM vegetation mapping project delivers many geospatial and vegetation data products, including an in-depth project report discussing methods and results, which includes map classification and map-class descriptions. This suite of products also includes descriptions and a field key to vegetation types; a database of vegetation plots, verification sites, and AA sites; digital images of field sites; field data sheets; digital aerial imagery; hardcopy and digital maps; a geodatabase of vegetation and land cover (map layer), field sites (vegetation plots, verification sites, and AA sites), aerial imagery index, project boundary, and metadata; and a contingency table listing AA results. Geospatial products are projected in the Universal Transverse Mercator, Zone 17 North, by using the North American Datum of 1983. Information on the NPS VMI Program and completed mapping projects are on the internet at https://www.nps.gov/im/vegetation-inventory.htm.

North Carolina, Tennessee↗
USGS2005

Paleoseismic study of the South Lajas fault: First documentation of an onshore Holocene fault in Puerto Rico

The island of Puerto Rico is located within the complex boundary between the North America and Caribbean plates. The relative motion along this boundary is dominantly left-lateral strike slip, but compression and extension are locally significant. Although tectonic models proposed for the region suggest the presence of onshore active faults in Puerto Rico, no faults with Holocene displacement have been documented on the island before this study. Current seismic hazard assessments primarily consider only the impact of distant, offshore seismic sources because onshore fault hazard is unknown. Our mapping and trenching studies demonstrate Holocene surface rupture on a previously undocumented fault in southwestern Puerto Rico. We excavated a trench across a scarp near the southern edge of the Lajas Valley that exposed a narrow fault zone disrupting alluvial deposits. Structural relations indicate valley-side-down fault slip, with a component of strike-slip motion. Radiocarbon analyses of organic material collected from the sediments suggest that the most recent surface rupture occurred during the past 5000 yr, but no minimum age has yet been established. This fault may be part of a larger fault zone that extends from the western end of the Lajas Valley toward Ponce, the second largest city in Puerto Rico. ?? 2005 Geological Society of America.

Special Paper of the Geological Society of America↗
USGS2009

Stratigraphic controls on saltwater intrusion in the Dominguez Gap area of coastal Los Angeles

The Los Angeles Basin is a densely populated coastal area that significantly depends on groundwater. A part of this groundwater supply is at risk from saltwater intrusion—the impetus for this study. High-resolution seismic-reflection data collected from the Los Angeles–Long Beach Harbor Complex have been combined with borehole geophysical and descriptive geological data from four nearby ~400-m-deep continuously cored wells and with borehole geophysical data from adjacent water and oil wells to characterize the Pliocene to Holocene stratigraphy of the Dominguez Gap coastal aquifer system. The new data are shown as a north-south, two- dimensional, sequence-stratigraphic model that is compared to existing lithostratigraphic models of the Los Angeles Basin in an attempt to better understand pathways of saltwater intrusion into coastal aquifers.

California↗
USGS1969

Geology and regional metamorphism of some high-grade cordierite gneisses, Front Range, Colorado

