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At least 595 records · Page 33Linked to original sources
USGS2018

Nest tree use by Southern flying squirrels in fragmented midwestern landscapes

Southern flying squirrels ( Glaucomys volans ; SFS) nest in naturally formed cavities in snags and hardwoods found in mature, oak ( Quercus spp.)–hickory ( Carya spp.) forests. Intensive forest fragmentation of the Midwest United States limits the number of available nesting trees. We quantified annual nest‐site selection patterns by southern flying squirrels across fragmented landscapes of west‐central Illinois, USA. We used radiotelemetry to measure nest‐tree use by 55 SFS (30 males, 25 females) captured during 2014–2016. Of 105 nest trees used by SFS, live trees and snags comprised 75% and 25%, respectively. Probability of diurnal nest‐tree use increased 1.08/1.00‐cm increase in diameter‐breast‐height and by 1.50/1‐unit increase in the number of overstory mast trees between random and nest‐tree habitat areas (i.e., 300‐m 2 circular plots). Similarly, probability of diurnal nest‐tree use increased 1.29/1‐unit increase in the number of snags between random and nest‐tree habitat areas. Our results revealed no intersexual differences in patterns of nest‐site selection, which may reflect the tendency for SFS to compensate for reduced availability of key structural attributes (i.e., snags, overstory trees) across fragmented forests by exhibiting similar intersexual patterns of nest‐tree use. Use of natural cavities for denning is encouraging, but also underscores the importance of unharvested oak–hickory forests in contributing essential habitat to SFS populations in fragmented Midwestern landscapes.

Wildlife Society Bulletin↗
USGS2015

Mountain pine beetle host selection between lodgepole and ponderosa pines in the southern Rocky Mountains

Recent evidence of range expansion and host transition by mountain pine beetle ( Dendroctonus ponderosae Hopkins; MPB) has suggested that MPB may not primarily breed in their natal host, but will switch hosts to an alternate tree species. As MPB populations expanded in lodgepole pine forests in the southern Rocky Mountains, we investigated the potential for movement into adjacent ponderosa pine forests. We conducted field and laboratory experiments to evaluate four aspects of MPB population dynamics and host selection behavior in the two hosts: emergence timing, sex ratios, host choice, and reproductive success. We found that peak MPB emergence from both hosts occurred simultaneously between late July and early August, and the sex ratio of emerging beetles did not differ between hosts. In two direct tests of MPB host selection, we identified a strong preference by MPB for ponderosa versus lodgepole pine. At field sites, we captured naturally emerging beetles from both natal hosts in choice arenas containing logs of both species. In the laboratory, we offered sections of bark and phloem from both species to individual insects in bioassays. In both tests, insects infested ponderosa over lodgepole pine at a ratio of almost 2:1, regardless of natal host species. Reproductive success (offspring/female) was similar in colonized logs of both hosts. Overall, our findings suggest that MPB may exhibit equally high rates of infestation and fecundity in an alternate host under favorable conditions.

