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Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

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At least 1,783 records · Page 99Linked to original sources
USGS2006

Fish community structure in freshwater karstic water bodies of the Sian Ka'an Reserve in the Yucatan peninsula, Mexico

We evaluated the relationship between limnetic characteristics and fish community structure (based on species richness, abundance and individual size) in contrasting but interconnected inland aquatic habitats of freshwater karstic wetlands in the Yucatan peninsula, Mexico. In the western hemisphere, freshwater karstic wetlands are found in south-eastern Mexico, northern Belize, western Cuba, Andros Island, Bahamas and the Everglades of southern Florida. Only in the Everglades have fish communities been well described. Karstic wetlands are typically oligotrophic because calcium carbonate binds phosphorus, making it relatively unavailable for plants. Fourteen permanent and seasonally flooded water bodies were sampled in both wet and dry seasons in Sian Ka'an Biosphere Reserve, in the Mexican state of Quintana Roo. Water systems were divided by morphology in four groups: cenotes with vegetation (CWV), cenotes without vegetation (CNV), wetlands (WTL), and temporal cenotes (TPC). Discriminant analysis based on physical characteristics such as turbidity, temperature, depth and oxygen confirmed that these habitats differed in characteristics known to influence fish communities. A sample-based rarefaction test showed that species richness was significantly different between water systems groups, showing that WTL and CWV had higher richness values than CNV and TPC. The most abundant fish families, Poeciliidae, Cichlidae and Characidae, differed significantly in average size among habitats and seasons. Seasonal and inter-annual variation, reflecting temporal variation in rainfall, strongly influenced the environmental differences between shallow and deep habitats, which could be linked to fish size and life cycles. Five new records of species were found for the reserve, and one new record for Quintana Roo state. ?? 2006 by Verlag Dr. Friedrich Pfeil.

Ichthyological Exploration of Freshwaters↗
USGS2007

Structure and composition of a watershed-scale sediment information network

A 'Watershed-Scale Sediment Information Network' (WaSSIN), designed to complement UNESCO's International Sedimentation Initiative, was endorsed as an initial project by the World Association for Sedimentation and Erosion Research. WaSSIN is to address global fluvial-sediment information needs through a network approach based on consistent protocols for the collection, analysis, and storage of fluvial-sediment and ancillary information at smaller spatial scales than those of the International Sedimentation Initiative. As a second step of implementation, it is proposed herein that the WaSSIN have a general structure of two components, (1) monitoring and data acquisition and (2) research. Monitoring is to be conducted in small watersheds, each of which has an established database for discharge of water and suspended sediment and possibly for bed load, bed material, and bed topography. Ideally, documented protocols have been used for collecting, analyzing, storing, and sharing the derivative data. The research component is to continue the collection and interpretation of data, to compare those data among candidate watersheds, and to determine gradients of fluxes and processes among the selected watersheds. To define gradients and evaluate processes, the initial watersheds will have several common attributes. Watersheds of the first group will be: (1) six to ten in number, (2) less than 1000 km2 in area, (3) generally in mid-latitudes of continents, and (4) of semiarid climate. Potential candidate watersheds presently include the Weany Creek Basin, northeastern Australia, the Zhi Fanggou catchment, northern China, the Eshtemoa Watershed, southern Israel, the Metsemotlhaba River Basin, Botswana, the Aiuaba Experimental Basin, Brazil, and the Walnut Gulch Experimental Watershed, southwestern United States.

International Journal of Sediment Research↗
USGS2011

Keeping Hawai’i’s forest birds one step ahead of avian diseases in a warming world: a focus on Hakalau Forest National Wildlife Refuge. A case study from the National Conservation and Training Center Structured Decision Making Workshop

This report is a product of a one-week workshop on using Structured Decision Making to identify and prioritize conservation actions to address the threat of climate change on Hawaii‟s native forest bird community. Specifically, t his report addresses the issue of global warming ‟s likely role in increasing disease prevalence in upper elevation forests of Hawaii, negatively impacting native bird populations susceptible to the disease but currently disease - free because of the cooler temperatures at high elevations.