Cordierite is common in regional metamorphic gneisses of Precambrian age in the central part of the Front Range. It occurs in discontinuous stratigraphic units that are structurally a minor component, except locally, of the thick succession of biotite gneisses that comprise the widespread Idaho Springs Formation. The rocks have mineral assemblages, that are characteristic of the sillimanite grade of metamorphism. The cordierite occurs in three principal rock types: (1) potassic feldspar-bearing cordierite-garnet-sillimanite-biotite gneiss, (2) cordierite-biotite gneiss, and (3) cordierite-gedrite-biotite gneiss; each type contains several characteristic mineral assemblages. The rock types are gradational and overlap in areal distribution, and mainly owe their diversity in mineralogy to differences in bulk chemical composition. The field relations are consistent with an interpretation that the diverse cordierite rocks were derived from original sedimentary rocks, largely pelitic sediments. The potassic feldspar-bearing cordierite-garnet gneisses were formed from shales that contained more MgO and FeO than the more abundant sedimentary facies that yielded sillimanitic biotite gneisses. Cordierite-gedrite-biotite gneisses contain much aluminum, iron, and magnesium and little sodium and potassium as compared to the other biotite gneisses; they have an extremely low content of minor elements. Although their chemical compositions are unlike those of known modern sediments, the cordierite-gedrite gneisses are considered also to have been derived from sedimentary rocks. The physical properties and chemical compositions of the mineral phases vary somewhat from one rock type to another. Biotite varies systematically in composition, and the changes are closely related to rock type and thus to bulk composition; the MgO/FeO ratios range from 1.7 in the more mafic cordierite-gedrite rocks to 0.49 in potassic feldspar-bearing cordierite-garnet gneisses. Cordierite is magnesium-rich and intermediate in the range of composition of all analyzed cordierites (Leake, 1960); its MgO/FeO ratio is higher in the gedrite-bearing gneisses than in the potassic feldspar-bearing gneisses. The garnets consist dominantly of the almandine and pyrope molecules, and range from 64 to 75 percent almandine and from 14 to 27 pyrope. These crystals are zoned; their rims are slightly more ferrous and less magnesian than their cores. Both monoclinic and triclinic alkali feldspars coexist in the potassic feldspar-bearing cordierite-garnet gneisses. The potassic feldspars contain from 18 to 27 weight percent NaAlSi 3 O 8 . Plagioclase (oligoclase-andesine) is uncommon in the rocks. Gedrite has an MgO/FeO ratio ranging from 1 to 1.2. Associated minor minerals include iron oxides, andalusite, spinel and its alteration product högbomite, and corundum. The mineral assemblages can be correlated imperfectly with episodes of deformation and metamorphism. Relict staurolite and associated garnet occur locally as remnants of an assemblage formed early in regional metamorphism, presumably early in the first period of deformation. The dominant assemblage biotite-cordierite-garnet-magnetite-plagioclase-potassic feldspar-quartz-sillimanite and associated assemblages having fewer phases, were formed during period one and period two deformations, the principal episodes of regional dynamothermal metamorphism in the central part of the Front Range. A minor assemblage andalusite-biotite-magnetite-plagioclase-quartz was formed later, possibly coincident with a third period of deformation, largely cataclastic in effects, which was more local than the earlier deformations and metamorphism. Phase equilibria studies of the assemblage biotite-cordierite-garnet-magnetite-plagioclase-potassic feldspar-quartz-sillimanite and associated assemblages are interpreted to indicate that the cordierite assemblages approach a state of chemical equilibrium. The scatter of points in a distribution diagram can be interpreted in terms of at least two sets of equilibrium conditions that prevailed during the major plastic deformations. Other discrepancies indicating departure from a homogeneous equilibrium can be explained as a result of mosaic equilibrium involving limited diffusion of iron and magnesium for short distances. The mineral assemblages and the compositions of the ferromagnesian minerals in the cordierite rocks of this region are dependent primarily on the bulk composition of the rocks and variations in the mineral species that comprise the rocks and, to a lesser degree, on the grade of metamorphism. Biotite and cordierite are markedly more magnesian in the more mafic cordierite-gedrite-biotite gneiss than in the potassic feldspar-bearing cordierite-garnet-sillimanite-biotite gneiss. Associated microcline gneiss and biotite-sillimanite gneiss that contains muscovite as a primary stable mineral provides a means to define the metamorphic grade in the area of study. It is concluded from analyses of the assemblages with respect to theoretical phase relations in the system SiO 2 -Al 2 O 3 -Na 2 O-K 2 O-H 2 O that at least some of the rocks in the Central City-Nederland area are above the sillimanite-potassic feldspar isograd as defined by Evans and Guidotti (1966). In rocks of appropriate composition, muscovite is a stable phase in assemblages containing potassic feldspar and sillimanite. The cordierite assemblages and associated rocks are inferred to have formed in an environment having a load pressure of 3–5 kilobars (fluid pressure equaled load pressure) and a temperature somewhat in excess of 620° C.

Colorado↗
USGS1999

Data set incongruence and correlated character evolution: An example of functional convergence in the hind-limbs of stifftail diving ducks