Rocky Mountains↗
USGS1996

Water Quality in a Wet Meadow, Platte River Valley, Central Nebraska

The Platte River Valley in Nebraska, and in particular the reach from Kearney to Grand Island, is an extremely important natural habitat area. Over 300 migratory bird species, including several threatened and endangered species, have been observed along the Platte River. In the spring, nearly 500,000 sandhill cranes, along with millions of ducks and geese, use this reach as a staging and feeding area during their northerly migration. Wet meadows (grasslands which have waterlogged soils much of the year) are a critical part of this migratory-bird habitat. However, the area of wet meadows between Kearney and Grand Island has declined nearly 50 percent due to the activities of man. The condition of the remaining wet meadows is of vital importance. The U.S. Geological Survey's National Water-Quality Assessment (NAWQA) Program is designed to describe the status and trends in the quality of the Nation's surface water and groundwater resources and to provide a sound understanding of the natural and human factors that affect the quality of these resources. A study of the groundwater beneath a selected wet meadow was undertaken as part of the Central Nebraska Basins NAWQA study unit. Observation wells were installed in the wet meadow at various distances along two transects downgradient from the edge of a corn field. One to five wells completed at depths of about 15 to 100 feet were located at each of the 5 sites. The wells were completed in the Platte River alluvium or the underlying Ogallala Formation. The depth to the water table ranges from 0 to 5 feet below land surface. The general direction of groundwater flow is parallel to flow in the Platte River. Selected wells were sampled in February, March, June, and December 1994 for major cations and anions, nutrients, and organonitrogen herbicides. Pesticides and fertilizers are used extensively in Nebraska to enhance the production of row crops. Some of these pesticides and fertilizers have migrated into the groundwater. Atrazine was detected in water from all of the wells sampled in February and June and most of the wells sampled at other times, but only in concentrations of 0.1 to 0.6 micrograms per liter. Concentrations of the other pesticides analyzed, including alachlor, cyanazine, and metolachlor, were at or below the detection limit of 0.05 micrograms per liter. The highest concentrations of nitrate were found in water from the shallow wells (about 15 feet deep). The concentrations of nitrate as nitrogen in water from these wells ranged from 5 to 13 milligrams per liter in June. Concentrations of major cations and anions decreased and their ratios varied with depth. The major cations were calcium and sodium, and the major anions were sulfate and bicarbonate. Water from the shallowest wells was a mixed calcium sodium sulfate type, whereas the deepest alluvial-aquifer water was a calcium sulfate type. The water from the Ogallala Formation was a calcium bicarbonate type. The variability of the groundwater quality reflects seasonal changes in recharge to and evaporation from the alluvial aquifer and rates of movement and mixing within and between the aquifers.

Fact Sheet↗
USGS2011

Characterizing contaminant concentrations with depth by using the USGS well profiler in Oklahoma, 2003-9

Since 2003, the U.S. Geological Survey (USGS) Oklahoma Water Science Center has been using the USGS well profiler to characterize changes in water contribution and contaminant concentrations with depth in pumping public-supply wells in selected aquifers. The tools and methods associated with the well profiler, which were first developed by the USGS California Water Science Center, have been used to investigate common problems such as saline water intrusion in high-yield irrigation wells and metals contamination in high-yield public-supply wells. The USGS well profiler is a slim (less than 1 inch in diameter), high-pressure hose that can be raised and lowered between the production pipe and casing (or borehole) of a well by using a motorized hose reel. Use of this tool is considerably less expensive than use of standard methods of depth-dependent sampling, and the USGS well profiler generally requires less downtime of the well. In terms of data quality, the greatest advantage of the USGS well profiler is that all data collection is performed under production pumping rates. In Oklahoma, the USGS well profiler has been modified and adapted for use in low-yield (150?350 gallons per minute) wells of various construction types common in Oklahoma. This tool has been used in selected public-supply wells in Hinton, Moore, and Norman to identify which producing zones are contaminated by naturally occurring arsenic. The tool and method also can be used to investigate other nonvolatile contaminants of interest, including uranium, radium, barium, boron, lead, selenium, sulfate, chloride, fluoride, nitrate, and chromium. In 2007, the USGS well profiler was used to investigate saline water intrusion in a deep public-supply well completed in the Ozark (Roubidoux) aquifer. In northeast Oklahoma, where the Ozark aquifer is known to be susceptible to contamination from mining activities, the well profiler also could be used to investigate sources (depths) of metals contamination and to identify routes of entry of metals to production wells.Water suppliers can consider well rehabilitation as a potential remediation strategy because of the ability to identify changes in contaminant concentrations with depth in individual wells with the USGS well profiler. Well rehabilitation methods, which are relatively inexpensive compared to drilling and completing new wells, involve modifying the construction or operation of a well to enhance the production of water from zones with lesser concentrations of a contaminant or to limit the production of water from zones with greater concentrations of a contaminant. One of the most effective well rehabilitation methods is zonal isolation, in which water from contaminated zones is excluded from production through installation of cement plugs or packers. By using relatively simple and inexpensive well rehabilitation methods, water suppliers may be able to decrease exposure of customers to contaminants and avoid costly installation of additional wells, conveyance infrastructure, and treatment technologies.

