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At least 1,171 records · Page 65Linked to original sources

USGS2015

Biogeochemical aspects of uranium mineralization, mining, milling, and remediation

Natural uranium (U) occurs as a mixture of three radioactive isotopes: 238 U, 235 U, and 234 U. Only 235 U is fissionable and makes up about 0.7% of natural U, while 238 U is overwhelmingly the most abundant at greater than 99% of the total mass of U. Prior to the 1940s, U was predominantly used as a coloring agent, and U-bearing ores were mined mainly for their radium (Ra) and/or vanadium (V) content; the bulk of the U was discarded with the tailings (Finch et al., 1972). Once nuclear fission was discovered, the economic importance of U increased greatly. The mining and milling of U-bearing ores is the first step in the nuclear fuel cycle, and the contact of residual waste with natural water is a potential source of contamination of U and associated elements to the environment. Uranium is mined by three basic methods: surface (open pit), underground, and solution mining (in situ leaching or in situ recovery), depending on the deposit grade, size, location, geology and economic considerations (Abdelouas, 2006). Solid wastes at U mill tailings (UMT) sites can include both standard tailings (i.e., leached ore rock residues) and solids generated on site by waste treatment processes. The latter can include sludge or “mud” from neutralization of acidic mine/mill effluents, containing Fe and a range of coprecipitated constituents, or barium sulfate precipitates that selectively remove Ra (e.g., Carvalho et al., 2007). In this chapter, we review the hydrometallurgical processes by which U is extracted from ore, the biogeochemical processes that can affect the fate and transport of U and associated elements in the environment, and possible remediation strategies for site closure and aquifer restoration. This paper represents the fourth in a series of review papers from the U.S. Geological Survey (USGS) on geochemical aspects of UMT management that span more than three decades. The first paper (Landa, 1980) in this series is a primer on the nature of tailings and radionuclide mobilization from them. The second paper (Landa, 1999) includes coverage of research carried out under the U.S. Department of Energy’s Uranium Mill Tailings Remedial Action Program (UMTRA). The third paper (Landa, 2004) reflects the increased focus of researchers on biotic effects in UMT environs. This paper expands the focus to U mining, milling, and remedial actions, and includes extensive coverage of the increasingly important alkaline in situ recovery and groundwater restoration.

Applied Geochemistry↗

USGS2018

Use of created snags by cavity‐nesting birds across 25 years

Snags are important habitat features for many forest‐dwelling species, so reductions in the number of snags can lead to the loss of biodiversity in forest ecosystems. Intentional snag creation is often used in managed forests to mitigate the long‐term declines of naturally created snags, yet information regarding the use of snags by wildlife across long timescales (>20 yr) is lacking and prevents a complete understanding of how the value of created snags change through time. We used a long‐term experiment to assess how harvest treatment (i.e., small‐patch group selection, 2‐story, and clearcut) and snag configuration (i.e., scattered and clustered) influenced nesting in and foraging on 25–27‐year‐old Douglas‐fir ( Pseudotsuga menziesii ) snags by cavity‐nesting birds. In addition, we compared our contemporary measures of bird use to estimates obtained from historical surveys conducted on the same group of snags to quantify how bird use changed over time. Despite observing created snags for >750 hours across 2 consecutive breeding seasons, we found limited evidence of nesting activity. Only 11% of created snags were used for breeding, with nesting attempts by 4 bird species ( n = 36 nests); however, we detected 12 cavity‐nesting species present on our study sites. Furthermore, nearly all nests (94%) belonged to the chestnut‐backed chickadee ( Poecile rufescens ), a weak cavity‐excavating species that requires well‐decayed wood for creating nest cavities. Our surveys also recorded few observations of birds using created snags as foraging substrates, with only 1 foraging event recorded for every 20 hours of observation. We detected 82% fewer nests and recorded 7% fewer foraging observations during contemporary field work despite spending >7.5 times more effort observing created snags relative to historical surveys. We conclude that 25–27‐year‐old created Douglas‐fir snags provided limited opportunities for nesting and foraging by most cavity‐nesting birds, and that the period of greatest use by this group occurred within 5–15 years of creation.