The unwitting inclusion of convergent characters in phylogenetic estimates poses a serious problem for efforts to recover phylogeny. Convergence is not inscrutable, however, particularly when one group of characters tracks phylogeny and another set tracks adaptive history. In such cases, convergent characters may be correlated with one or a few functional anatomical units and readily identifiable by using comparative methods. Stifftail ducks (Oxyurinae) offer one such opportunity to study correlated character evolution and function in the context of phylogenetic reconstruction. Morphological analyses place stifftail ducks as part of a large clade of diving ducks that includes the sea ducks (Mergini), Hymenolaimus, Merganetta , and Tachyeres , and possibly the pochards (Aythyini). Molecular analyses, on the other hand, place stifftails far from other diving ducks and suggest, moreover, that stifftails are polyphyletic. Mitochondrial cytochrome b gene sequences of eight stifftail species traditionally supposed to form a clade were compared with each other and with sequences from 50 other anseriform and galliform species. Stifftail ducks are not the sister group of sea ducks but lie outside the typical ducks (Anatinae). Of the four traditional stifftail genera, monophyly of Oxyura and its sister group relationship with Nomonyx are strongly supported. Heteronetta probably is the sister group of that clade, but support is weak. Biziura is not a true stifftail. Within Oxyura , Old World species ( O. australis, O. leucocephala, O. maccoa ) appear to form a clade, with New World species ( O. jamaicensis, O. vittata ) branching basally. Incongruence between molecules and morphology is interpreted to be the result of adaptive specialization and functional convergence in the hind limbs of Biziura and true stifftails. When morphological characters are divided into classes, only hind-limb characters are significantly in conflict with the molecular tree. Likewise, null models of synonymous and nonsynonymous substitution based on patterns of codon-degeneracy and chemical dissimilarity indicate that the nucleotide and amino acid changes postulated by the molecular tree are more plausible than those postulated by the morphological tree. These findings teach general lessons about the utility of highly adaptive characters (in particular those related to foraging ecology) and underscore the problems that convergence can pose for attempts to recover phylogeny. They also demonstrate how the concept of natural data partitions and simple models of evolution (e.g., parsimony, likelihood, neutrality) can be used to test the accuracy of independent phylogenetic estimates and provide arguments in favor of one tree topology over another.

Systematic Biology↗
USGS1985

Rate and depth of pedogenic-carbonate accumulation in soils: Formation and testing of a compartment model.

The rate and depth of pedogenic carbonate accumulation in soils formed in Quaternary alluvium may be viewed as a theoretical problem that involves the mutual interaction of several independent and dependent soil-forming variables. We propose a model for carbonate accumulation in which the soil column is defined by a vertical sequence of 1-cm 2 -area compartments, each with a specified texture, bulk density, water-holding content, lithologic and mineralogic composition, soil-air pCO 2 , ionic strength, and temperature. On the basis of these data, rates of carbonate solubility and dissolution within a given compartment are determined. In arkosic to lithic arkosic sandy parent materials, high carbonate solubility (0.137 to 0.212 mg/ml) and the large reactive surface area of eolian calcareous dust result in rapid carbonate dissolution (0.79 to 9.92 × 10 −10 g/cm 2 /sec) that promotes rapid translocation of carbonate by infiltrating water. We derive a group of equations and use them to calculate net carbonate depletion or accumulation in a soil compartment over an interval of time as a function of the independent variables temperature and precipitation. These two variables largely determine or strongly influence soil-water balance, the external carbonate influx rate, and carbonate solubility. The carbonate distribution that our model predicts closely resembles the observed carbonate distribution in soils associated with Holocene deposits forming in arid, hyperthermic to xeric, thermic moisture-temperature regimes in southern California. This modeling indicates that with a mean carbonate influx rate of 1 × 10 −4 g/cm 2 /yr and in a semiarid, thermic climate, the maximum depression of the top of the Cca horizon is attained within only a few thousand years. In contrast, given the same influx rate, our model predicts that a noncalcareous B horizon cannot form in an arid, hyperthermic climate, a conclusion supported by field and laboratory studies of calcic soils in this climate. The influence of glacial-to-interglacial climatic changes on carbonate accumulation can be modeled by calculating latest Pleistocene soil-water balance with the aid of published estimates of full-glacial temperature and precipitation. On the basis of these modeling results, we propose that either of two types of glacial-to-interglacial climatic changes may account for the strongly bimodal, apparently polygenetic carbonate distribution that is observed in late Pleistocene soils of the eastern Mojave Desert of southern California. Such results of compartment-strategy modeling are encouraging and indicate the great potential of combined theoretical and empirical methods for considering pedological problems of interest to Quaternary geologists.