Fact Sheet↗
USGS1982

Distributed routing rainfall-runoff model; version II

A computer program of a watershed model for routing storm runoff through a branched system of pipes and (or) natural channels using rainfall as input is described. The model provides detailed simulation of storm-runoff periods selected by the user and a daily soil-moisture accounting between storms. A drainage basin is represented as a set of overland-flow, channel, and reservoir seqments which ,jointly describe the drainage features of the basin. Kinematic wave theory is used for routing flows over contributing overland-flow areas and through the channel network. A set of model segments can be arranged into a network that will represent many complex drainage basins. The model is intended primarily for application to urban watersheds, but may have limited applications to rural watersheds.

Open-File Report↗
USGS2009

Channel morphodynamics in four reaches of the Lower Missouri River, 2006-07

Channel morphodynamics in response to flow modifications from Gavins Point Dam are examined in four reaches of the Lower Missouri River. Measures include changes in channel morphology and indicators of sediment transport in four 6 kilometer long reaches located downstream from Gavins Point Dam, near Yankton, South Dakota, Kenslers Bend, Nebraska, Little Sioux, Iowa, and Miami, Missouri. Each of the four reaches was divided into 300 transects with a 20-meter spacing and surveyed during the summer in 2006 and 2007. A subset of 30 transects was randomly selected and surveyed 7-10 times in 2006-07 over a wide range of discharges including managed and natural flow events. Hydroacoustic mapping used a survey-grade echosounder and a Real Time Kinematic Global Positioning System to evaluate channel change. Acoustic Doppler current profiler measurements were used to evaluate bed-sediment velocity. Results indicate varying amounts of deposition, erosion, net change, and sediment transport in the four Lower Missouri River reaches. The Yankton reach was the most stable over monthly and annual time-frames. The Kenslers Bend and Little Sioux reaches exhibited substantial amounts of deposition and erosion, although net change was generally low in both reaches. Total, or gross geomorphic change was greatest in the Kenslers Bend reach. The Miami reach exhibited varying rates of deposition and erosion, and low net change. The Yankton, Kenslers Bend, and Miami reaches experienced net erosion during the time period that bracketed the managed May 2006 spring rise event from Gavins Point Dam.

Scientific Investigations Report↗
USGS2014

Space use and resource selection by foraging Indiana bats at the northern edge of their distribution

Despite 4 decades of conservation concern, managing endangered Indiana bat ( Myotis sodalis ) populations remains a difficult wildlife resource issue facing natural resource managers in the eastern United States. After small signs of population recovery, the recent emergence of white-nose syndrome has led to concerns of local and/or regional extirpation of the species. Where Indiana bats persist, retaining high-quality foraging areas will be critical to meet physiological needs and ensure successful recruitment and overwinter survival. However, insight into foraging behavior has been lacking in the Northeast of the USA. We radio-tracked 12 Indiana bats over 2 summers at Fort Drum, New York, to evaluate factors influencing Indiana bat resource selection during night-time foraging. We found that foraging space use decreased 2% for every 100 m increase in distance to water and 6% for every 100 m away from the forest edge. This suggests high use of riparian areas in close proximity to forest and is somewhat consistent with the species’ foraging ecology in the Midwest and upper South. Given the importance of providing access to high-quality foraging areas during the summer maternity season, Indiana bat conservation at the northern extent of the species’ range will be linked to retention of forested habitat in close proximity to riparian zones.

Endangered Species Research↗
USGS1988

Hydraulic and channel characteristics of selected streams in the Kantishna Hills area, Denali National Park and Preserve, Alaska, 1982-84

The Kantishna Hills area of the Denali National Park and Preserve contains extensive placer gold deposits. In order to develop plans for the management of this natural resource, and to assess the effects of placer mining on aquatic systems, documentation of the physical characteristics of the streams in the area is needed. Channel morphology, streamflow and streambed composition data were collected at 14 stream reaches in the Kantishna Hills area in September 1982 and in June, July, August , and September of 1983 and 1984. The reaches selected include locations of historical and current mining activity and locations which are undisturbed. The data indicate only minor differences in the physical properties of the streams in mined and unmined drainage basins. The composition of streambeds below mined areas tended to consist of finer sized particles and exhibited less variation in mean particle size than streambed in unmined basins. This may be due in part to the natural sorting of material in stream channels because mined areas, and thus study reaches below them, tended to be located relatively farther downstream (nearer the stream mouth) than were study reaches in basins where no mining has occurred. Changes in the physical properties of the streams which could be directly attributed to mining activity were noted at only one location, Rainy Creek near Kantishna, where the stream had been diverted from its natural channel by the construction of settling ponds. (Author 's abstract)