Hawaii↗
USGS2013

Population genetic structure of rare and endangered plants using molecular markers

This study was initiated to assess the levels of genetic diversity and differentiation in the remaining populations of Phyllostegia stachyoides and Melicope zahlbruckneri in Hawai`i Volcanoes National Park and determine the extent of gene flow to identify genetically distinct individuals or groups for conservation purposes. Thirty-six Amplified Fragment Length Polymorphic (AFLP) primer combinations generated a total of 3,242 polymorphic deoxyribonucleic acid (DNA) fragments in the P. stachyoides population with a percentage of polymorphic bands (PPB) ranging from 39.3 to 65.7% and 2,780 for the M. zahlbruckneri population with a PPB of 18.8 to 64.6%. Population differentiation (Fst) of AFLP loci between subpopulations of P. stachyoides was low (0.043) across populations. Analysis of molecular variance of P. stachyoides showed that 4% of the observed genetic differentiation occurred between populations in different k ī puka and 96% when individuals were pooled from all k ī puka. Moderate genetic diversity was detected within the M. zahlbruckneri population. Bayesian and multivariate analyses both classified the P. stachyoides and M. zahlbruckneri populations into genetic groups with considerable sub-structuring detected in the P. stachyoides population. The proportion of genetic differentiation among populations explained by geographical distance was estimated by Mantel tests. No spatial correlation was found between genetic and geographic distances in both populations. Finally, a moderate but significant gene flow that could be attributed to insect or bird-mediated dispersal of pollen across the different k ī puka was observed. The results of this study highlight the utility of a multi-allelic DNA-based marker in screening a large number of polymorphic loci in small and closely related endangered populations and revealed the presence of genetically unique groups of individuals in both M. zahlbruckneri and P. stachyoides populations. Based on these findings, approaches that can assist conservation efforts of these species are proposed.

Hawai`i↗
USGS1989

Structural evolution of the southeastern portion of the Anadarko Basin region

Field investigations in the Lake Classen-Turner Falls, Oklahoma, area of the northern Arbuckle anticline, on the southeastern margin of the Anadarko basin, indicate that transpressional (oblique compressional) deformation of Late Pennsylvanian age dominated the structural development of this area. The Arbuckle anticline is detached along the NW -trending, SW -dipping, left-reverse Arbuckle fault and is thrust obliquely onto the margin of the Tishomingo block to the east. Paleostress analysis of slip lines on mesoscopic faults along the northeastern limb of the Arbuckle anticline, associated in style and geometry with oblique Arbuckle thrusting, indicates compression directed N. 35-60° E.

Oklahoma↗
USGS2014

Thresholds for conservation and management: structured decision making as a conceptual framework

A conceptual framework is provided for considering the threshold concept in natural resource management and conservation. We define three kinds of thresholds relevant to management and conservation. Ecological thresholds are values of system state variables at which small changes bring about substantial or specified changes in system dynamics. They are frequently incorporated into ecological models used to project system responses to management actions. Utility thresholds are components of management objectives and are values of state or performance variables at which small changes yield substantial changes in the value of the management outcome. Decision thresholds are values of system state variables at which small changes prompt changes in management actions in order to reach specified management objectives. Decision thresholds are derived from the other components of the decision process.We advocate a structured decision making (SDM) approach within which the following components are identified: objectives (possibly including utility thresholds), potential actions, models (possibly including ecological thresholds), monitoring program, and a solution algorithm (which produces decision thresholds). Adaptive resource management (ARM) is described as a special case of SDM developed for recurrent decision problems that are characterized by uncertainty. We believe that SDM, in general, and ARM, in particular, provide good approaches to conservation and management. Use of SDM and ARM also clarifies the distinct roles of ecological thresholds, utility thresholds, and decision thresholds in informed decision processes.

Book↗
USGS2014

Arthropod community structure on bark of koa ( Acacia koa ) and ʻōhiʻā ( Metrosideros polymorpha ) at Hakalau Forest National Wildlife Refuge, Hawaiʻi Island, Hawaiʻi