Journal of Wildlife Management↗

USGS2012

Estimating occupancy in large landscapes: evaluation of amphibian monitoring in the greater Yellowstone ecosystem

Monitoring of natural resources is crucial to ecosystem conservation, and yet it can pose many challenges. Annual surveys for amphibian breeding occupancy were conducted in Yellowstone and Grand Teton National Parks over a 4-year period (2006–2009) at two scales: catchments (portions of watersheds) and individual wetland sites. Catchments were selected in a stratified random sample with habitat quality and ease of access serving as strata. All known wetland sites with suitable habitat were surveyed within selected catchments. Changes in breeding occurrence of tiger salamanders, boreal chorus frogs, and Columbia-spotted frogs were assessed using multi-season occupancy estimation. Numerous a priori models were considered within an information theoretic framework including those with catchment and site-level covariates. Habitat quality was the most important predictor of occupancy. Boreal chorus frogs demonstrated the greatest increase in breeding occupancy at the catchment level. Larger changes for all 3 species were detected at the finer site-level scale. Connectivity of sites explained occupancy rates more than other covariates, and may improve understanding of the dynamic processes occurring among wetlands within this ecosystem. Our results suggest monitoring occupancy at two spatial scales within large study areas is feasible and informative.

Wyoming↗

USGS2013

Riparian restoration in the context of Tamarix control in the western United States: Chapter 23

This chapter focuses on the restoration of riparian systems in the context of Tamarix control—that is, Tamarix -dominated sites are converted to a replacement vegetation type that achieves specific management goals and helps return parts of the system to a desired and more natural state or dynamic. It reviews research related to restoring native riparian vegetation following tamarix control or removal. The chapter begins with an overview of objective setting and the planning of tamarix control and proceeds by emphasizing the importance of considering site-specific factors and of context in selecting and prioritizing sites for restoration. In particular, it considers valley and bottomland geomorphology, along with river flow regime and associated fluvial disturbance, surface water and groundwater availability, and soil salinity and texture. The chapter concludes with a discussion of costs and benefits associated with active, passive, and combined ecological restoration approaches, as well as the key issues to consider in carrying out restoration projects at a range of scales.

Book chapter↗

USGS2010

Demographic differences of black-capped vireos in 2 habitat types in central Texas

To understand the effects of habitat selection, we analyzed differences in abundance, age structure, and nesting success of black-capped vireos (Vireo atricapilla) in 2 early successional habitat types found on Fort Hood, a 87,890-ha Military Reservation in central Texas, USA. These habitats were 1) large areas of continuously shrubby vegetation (both natural and mechanically made), referred to as shrubland habitat, and 2) anthropogenically created small patches of shrubby vegetation centered on one or several large trees, known locally as donut habitat. The objectives of our study were to determine whether there were differences in abundance, age structure, and daily nest survival in these 2 habitat types and to determine whether donut habitat is high- or low-quality habitat. Donut habitat had a lower abundance of vireos (half as many as shrubland/point count) and a higher percentage of second-year males, suggesting donut habitat was lower-quality habitat than shrubland. Analyses of daily nest survival indicated that habitat, nest height, and year were all important variables. Nests initiated in 2004, located in shrubland habitats, and higher from the ground were more likely to succeed. Our study provided evidence that habitat is a limiting factor for this federally endangered species. Because habitat is limiting, wildlife biologists at Fort Hood should focus on managing higher quality, contiguous shrubland habitat. Wildlife biologists should also continue to monitor areas of donut habitat to determine whether they represent potential population sinks.

Journal of Wildlife Management↗

USGS1989

Studies of geology and hydrology in the Basin and Range Province, Southwestern United States, for isolation of high-level radioactive waste - Basis of characterization and evaluation