Open-File Report↗
USGS2007

Population response to habitat fragmentation in a stream-dwelling brook trout population

Fragmentation can strongly influence population persistence and expression of life-history strategies in spatially-structured populations. In this study, we directly estimated size-specific dispersal, growth, and survival of stream-dwelling brook trout in a stream network with connected and naturally-isolated tributaries. We used multiple-generation, individual-based data to develop and parameterize a size-class and location-based population projection model, allowing us to test effects of fragmentation on population dynamics at local (i.e., subpopulation) and system-wide (i.e., metapopulation) scales, and to identify demographic rates which influence the persistence of isolated and fragmented populations. In the naturally-isolated tributary, persistence was associated with higher early juvenile survival (-45% greater), shorter generation time (one-half) and strong selection against large body size compared to the open system, resulting in a stage-distribution skewed towards younger, smaller fish. Simulating barriers to upstream migration into two currently-connected tribuory populations caused rapid (2-6 generations) local extinction. These local extinctions in turn increased the likelihood of system-wide extinction, as tributaries could no longer function as population sources. Extinction could be prevented in the open system if sufficient immigrants from downstream areas were available, but the influx of individuals necessary to counteract fragmentation effects was high (7-46% of the total population annually). In the absence of sufficient immigration, a demographic change (higher early survival characteristic of the isolated tributary) was also sufficient to rescue the population from fragmentation, suggesting that the observed differences in size distributions between the naturally-isolated and open system may reflect an evolutionary response to isolation. Combined with strong genetic divergence between the isolated tributary and open system, these results suggest that local adaptation can 'rescue' isolated populations, particularly in one-dimensional stream networks where both natural and anthropegenically-mediated isolation is common. However, whether rescue will occur before extinction depends critically on the race between adaptation and reduced survival in response to fragmentation.

PLoS ONE↗
USGS1978

Map showing principal drainage basins, principal runoff-producing areas, and selected stream flow data in the Kaiparowits coal-basin area, Utah

This is one of a series of maps that describe the geology and related natural resources in the Kaiparowits coal-basin area. Streamflow records used to compile this map and the accompanying table were collected by the U.S. Geological Survey in cooperation with the Utah State Engineer and the Utah Department of Transportation. The principal runoff-producing areas were delineated from a work map (scale 1:250,000) compiled to estimate water yields in Utah (Bagley and others, 1964). Information about Lake Powell was furnished by the U.S. Bureau of Reclamation.

Utah↗
USGS1994

Radionuclides, inorganic constituents, organic compounds, and bacteria in water from selected wells and springs from the southern boundary of the Idaho National Engineering Laboratory to the Hagerman area, Idaho, 1992

Dissolved concentrations of radon-222, a naturally occurring radioactive gas, are found in water in Idaho. The U.S. Geological Survey collected water samples for radon-222 analyses from 339 Idaho wells and springs during 1989-91. These water samples were collected as part of ongoing monitoring programs with the Idaho Department of Water Resources and the U.S. Department of Energy. Concentrations of dissolved radon-222 ranged from -58+30 to 5,715+66 picocuries per liter; the mean and median concentrations were 446+35 and 242+25 picocuries per liter, respectively.