The arthropod community associated with tree bark contains a wide variety of taxa but is poorly described, particularly in Hawaiʽi. Our overall goals were to evaluate the abundance of arthropods available to foraging birds and how variation in bark substrates may contribute to arthropod distributions in native forests. Our study aimed to identify this fauna on the dominant canopy-forming trees koa ( Acacia koa ) and ʽōhiʽa ( Metrosideros polymorpha ) within wet montane forest at Hakalau Forest National Wildlife Refuge, Hawaiʽi Island. At two sites roughly similar in elevation and habitat structure, we deployed three trap types designed to intercept arthropods moving along bark within tree canopies: a bole trap based on a pre-existing design and two traps specially designed for this study. Bole traps were placed on koa and ʽōhiʽa while branch traps were established on large and small branches of ʽōhiʽa. In total, 15 arthropod orders were identified, with Collembola most abundant (number/trap-day) generally followed by Isopoda and Araneae. Differences in abundance were found in some instances, but overall, few differences were detected between tree species or sites. Relative abundances of arthropod groups were also generally similar between trees and sites and among different parts of ʽōhiʽa. These results indicate that bark-dwelling arthropod communities are similar on koa and ʽōhiʽa, and birds should not develop strong preferences for gleaning arthropods from the bark of either species of tree based on prey availability.

Hawai'i↗
USGS2014

Lake Michigan offshore ecosystem structure and food web changes from 1987 to 2008

Ecosystems undergo dynamic changes owing to species invasions, fisheries management decisions, landscape modifications, and nutrient inputs. At Lake Michigan, new invaders (e.g., dreissenid mussels ( Dreissena spp.), spiny water flea ( Bythotrephes longimanus ), round goby ( Neogobius melanostomus )) have proliferated and altered energy transfer pathways, while nutrient concentrations and stocking rates to support fisheries have changed. We developed an ecosystem model to describe food web structure in 1987 and ran simulations through 2008 to evaluate changes in biomass of functional groups, predator consumption, and effects of recently invading species. Keystone functional groups from 1987 were identified as Mysis , burbot ( Lota lota ), phytoplankton, alewife ( Alosa pseudoharengus ), nonpredatory cladocerans, and Chinook salmon (Oncorhynchus tshawytscha ). Simulations predicted biomass reductions across all trophic levels and predicted biomasses fit observed trends for most functional groups. The effects of invasive species (e.g., dreissenid grazing) increased across simulation years, but were difficult to disentangle from other changes (e.g., declining offshore nutrient concentrations). In total, our model effectively represented recent changes to the Lake Michigan ecosystem and provides an ecosystem-based tool for exploring future resource management scenarios.

Lake Michigan↗
USGS2015

Structural equation modeling: Building and evaluating causal models

Scientists frequently wish to study hypotheses about causal relationships, rather than just statistical associations. This chapter addresses the question of how scientists might approach this ambitious task. Here we describe structural equation modeling (SEM), a general modeling framework for the study of causal hypotheses. Our goals are to (a) concisely describe the methodology, (b) illustrate its utility for investigating ecological systems, and (c) provide guidance for its application. Throughout our presentation, we rely on a study of the effects of human activities on wetland ecosystems to make our description of methodology more tangible. We begin by presenting the fundamental principles of SEM, including both its distinguishing characteristics and the requirements for modeling hypotheses about causal networks. We then illustrate SEM procedures and offer guidelines for conducting SEM analyses. Our focus in this presentation is on basic modeling objectives and core techniques. Pointers to additional modeling options are also given.

Book chapter↗
USGS1988

Extracting topographic structure from digital elevation data for geographic information-system analysis

Software tools have been developed at the U.S. Geological Survey's EROS Data Center to extract topographic structure and to delineate watersheds and overland flow paths from digital elevation models. The tools are specialpurpose FORTRAN programs interfaced with general-purpose raster and vector spatial analysis and relational data base management packages. The first phase of analysis is a conditioning phase that generates three data sets: the original OEM with depressions filled, a data set indicating the flow direction for each cell, and a flow accumulation data set in which each cell receives a value equal to the total number of cells that drain to it. The original OEM and these three derivative data sets can then be processed in a variety of ways to optionally delineate drainage networks, overland paths, watersheds for userspecified locations, sub-watersheds for the major tributaries of a drainage network, or pour point linkages between watersheds. The computer-generated drainage lines and watershed polygons and the pour point linkage information can be transferred to vector-based geographic information systems for futher analysis. Comparisons between these computergenerated features and their manually delineated counterparts generally show close agreement, indicating that these software tools will save analyst time spent in manual interpretation and digitizing.