The geologic and hydrologic factors in selected regions of the Basin and Range province were examined to identify prospective areas for further study that may provide isolation of high-level radioactive waste from the accessible environment. The six regions selected for study were characterized with respect to the following guidelines: (1) Potential repository media; (2) Quaternary tectonic conditions; (3) climatic change and geomorphic processes; (4) ground-water conditions; (5) ground-water quality; and (6) mineral and energy resources. The repository medium will function as the first natural barrier to radionuclide travel by virtue of associated slow ground-water velocity. The principal rock types considered as host media include granitic, intermediate, and mafic intrusive rocks; argillaceous rocks; salt and anhydrite; volcanic mudflow (laharic) breccias; some intrusive rhyolitic plugs and stocks; partially zeolitized tuff; and metamorphic rocks. In the unsaturated zone, the permeability and hydrologic properties of the rocks and the hydrologic setting are more important than the rock type. Media ideally should be permeable to provide drainage and should have a minimal water flux The ground-water flow path from a repository to the accessible environment needs to present major barriers to the transport of radionuclides. Factors considered in evaluating the ground-water conditions include ground-water traveltimes and quality, confining beds, and earth materials favorable for retardation of radionuclides. Ground-water velocities in the regions were calculated from estimated hydraulic properties of the rocks and gradients. Because site-specific data on hydraulic properties are not available, data from the literature were assembled and synthesized to obtain values for use in estimating ground-water velocities. Hydraulic conductivities for many rock types having granular and fracture permeability follow a log-normal distribution. Porosity for granular and very weathered crystalline rock tends to be normally distributed; porosity of fractured crystalline rock probably follows a log-normal distribution. The tectonic setting needs to prevent an increase in radionuclides to the accessible environment. Data on historic seismicity and heat flow, Quaternary faults, volcanism, and uplift were used to assess the tectonic conditions. Long-term late Cenozoic rates of vertical crustal movement in the Basin and Range province range from less than 2 meters per 104 years to greater than 20 meters per 104 years. Shortterm rates of vertical movement may be more than an order of magnitude greater, based on geodetic leveling. Changes in tectonic and climatic processes may potentially cause changes in hydrologic conditions and geomorphology that could affect the integrity of a deep, mined repository either adversely or beneficially. The transition from a full-glacial climate to the current interglacial condition has occurred within the past 15,000 years. Reconstructions of the last full-glacial climate indicate that, at that time, there was greater water availability for runoff and vegetation growth than there is now. Based on the increased water availability and depending on seasonal distribution of precipitation, on soil characteristics, on topography, and on other characteristics, ground-water recharge during the full-glacial climate is estimated to have been possibly 2 to 10 or more times the modern rate. During the full-glacial climate, more than 100 lakes occupied closed basins in the province. Any increase in ground-water recharge and refilling of Pleistocene lakes will tend to decrease the distance of ground-water flow and its time of travel. The unsaturated zone this zone is considered a potential host medium where the thickness is greater than 150 m will be decreased by these changes. In contrast, incision of streams and other geomorphic, tectonic, or climatically induced changes that lower the ground-water discharge level will tend to increase the thickness of the unsaturated zone. Aggradation in basinal troughs may either decrease or increase the thickness of the unsaturated zone. Aggradation in basins that causes the ground-water discharge level to rise will tend to decrease the thickness of unsaturated zone in the adjacent uplands; aggradation in basins where the ground-water discharge level remains the same or is lowered will increase the unsaturated thickness of basin fill. Records show that, throughout late Cenozoic time in the Basin and Range province, continued vertical crustal movements have tended to maintain mountain ranges and closed basins, whereas aggradation of the basins and erosion of the mountain ranges have tended to decrease the topographic relief. Maximum rates of denudation for small basins in areas climatically similar to the Basin and Range province are about 2 meters per 104 years. For sites unaffected by stream incision and scarp retreat, a conservative estimate of erosion affecting long-term changes in depth of burial would appear to be 2 meters per 104 years, or, equal to the long-term rate of vertical crustal movement where greater than 2 meters per 104 years. The response of the ground-water conditions to climatic and geomorphically induced boundary conditions is significant from the points of: (1) The potential maximum change in the ground-water flow system; (2) the time of response of the ground-water system; and (3) the present state of the ground-water system as a result of past changes. Effects of longterm climatic and tectonic changes on hydrologic and geomorphic conditions differ from area to area, and rates of change of geomorphic and hydrologic conditions may vary significantly. Therefore, sitespecific studies need to be made to assess the long-term integrity of deep, mined repositories.

Arizona, California, Idaho, Nevada, New Mexico, Te↗

USGS2003

Surface-water hydrology of the Gulf Intracoastal Waterway in South-Central Louisiana, 1996-99