GSA Special Papers↗
USGS2023

Achieving success with RISE: A widely implementable, iterative, structured process for mastering interdisciplinary team science collaborations

Scientific experts from different disciplines often struggle to mesh their specialized perspectives into the shared mindset that is needed to address difficult and persistent environmental, ecological, and societal problems. Many traditional graduate programs provide excellent research and technical skill training. However, these programs often do not teach a systematic way to learn team skills, nor do they offer a protocol for identifying and tackling increasingly integrated interdisciplinary (among disciplines) and transdisciplinary (among researchers and stakeholders) questions. As a result, professionals trained in traditional graduate programs (e.g., current graduate students and employed practitioners) may not have all of the collaborative skills needed to advance solutions to difficult scientific problems. In the present article, we illustrate a tractable, widely implementable structured process called RISE that accelerates the development of these missing skills. The RISE process (Route to Identifying, learning, and practicing interdisciplinary and transdisciplinary team Skills to address difficult Environmental problems) can be used by diverse teams as a tool for research, professional interactions, or training. RISE helps professionals with different expertise learn from each other by repeatedly asking team-developed questions that are tested using an interactive quantitative tool (e.g., agent-based models, machine learning, case studies) applied to a shared problem framework and data set. Outputs from the quantitative tool are then discussed and interpreted as a team, considering all team members’ perspectives, disciplines, and expertise. After this synthesis, RISE is repeated with new questions that the team jointly identified in earlier data interpretation discussions. As a result, individual perspectives, originally informed by disciplinary training, are complemented by a shared understanding of team function and elevated interdisciplinary knowledge.

BioScience↗
USGS2014

Low-altitude photographic transects of the Arctic Network of National Park Units and Selawik National Wildlife Refuge, Alaska, July 2013

During July 16–18, 2013, low-level photography flights were conducted (with a Cessna 185 with floats and a Cessna 206 with tundra tires) over the five administrative units of the National Park Service Arctic Network (Bering Land Bridge National Preserve, Cape Krusenstern National Monument, Gates of the Arctic National Park and Preserve, Kobuk Valley National Park, and Noatak National Preserve) and the U.S. Fish and Wildlife Service’s Selawik National Wildlife Refuge in northwest Alaska, to provide images of current conditions and prevalence of land-cover types as a baseline for measuring future change, and to complement the existing grid-based sample photography of the region. Total flight time was 17 hours, 46 minutes, and total flight distance was 2,590 kilometers, at a mean altitude of about 300 meters above ground level. A total of 19,167 photographs were taken from five digital camera systems: 1. A Drift® HD-170 (focal length 5.00 mm); 2. A GoPro® Hero3 Black Edition (focal length 2.77 mm); 3. A Panasonic® Lumix DMC-FZ200 (24× superzoom with variable focal length); 4. A Panasonic® Lumix DMC-SZ7 (10x superzoom with variable focal length); and 5. A Canon® Rebel 3Ti with a Sigma zoom lens (18–200 mm focal length). The Drift® HD-170 and GoPro® Hero3 cameras were secured to the struts and underwing for nadir (direct downward) imaging. The Panasonic® and Canon® cameras were each hand-held for oblique-angle landscape images, shooting through the airplanes’ windows, targeting both general landscape conditions as well as landscape features of special interest, such as tundra fire scars and landslips. The Drift® and GoPro® cameras each were set for time-lapse photography at 5-second intervals for overlapping coverage. Photographs from all cameras (100 percent .jpg format) were date- and time-synchronized to geographic positioning system waypoints taken during the flights, also at 5-second intervals, providing precise geotagging (latitude-longitude) of all files. All photographs were adjusted for color saturation and gamma, and nadir photographs were corrected for lens distortion for the Drift® and GoPro® cameras’ 170° wide-angle distortion. EXIF (exchangeable image file format) data on camera settings and geotagging were extracted into spreadsheet databases. An additional 1 hour, 20 minutes, and 43 seconds of high-resolution videos were recorded at 60 frames per second with the GoPro® camera along selected transect segments, and also were image-adjusted and corrected for lens distortion. Geotagged locations of 12,395 nadir photographs from the Drift® and GoPro® cameras were overlayed in a geographic information system (ArcMap 10.0) onto a map of 44 ecotypes (land- and water-cover types) of the Arctic Network study area. Presence and area of each ecotype occurring within a geographic information system window centered on the location of each photograph were recorded and included in the spreadsheet databases. All original and adjusted photographs, videos, geographic positioning system flight tracks, and photograph databases are available by contacting ascweb@usgs.gov.