Photogrammetric Engineering and Remote Sensing↗
USGS2015

Aluminosilicate melts and glasses at 1 to 3 GPa: Temperature and pressure effects on recovered structural and density changes

In the pressure range in the Earth’s mantle where many basaltic magmas are generated (1 to 3 GPa) (Stolper et al. 1981), increases in the coordination numbers of the network-forming cations in aluminosilicate melts have generally been considered to be minor, although effects on silicon and particularly on aluminum coordination in non-bridging oxygen-rich glasses from the higher, 5 to 12 GPa range, are now well known. Most high-precision measurements of network cation coordination in such samples have been made by spectroscopy (notably 27 Al and 29 Si NMR) on glasses quenched from high-temperature, high-pressure melts synthesized in solid-media apparatuses and decompressed to room temperature and 1 bar pressure. There are several effects that could lead to the underestimation of the extent of actual structural (and density) changes in high-pressure/temperature melts from such data. For non-bridging oxygen-rich sodium and calcium aluminosilicate compositions in the 1 to 3 GPa range, we show here that glasses annealed near to their glass transition temperatures systematically record higher recovered increases in aluminum coordination and in density than samples quenched from high-temperature melts. In the piston-cylinder apparatus used, rates of cooling through the glass transition are measured as very similar for both higher and lower initial temperatures, indicating that fictive temperature effects are not the likely explanation of these differences. Instead, transient decreases in melt pressure during thermal quenching, which may be especially large for high initial run temperatures, of as much as 0.5 to 1 GPa, may be responsible. As a result, the equilibrium proportion of high-coordinated Al in this pressure range may be 50 to 90% greater than previously estimated, reaching mean coordination numbers (e.g., 4.5) that are probably high enough to significantly affect melt properties. New data on jadeite (NaAlSi 2 O 6 ) glass confirm that aluminum coordination increase with pressure is inhibited in compositions low in non-bridging O atoms.

American Mineralogist↗
USGS2012

Avian community responses to vegetation structure within chained and hand-cut pinyon-juniper woodlands on the Colorado Plateau

We investigated relationships between breeding birds and vegetation characteristics in fuels-reduction treatment areas within pinyon-juniper woodlands at locations over the Colorado Plateau. The goal of this study was to document differences in avian community responses to two types of pinyon-juniper fuels-reduction treatments (chained vs. hand-cut), relative to control sites. We selected 73 vegetation plots in southern Utah and northern Arizona, of which 33 had been previously thinned by handcutting or chaining, and 40 control plots in untreated pinyon-juniper woodlands. At the 73 locations we documented vegetation structure and counted birds within 3.1 ha circular plots during the 2005 and 2006 breeding seasons. We focused in particular on the effects of fuels-reduction treatments to 16 bird species that are considered pinyon-juniper obligates. We found that density of pinyon pines was the most important variable in predicting bird species richness in all treatments and at control sites. Abundance of Brewer&rsquo;s Sparrow (<i>Spizella breweri</i>) was negatively related to chained, but positively related to hand cut areas. Vesper Sparrow (<i>Poocetes graminius</i>) abundance was negatively related to both chaining and handcutting. Within 16 pinyon-juniper obligate bird species, abundance of five was positively related to pinyon-pine density, while two were positively related to juniper density. These responses, along with other bird-vegetation relationships influenced by treatment type, need to be considered by land managers when planning fuels reduction treatments in pinyon-juniper woodland habitat in the Colorado Plateau.

Arizona, Colorado, New Mexico, Utah↗
USGS2012

Design and implementation of a structural health monitoring and alerting system for hospital buildings in the United States

This paper describes the current progress in the development of a structural health monitoring and alerting system to meet the needs of the U.S. Department of Veterans Affairs to monitor hospital buildings instrumented in high and very high seismic hazard regions in the U.S. The system, using the measured vibration data, is primarily designed for post-earthquake condition assessment of the buildings. It has two essential components &ndash; sensing and analysis. The sensing component includes all necessary firmware and sensors to measure the response of the building; while the analysis component consists of several data processing modules integrated into an open source software package which compresses a large amount of measured data into useful information to assess the building&rsquo;s condition before and after an event. The information can be used for a rapid building safety assessment, and to support decisions for necessary repairs, replacements, and other maintenance and rehabilitation measures.