The flow of freshwater and suspended sediment from the Lower Atchafalaya River (LAR) and Wax Lake Outlet (WLO) into and along the Gulf Intracoastal Waterway (GIWW) and selected adjacent surface-water bodies between Cypremort and Larose in south-central Louisiana, from October 1996 to December 1999, was characterized using instantaneous and computed continuous discharge measurements and measurements of suspended- sediment concentrations. The GIWW parallels the entire Louisiana coast near the wetland/ upland interface. Following natural hydraulic gradients, the GIWW captures water and sediment from the southward flowing LAR and the WLO where it crosses those waterways, and distributes this freshwater and sediment to points east and west. East of Morgan City, La., an average of 12,200 ft3/s (cubic feet per second) of water flowed from the LAR into the Avoca Island Cutoff Channel. The LAR was the primary source of water to the GIWW east of Morgan City. Drainage from the Verret Subbasin through Bayou Boeuf contributed an average of 1,000 ft3/s to the eastward flow in the GIWW. Eastward flow in the GIWW near Bay Wallace east of Morgan City and to the west of the Houma Navigation Canal (HNC) at Houma, La., averaged about 5,700 ft3/s. Average flow in the GIWW east of the HNC at Houma was 2,610 ft3/s to the east, and 2,200 ft3/s east of Bayou Lafourche at Larose, also to the east. Measured discharge in the GIWW was always to the west between the LAR and WLO. Water entered this stretch of the GIWW from the LAR. The WLO was the primary source of water to the GIWW west of WLO. Discharge in the GIWW averaged 9,460 ft3/s west of WLO south of Calumet and 8,230 ft3/s east of Jaws Bay west of Franklin. Average discharge in the GIWW west of Jaws Bay near Cypremort was 3,310 ft3/s and at Cypremort was 1,350 ft3/s. Average discharge was to the west at all four locations, but discharge as high as 2,830 ft3/s was measured flowing eastward toward Jaws Bay in the GIWW at Cypremort. In bayous and canals in most of coastal Louisiana, including the GIWW, stage narrowly fluctuates around the Gulf of Mexico level. Where the GIWW crosses the LAR and WLO, stage can reach 3 ft (feet) or more above the North American Vertical Datum of 1988 (NAVD88). Flow in the GIWW results from these differences in stage. When the LAR at Morgan City reached 3 to 4 ft above NAVD88, flow in the GIWW became more predictable. Discharge at most sites between the HNC and Jaws Bay increased in varying amounts as stage of the LAR at Morgan City increased beyond 3 ft above NAVD88. At sites in the GIWW east of HNC, discharge did not increase predictably. For all measurements made when the LAR at Morgan City was 3 ft or more above NAVD88, average discharge was about 3,100 ft3/s in the GIWW east of HNC at Houma and 2,880 ft3/s east of Bayou Lafourche at Larose. The LAR at Morgan City is 3 ft or more above NAVD88 for about 7 months in a normal year. When the LAR at Morgan City was less than 3 ft above NAVD88, water in the GIWW flowed along the prevailing water-level gradients, to the east between Bay Wallace and the HNC and to the west between WLO and Jaws Bay. However, local runoff and drainage from areas adjacent to the GIWW became more significant in maintaining flow at low LAR stage. Discharge was consistently higher in the GIWW west of the HNC at Houma than farther west near Bay Wallace east of Morgan City, when the LAR at Morgan City was less than 3 ft above NAVD88. Westward flow in the GIWW between Houma and Morgan City was observed near Bay Wallace east of Morgan City but was never observed west of the HNC at Houma. Discharge in the GIWW east of Jaws Bay west of Franklin, La., frequently was higher than in the GIWW west of WLO south of Calumet, La., at low LAR stage. East of the LAR, suspended-sediment concentrations averaged about 162 mg/L (milligrams per liter) at the two sites closest to the LAR, Avoca Island Cutoff Channel and Bayou Penchant south of Morgan Ci

Professional Paper↗

USGS1995

Environmental Setting and Implications on Water Quality, Upper Colorado River Basin, Colorado and Utah

The Upper Colorado River Basin in Colorado and Utah is 1 of 60 study units selected for water-quality assessment as part of the U.S. Geological Survey's National Water-Quality Assessment program, which began full implementation in 1991. Understanding the environmental setting of the Upper Colorado River Basin study unit is important in evaluating water-quality issues in the basin. Natural and human factors that affect water quality in the basin are presented, including an overview of the physiography, climatic conditions, general geology and soils, ecoregions, population, land use, water management and use, hydrologic characteristics, and to the extent possible aquatic biology. These factors have substantial implications on water-quality conditions in the basin. For example, high concentrations of dissolved solids and selenium are present in the natural background water conditions of surface and ground water in parts ofthe basin. In addition, mining, urban, and agricultural land and water uses result in the presence of certain constituents in the surface and ground water of the basin that can detrimentally affect water quality. The environmental setting of the study unit provides a framework of the basin characteristics, which is important in the design of integrated studies of surface water, ground water, and biology.

Water-Resources Investigations Report↗

USGS1996

Using GIS and logistic regression to estimate agricultural chemical concentrations in rivers of the midwestern USA

Agricultural chemicals (herbicides, insecticides, other pesticides and fertilizers) in surface water may constitute a human health risk. Recent research on unregulated rivers in the midwestern USA documents that elevated concentrations of herbicides occur for 1-4 months following application in spring and early summer. In contrast, nitrate concentrations in unregulated rivers are elevated during the fall, winter and spring. Natural and anthropogenic variables of river drainage basins, such as soil permeability, the amount of agricultural chemicals applied or percentage of land planted in corn, affect agricultural chemical concentrations in rivers. Logistic regression (LGR) models are used to investigate relations between various drainage basin variables and the concentration of selected agricultural chemicals in rivers. The method is successful in contributing to the understanding of agricultural chemical concentration in rivers. Overall accuracies of the best LGR models, defined as the number of correct classifications divided by the number of attempted classifications, averaged about 66%.