Alaska↗
USGS2021

An integrated path for spatial capture–recapture and animal movement modeling

Ecologists and conservation biologists increasingly rely on spatial capture–recapture (SCR) and movement modeling to study animal populations. Historically, SCR has focused on population-level processes (e.g., vital rates, abundance, density, and distribution), whereas animal movement modeling has focused on the behavior of individuals (e.g., activity budgets, resource selection, migration). Even though animal movement is clearly a driver of population-level patterns and dynamics, technical and conceptual developments to date have not forged a firm link between the two fields. Instead, movement modeling has typically focused on the individual level without providing a coherent scaling from individual- to population-level processes, whereas SCR has typically focused on the population level while greatly simplifying the movement processes that give rise to the observations underlying these models. In our view, the integration of SCR and animal movement modeling has tremendous potential for allowing ecologists to scale up from individuals to populations and advancing the types of inferences that can be made at the intersection of population, movement, and landscape ecology. Properly accounting for complex animal movement processes can also potentially reduce bias in estimators of population-level parameters, thereby improving inferences that are critical for species conservation and management. This introductory article to the Special Feature reviews recent advances in SCR and animal movement modeling, establishes a common notation, highlights potential advantages of linking individual-level (Lagrangian) movements to population-level (Eulerian) processes, and outlines a general conceptual framework for the integration of movement and SCR models. We then identify important avenues for future research, including key challenges and potential pitfalls in the developments and applications that lie ahead.

Ecology↗
USGS2006

The ionospheric impact on GPS performance in southern polar region

The primary objective of this paper is to present the results of the study of the effects of varying ionospheric conditions on the GPS signal tracking in the southern polar region. In the first stage of this study, the data collected by the OSU/USGS team in October-November 2003 within the TAMDEF (Transantarctic Mountains Deformation) network were used together with some IGS Antarctic stations to study the effect of severe ionospheric storms on GPS hardware. Note that TAMDEF is a joint USGS/OSU project with the primary objective of measuring crustal motion in the Transantarctic Mountains of Southern Victoria Land using GPS techniques. This study included ten Antarctic stations equipped with different dual-frequency GPS hardware, and the data were evaluated for two 24-hour periods of severe ionospheric storm (2003/10/29) and moderate ionospheric conditions (minor storm of 2003/11/11). The results of this study were presented at the LAG Assembly in Cairns, Australia (Grejner-Brzezinska et al., 2005). Additional tests, in a more controlled environment, were carried out at the US Antarctic station, McMurdo, between January 10 and February 6, 2006, under varying ionospheric conditions, where several different types of receivers were connected to the same antenna located on the rooftop of the Crary Laboratory (the primary test site). In this scenario, each antenna was subject to identical ionospheric effects during each day of the test, and no spatial decorrelation effects were present, as seen in the previous study, due to the spatial separation of the receivers tested. It should be noted, however, that no moderate or severe ionospheric storms occurred during the experiment, so, unfortunately, this type of conditions was not tested here. The test was repeated with different receivers connected to different antenna types; a total of four 5-day sessions were carried out. The following receiver types were used at the primary site: Trimble 5700, Ashtech Z-Surveyor, JNS Euro-80 and Novatel DL-4, with the following antennas: Trimble Zephyr Geodetic, Ashtech D/M and Ashtech E/M chokering. In addition, data collected by the MCM4 IGS station, MCMD UNAVCO station, and CRAR USGS station, all located within 300 m from the primary test site, were used in the analyses. These stations were equipped with the following receiver/antenna combinations: ADA SNR-12/AOAD/MJT chokering (MCM4), Trimble NETRS/AOAD/MJT chokering (MCMD), and TPS ODYSEY_E/JPSREGANT_DD_E (CRAR). The UNAVCO TEQC software was used to carry out the analyses. Depending on the data sampling rate and the mask angle, the expected numbers of observations per receiver/satellite were compared to the actual number of measurements collected during the ionospheric events, with a special emphasis on L2 data. A total number of cycle slips and losses of lock were computed and compared among the hardware types. The results presented here indicate that there is no significant effects on the GPS receivers during minor ionospheric storms (Kp<5). However, the results reported in ibid, indicate significant differences in the hardware performance under severe ionospheric storms. Thus, careful hardware selection is needed to assure data quality/continuity when observations may be affected by severe ionospheric disturbances, while under calm to minor ionospheric activity level there is no significant difference in performance among the hardware tested here.

Conference Paper↗