Conference Paper↗
USGS2015

Integrated thermal infrared imaging and Structure-from-Motion photogrametry to map apparent temperature and radiant hydrothermal heat flux at Mammoth Mountain, CA USA

This work presents a method to create high-resolution (cm-scale) orthorectified and georeferenced maps of apparent surface temperature and radiant hydrothermal heat flux and estimate the radiant hydrothermal heat emission rate from a study area. A ground-based thermal infrared (TIR) camera was used to collect (1) a set of overlapping and offset visible imagery around the study area during the daytime and (2) time series of co-located visible and TIR imagery at one or more sites within the study area from pre-dawn to daytime. Daytime visible imagery was processed using the Structure-from-Motion photogrammetric method to create a digital elevation model onto which pre-dawn TIR imagery was orthorectified and georeferenced. Three-dimensional maps of apparent surface temperature and radiant hydrothermal heat flux were then visualized and analyzed from various computer platforms (e.g., Google Earth, ArcGIS). We demonstrate this method at the Mammoth Mountain fumarole area on Mammoth Mountain, CA. Time-averaged apparent surface temperatures and radiant hydrothermal heat fluxes were observed up to 73.7 oC and 450 W m-2, respectively, while the estimated radiant hydrothermal heat emission rate from the area was 1.54 kW. Results should provide a basis for monitoring potential volcanic unrest and mitigating hydrothermal heat-related hazards on the volcano.

California↗
USGS2009

Temporal characteristics of coherent flow structures generated over alluvial sand dunes, Mississippi River, revealed by acoustic doppler current profiling and multibeam echo sounding

This paper investigates the flow in the lee of a large sand dune located at the confluence of the Mississippi and Missouri Rivers, USA. Stationary profiles collected from an anchored boat using an acoustic Doppler current profiler (ADCP) were georeferenced with data from a real-time kinematic differential global positioning system. A multibeam echo sounder was used to map the bathymetry of the confluence and provided a morphological context for the ADCP measurements. The flow in the lee of a low-angle dune shows good correspondence with current conceptual models of flow over dunes. As expected, quadrant 2 events (upwellings of low-momentum fluid) are associated with high backscatter intensity. Turbulent events generated in the lower lee of a dune near the bed are associated with periods of vortex shedding and wake flapping. Remnant coherent structures that advect over the lower lee of the dune in the upper portion of the water column, have mostly dissipated and contribute little to turbulence intensities. The turbulent events that occupy most of the water column in the upper lee of the dune are associated with periods of wake flapping.

Missouri↗
USGS2008

Riparian plant community structure in a managed hydrological regime

The hydrology of the Snake River in Grand Teton National Park is partly determined by releases from Jackson Lake Dam. The dam was first built in 1908 and became part of the National Park system when GTNP was expanded to include most of Jackson Hole. Completion of the present structure of Jackson Lake Dam occurred in 1917 and resulted in an increase above the natural level of Jackson Lake of 11.9 m. The Bureau of Reclamation (BOR) manages the dam and sets discharge schedules, primarily to meet agricultural needs, and to a lesser extent the needs of recreational river use. Major changes to the hydrological regime of the Snake River include lower than natural peak releases, decrease in frequency of extreme flood events , and unusually high flows from July to September. In addition , peak releases prior to 1957 were not synchronized with spring runoff but shifted to July or early August. Changes in inundation frequencies of floodplains , inundation duration and timing of peak flows have profound effects on the extent and composition of the riparian zone.

Wyoming↗
USGS1973

Petrography and structural relations of granitic basement rocks in the Monterey Bay area, California

In the past, the granitic basement of the Coast Ranges has been thought to be dominantly quartz diorite and low in K-feldspar. However, a study of outcrops around Monterey Bay, basement well samples, and dredge samples from Monterey Bay shows that the granitic basement averages about 15 to 20 percent K-feldspar. Therefore, as a sedimentary provenance, the basement around Monterey Bay could have contributed abundant K-feldspar to the Cenozoic sedimentary deposits of the region; that is, in the Monterey Bay area the local basement is an adequate source for the abundant K-feldspar in the sedimentary units. The distribution of basement rocks and mapped faults, coupled with gravity-geophysical data, suggests that the area between the San Andreas and Sur-Nacimiento fault zones (the Salinian block) near Monterey Bay is broken into several discrete structural blocks. Some of these blocks juxtapose not only different basement rocks, but also different contour patterns on the buried basement surface. These features suggest large strike-slip movements along some faults within the Salinian block in the Monterey Bay area.

California↗