IAHS-AISH Publication↗

USGS2003

Linking Proxy-Based and Datum-Based Shorelines on a High-Energy Coastline: Implications for Shoreline Change Analyses

A primary purpose of this paper is to quantitatively link variously defined and derived shoreline estimates commonly used for shoreline change analysis. Estimates of shoreline mapping and derivation error, natural shoreline variability, and the relationships between horizontally-derived (proxy-based) shorelines to vertical datums (e.g. MHW) are presented. A series of shoreline repeatability and variability experiments as well as data from a beach monitoring program along the high-energy US Pacific Northwest coast, indicate total uncertainty estimates of the horizontal position of proxy-based shorelines to be approximately ?? 50-150 m for T-sheets and aerial photography and approximately ?? 15 m for datum-based shorelines derived from ground- or air-based topographic surveys. The ability to obtain reliable shoreline change results depends upon both the selected shoreline definition (e.g. horizontal- or feature-based proxy, or datum-based intercept) and the accuracy of the technique used in mapping or interpreting its position. The position of the selected shoreline on the beach profile determines its inherent temporal and spatial variability, an important consideration that has often been overlooked in the scientific literature on shoreline change, Historical shorelines mapped on NOS T-sheets and aerial photos have commonly identified high water line (HWL)-type shorelines, which are shown to be higher on the beach surface than the MHW-datum intercept along coasts subject to wave runup. Analyses of 4.5 years of beach profile data from the southwest Washington coast suggest that both the MHW and HWL-type shorelines have greater natural short-term variability than expected, significantly greater than the variability of shoreline proxies defined farther landward and higher on the beach profile. A model for determining the natural variability of HWL-type shorelines reveals that this short-term variability is the dominant factor in the large total uncertainty values associated with shorelines derived from T-sheets and aerial photographs. The results of these analyses and quantitative comparisons are relevant to determining the significance of historical shoreline changes, as well as to defining the appropriate shoreline proxy or datum and time scale for future shoreline change analysis.

Conference Paper↗

USGS1961

Graphic and algebraic solutions of the discordant lead-uranium age problem

Uranium-bearing minerals that give lead-uranium and lead—lead ages that are essentially in agreement, i.e. concordant, generally are considered to have had a relatively simple geologic history and to have been unaltered since their deposition. The concordant ages obtained on such materials are, therefore, assumed to approach closely the actual age of the minerals. Many uranium-bearing samples, particularly uranium ores, give the following discordant age sequences; Pb 206 U 238 < Pb 207 U 235 ⪡ Pb 207 Pb 206 "> Pb 206 U 238 <Pb 207 U 235 ⪡Pb 207 Pb 206 or, less frequently, Pb 207 Pb 206 ⪡ Pb 207 U 235 < Pb 206 U 238 "> Pb 207 Pb 206 ⪡Pb 207 U 235 <Pb 206 U 238 . These discordant age sequences have been attributed most often to uncertainties in the common lead correction, selective loss of radio-active daughter products, loss or gain of lead or uranium, or contamination by an older generation of radiogenic lead. The evaluation of discordant lead isotope age data may be separated into two operations. The first operation, with which this paper is concerned, is mechanical in nature and involves the calculation of the different possible concordant ages corresponding to the various processes assumed to have produced the discordant ages. The second operation is more difficult to define and requires, in part, some personal judgement. It includes a synthesis of the possible concordant age solutions with other independent geologic and isotopic evidence. The concordant age ultimately chosen as most acceptable should be consistent not only with the known events in the geologic history of the area, the age relations of the enclosing rocks, and the mineralogic and paragenetic evidence, but also with other independent age measurements and the isotopic data obtained on the lead in related or associated non-radioactive minerals. The calculation of the possible concordant ages from discordant age data has been greatly simplified by Wetherill's graphical method of plotting the mole ratios of radiogenic Pb 206 U 238 "> Pb 206 U 238 ( N 206 N 238 "> N 206 N 238 ) vs. radiogenic Pb 207 U 235 "> Pb 207 U 235 ( N 207 N 235 "> N 207 N 235 ) after correcting for the contaminating common Pb 206 and Pb 207 . The linear relationships noted in this graphical procedure have been extended to plots of the mole ratios of total Pb 206 U 238 "> Pb 206 U 238 ( t N 206 N 238 "> t N 206 N 238 ) vs. total Pb 207 U 235 "> Pb 207 U 235 ( t N 207 N 235 "> t N 207 N 235 ). This modification permits the calculation of concordant ages for unaltered samples using only the Pb 207 Pb 206 "> Pb 207 Pb 206 ratio of the contaminating common lead. If isotopic data are available for two samples of the same age, x and y , from the same or related deposits or outcrops, graphs of the normalized difference ratios [ ( N 206 N 204 )x − ( N 206 N 204 )y ( N 238 N 204 )x −( N 238 N 204 )y ] vs. [ ( N 207 N 204 )x − ( N 207 N 204 )y ( N 235 N 204 )x −( N 235 N 204 )y ] "> [(N 206 N 204 )x − (N 206 N 204 )y(N 238 N 204 )x −(N 238 N 204 )y] vs. [(N 207 N 204 )x − (N 207 N 204 )y(N 235 N 204 )x −(N 235 N 204 )y] can give concordant ages corrected for unknown amounts of a common lead with an unknown Pb 207 / Pb 206 ratio. (If thorium is absent the difference ratios may be normalized with the more abundant index isotope, Pb 208 .) Similar plots of tho normalized, difference ratios for three genetically related samples ( x − y ) and( x − z ), will give concordant ages corrected, in addition, for either one unknown period of past alteration or initial contamination by an older generation of radiogenic lead of unknown Pb 207 /Pb 206 ratio. Practical numerical solutions for many of tho concordant age calculations are not currently available. However, the algebraic equivalents of these new graphical methods give equations which may be programmed for computing machines. For geologically probable parameters the equations of higher order have two positive real roots that rapidly converge on the exact concordant ages corrected for original radiogenic lead and for loss or gain of lead or uranium. Modifications of these general age equations expanded only to the second degree have been derived for use with desk calculators. These graphical and algebraic methods clearly suggest both the type and minimum number of samples necessary for adequate mathematical analysis of discordant lead isotope age data. This mathematical treatment also makes it clear that discordant lead isotope data alone cannot provide the basis for the choice of one of the possible concordant age solutions. The new equations, in particular, provide an incentive to improve our physical constants, analytical techniques and sampling methods in order that we may derive all of the useful geologic information that is available in a comprehensive lead isotope age study.

Geochimica et Cosmochimica Acta↗

USGS1995

Lake trout rehabilitation in Lake Erie: a case history

Native lake trout ( Salvelinus namaycush ) once thrived in the deep waters of eastern Lake Erie. The impact of nearly 70 years of unregulated exploitation and over 100 years of progressively severe cultural eutrophication resulted in the elimination of lake trout stocks by 1950. Early attempts to restore lake trout by stocking were unsuccessful in establishing a self-sustaining population. In the early 1980s, New York's Department of Environmental Conservation, Pennsylvania's Fish and Boat Commission, and the U.S. Fish and Wildlife Service entered into a cooperative program to rehabilitate lake trout in the eastern basin of Lake Erie. After 11 years of stocking selected strains of lake trout in U.S. waters, followed by effective sea lamprey control, lake trout appear to be successfully recolonizing their native habitat. Adult stocks have built up significantly and are expanding their range in the lake. Preliminary investigations suggest that lake trout reproductive habitat is still adequate for natural reproduction, but natural recruitment has not been documented. Future assessments will be directed toward evaluation of spawning success and tracking age-class cohorts as they move through the fishery.

Journal of Great Lakes Research↗

USGS2011

Causes and implications of the correlation between forest productivity and tree mortality rates

At global and regional scales, tree mortality rates are positively correlated with forest net primary productivity (NPP). Yet causes of the correlation are unknown, in spite of potentially profound implications for our understanding of environmental controls of forest structure and dynamics and, more generally, our understanding of broad-scale environmental controls of population dynamics and ecosystem processes. Here we seek to shed light on the causes of geographic patterns in tree mortality rates, and we consider some implications of the positive correlation between mortality rates and NPP. To reach these ends, we present seven hypotheses potentially explaining the correlation, develop an approach to help distinguish among the hypotheses, and apply the approach in a case study comparing a tropical and temperate forest. Based on our case study and literature synthesis, we conclude that no single mechanism controls geographic patterns of tree mortality rates. At least four different mechanisms may be at play, with the dominant mechanisms depending on whether the underlying productivity gradients are caused by climate or soil fertility. Two of the mechanisms are consequences of environmental selection for certain combinations of life-history traits, reflecting trade-offs between growth and defense (along edaphic productivity gradients) and between reproduction and persistence (as manifested in the adult tree stature continuum along climatic and edaphic gradients). The remaining two mechanisms are consequences of environmental influences on the nature and strength of ecological interactions: competition (along edaphic gradients) and pressure from plant enemies (along climatic gradients). For only one of these four mechanisms, competition, can high mortality rates be considered to be a relatively direct consequence of high NPP. The remaining mechanisms force us to adopt a different view of causality, in which tree growth rates and probability of mortality can vary with at least a degree of independence along productivity gradients. In many cases, rather than being a direct cause of high mortality rates, NPP may remain high in spite of high mortality rates. The independent influence of plant enemies and other factors helps explain why forest biomass can show little correlation, or even negative correlation, with forest NPP.

Ecological Monographs↗

USGS2009

Geography of Alaska lake districts: Identification, description, and analysis of lake-rich regions of a diverse and dynamic state

Lakes are abundant landforms and important ecosystems in Alaska, but are unevenly distributed on the landscape with expansive lake-poor regions and several lake-rich regions. Such lake-rich areas are termed lake districts and have landscape characteristics that can be considered distinctive in similar respects to mountain ranges. In this report, we explore the nature of lake-rich areas by quantitatively identifying Alaska’s lake districts, describing and comparing their physical characteristics, and analyzing how Alaska lake districts are naturally organized and correspond to climatic and geophysical characteristics, as well as studied and managed by people. We use a digital dataset (National Hydrography Dataset) of lakes greater than 1 hectare, which includes 409,040 individual lakes and represents 3.3 percent of the land-surface area of Alaska. The selection criteria we used to identify lake districts were (1) a lake area (termed limnetic ratio, in percent) greater than the mean for the State, and (2) a lake density (number of lakes per unit area) greater than the mean for the State using a pixel size scaled to the area of interest and number of lakes in the census. Pixels meeting these criteria were grouped and delineated and all groups greater than 1,000 square kilometers were identified as Alaska’s lake districts. These lake districts were described according to lake size-frequency metrics, elevation distributions, geology, climate, and ecoregions to better understand their similarities and differences. We also looked at where lake research and relevant ecological monitoring has occurred in Alaska relative to lake districts and how lake district lands and waters are currently managed. We identified and delineated 20 lake districts in Alaska representing 16 percent of the State, but including 65 percent of lakes and 75 percent of lake area. The largest lake districts identified are the Yukon-Kuskokwim Delta, Arctic Coastal Plain, and Iliamna lake districts with high limnetic ratios of 19, 17, and 21 percent, respectively. The three smallest districts we considered were Tetlin in the eastern interior, Menhiskof on the Alaska Peninsula, and Matanuska–Susitna at the head of Cook Inlet with limnetic ratios of 14, 9, and 9 percent, respectively. Lake density and limnetic ratio were poorly related among lake districts, such that some districts had a few large lakes like Iliamna with Lakes Iliamna and Becharof—the two largest in the State, compared to other districts with many very small lakes like Yukon-Kuskokwim Delta with 111,130 lakes and 63 percent of these less than 10 hectares. Most lake districts are in regions with relatively low precipitation, but temperature regimes varied widely among lake districts. Approximately one-half of lake districts were glaciated during the Pleistocene and similar numbers occur in regions classified as having continuous, discontinuous, and sporadic permafrost, or perennially unfrozen soils. Most districts are at low elevations (less than 250 meters) with two important exceptions being Tetlin with a mean elevation of 530 meters and Ahtna with a mean elevation of 760 meters. These higher elevation districts, particularly Ahtna, had distinct characteristics from other lake districts such as continuous permafrost and Pleistocene glaciation. Several lake districts share similar boundaries to defined ecoregions with lake districts occurring in less than one-half of these 32 ecoregions of Alaska. Most lake districts are lands fully or partly managed by the U.S. Fish and Wildlife Service and the National Park Service, with other land management by the Bureau of Land Management and State and borough government. Much of the U.S. Geological Survey’s lake water-quality sampling efforts has been done in the Arctic Coastal Plain, Matanuska-Susitna, and Iliamna districts but no recorded collections in nine lake districts. Similarly, most lake limnological studies in Alaska were site-specific and represent only a small portion of Alaska’s lake districts. This identification, characterization, and analysis of lake-rich regions may help provide a template to guide future limnological and other scientific research for Alaska.

Alaska↗

USGS2018

The development of a GIS methodology to identify oxbows and former stream meanders from LiDAR-derived digital elevation models

Anthropogenic development of floodplains and alteration to natural hydrological regimes have resulted in extensive loss of off-channel habitat. Interest has grown in restoring these habitats as an effective conservation strategy for numerous aquatic species. This study developed a process to reproducibly identify areas of former stream meanders to assist future off-channel restoration site selections. Three watersheds in Iowa and Minnesota where off-channel restorations are currently being conducted to aid the conservation of the Topeka Shiner ( Notropis topeka ) were selected as the study area. Floodplain depressions were identified with LiDAR-derived digital elevation models, and their morphologic and topographic characteristics were described. Classification tree models were developed to distinguish relic streams and oxbows from other landscape features. All models demonstrated a strong ability to distinguish between target and non-target features with area under the receiver operator curve (AUC) values ≥ 0.82 and correct classification rates ≥ 0.88. Solidity, concavity, and mean height above channel metrics were among the first splits in all trees. To compensate for the noise associated with the final model designation, features were ranked by their conditional probability. The results of this study will provide conservation managers with an improved process to identify candidate restoration sites.

Iowa, Minnesota↗

USGS2016

Recreation, values and stewardship: Rethinking why people engage in environmental behaviors in parks and protected areas

Successfully promoting and encouraging the adoption of environmental stewardship behavior is an important responsibility for public land management agencies. Although people increasingly report high levels of concern about environmental issues, widespread patterns of stewardship behavior have not followed suit (Moore 2002). One concept that can be applied in social science research to explain behavior change is that of values. More specifically, held and assigned values lie at the heart of understanding why people around the world continue to live in unsustainable ways that impact parks and protected areas. A held value is an individual psychological orientation defined by Rokeach as “an enduring belief that a specific mode of conduct or endstate of existence is personally and socially preferable” (1973, 550). Held values are at the core of human cognition, and as such, influence attitudes and behavior. Assigned values on the other hand, according to Brown (1984), are the perceived qualities of an environment that are based on and deduced from held values. In other words, assigned values are considered the material and nonmaterial benefits that people believe they obtain from ecosystems. Held and assigned values predict stewardship behaviors (Figure 1). During the 2013 George Wright Society Conference on Parks, Protected Areas, and Cultural Sites, we organized a session to improve our understanding of why individuals and groups choose to engage in stewardship behaviors that benefit the environment. We used held and assigned values as vehicles to explore what people cared about in diverse landscapes, review select case studies from across the globe, and question how best to incorporate visitor perspectives into protected area management decisions and policymaking. In addition to sharing project results, we also discussed the importance of accounting for multiple and often competing value perspectives, potential ways to integrate disciplinary perspectives on valuing nature, and future directions for social science research and practice. In this paper, we present the results from our session to provide fodder for further contemplation about the timely question of how park and protected area managers can foster values that lead to environmental protection.

Book chapter↗

USGS2021

Tradeoffs in habitat value to maximize natural resource benefits from coastal restoration in a rapidly eroding wetland: Is monitoring land area sufficient?

Louisiana contains nearly 40% of estuarine herbaceous wetlands in the contiguous United States, supporting valuable ecosystem services and providing significant economic benefits to the state and the entire United States. However, coastal Louisiana is a hotspot for rapid land loss from factors including hurricanes, land use change, and high subsidence rates contributing to high relative sea-level rise. The Coastal Protection and Restoration Authority (CPRA) was established after major hurricanes in 2005 to coordinate coastal restoration in Louisiana and develop the Louisiana Coastal Master Plan. The LA Coastal Master Plan uses numerical modeling of multiple scenarios to select a suite of restoration projects based on maximum land area created and flood reduction (as proxies for ecosystem value). Using potential value to aquatic, terrestrial, and social resources, our work compared habitat value of shallow open water areas to emergent wetland. While potential resource benefits varied by emergent wetland salinity type and emergent wetland versus water, they were similar, suggesting that restoration planning based primarily on wetland land area may not achieve the maximum possible ecosystem benefits. After nearly 20 years of integrated restoration planning in coastal Louisiana, a reassessment of restoration planning decision drivers may be beneficial to ensure maximum benefits from coastal restoration. As a result of the Deepwater Horizon oil spill, settlement funds will be a major support to coastal restoration in Louisiana for many years. Assessing potential habitat value to multiple natural and social resources in Louisiana has potential to maximize synergy with large northern Gulf of Mexico restoration programs.

Louisiana↗

USGS1983

[Book review] Waterfowl ecology and management: Selected readings

This book is a compilation of papers from the extensive and varied published literature on the ecology and management of waterfowl. The 125 technical papers reprinted in this book are arranged in eight major sections and are from 21 journals, government reports, several books, and proceedings of symposia and annual conferences. The most frequent sources of papers are The Journal of Wildlife Management, The Auk, Transactions North American Wildlife and Natural Resources Conference, and Wildfowl. These readings span the period from 1937 through 1981. A majority of the technical papers was published during the sixties and seventies, reflecting the expansion of waterfowl research during that period. The front cover and the introductory page of each section are illustrated with black-and-white drawings of North American waterfowl by D. R. Barrick.

The Auk↗