Open-File Report↗
USGS2015

Simulating hydrologic response to climate change scenarios in four selected watersheds of New Hampshire

The State of New Hampshire has initiated a coordinated effort to proactively prepare for the effects of climate change on the natural and human resources of New Hampshire. An important aspect of this effort is to develop a vulnerability assessment of hydrologic response to climate change. The U.S. Geological Survey, in cooperation with the New Hampshire Department of Health and Human Services, is developing tools to predict how projected changes in temperature and precipitation will affect change in the hydrology of watersheds in the State. This study is a test case to assemble the information and create the tools to assess the hydrologic vulnerabilities in four specific watersheds. The study uses output from general circulation models to drive hydrologic simulations of streamflow, groundwater base flow (hereafter referred to as base flow), and snowfall in four representative watersheds in New Hampshire during the 21st century, including the watersheds of the Ashuelot, Oyster, Pemigewasset, and Souhegan Rivers. Simulations show that on average, relative to current conditions, streamflow is likely to increase and base flow is likely to decrease, although this change is highly variable by geographic location and season. Streamflow variability will likely increase, with more high streamflows and more low streamflows. The largest increases in streamflow are in the winter, with small decreases in summer. Change in base flow varies across the State with the largest change in the northern Pemigewasset River watershed. Changes in snowfall are consistently decreasing for all watersheds on average, with the largest change also in the Pemigewasset. However, monthly snowfall totals during any given winter could be higher in the future than expected under current conditions. Increasing frequency of floods (the largest seven floods expected to occur in 20 years) could be more significant than the size of the floods, except in the northern high altitude watersheds. In other words, the projections indicate a pattern of multiple floods that might not breach the riverbanks, yet the increased frequency could put additional strain on the existing river banks, infrastructure, and nearby human settlements. There is also likely to be an increase in high flows during the winter and spring months, which could result in more uncertainty in planning for the design, operation, and maintenance of infrastructure, including roads and utilities. Similarly, it is expected that, on average, there will be less base flow available and a wider range of seasonal fluctuation in base flow than experienced historically. These issues could necessitate more attention to planning and management of the resource. Based on past experience, the most important effects of climate change could be less certain planning options and a greater need for planning that accounts for the effects of larger streamflows than are currently available. The effects of hydrologic change on human health and well-being could be most readily apparent with respect to changes in streamflow and the subsequent increase in the frequency of minor flooding and the frequency of summer and fall low streamflows. These changes could require the development of plans to adapt, protect, and upgrade infrastructure, such as bridges, culverts, roads, and other structures. The precipitation runoff modeling shows that rivers and watersheds in New Hampshire will likely change in response to climate change, and that this response varies with season and latitude. Although four representative areas were simulated in this study, additional models could be used to predict the response over the entire State.

New Hampshire↗
USGS2017

Optimal hydrograph separation using a recursive digital filter constrained by chemical mass balance, with application to selected Chesapeake Bay watersheds

Quantitative estimates of base flow are necessary to address questions concerning the vulnerability and response of the Nation’s water supply to natural and human-induced change in environmental conditions. An objective of the U.S. Geological Survey National Water-Quality Assessment Project is to determine how hydrologic systems are affected by watershed characteristics, including land use, land cover, water use, climate, and natural characteristics (geology, soil type, and topography). An important component of any hydrologic system is base flow, generally described as the part of streamflow that is sustained between precipitation events, fed to stream channels by delayed (usually subsurface) pathways, and more specifically as the volumetric discharge of water, estimated at a measurement site or gage at the watershed scale, which represents groundwater that discharges directly or indirectly to stream reaches and is then routed to the measurement point. Hydrograph separation using a recursive digital filter was applied to 225 sites in the Chesapeake Bay watershed. The recursive digital filter was chosen for the following reasons: it is based in part on the assumption that groundwater acts as a linear reservoir, and so has a physical basis; it has only two adjustable parameters (alpha, obtained directly from recession analysis, and beta, the maximum value of the base-flow index that can be modeled by the filter), which can be determined objectively and with the same physical basis of groundwater reservoir linearity, or that can be optimized by applying a chemical-mass-balance constraint. Base-flow estimates from the recursive digital filter were compared with those from five other hydrograph-separation methods with respect to two metrics: the long-term average fraction of streamflow that is base flow, or base-flow index, and the fraction of days where streamflow is entirely base flow. There was generally good correlation between the methods, with some biased slightly high and some biased slightly low compared to the recursive digital filter. There were notable differences between the days at base flow estimated by the different methods, with the recursive digital filter having a smaller range of values. This was attributed to how the different methods determine cessation of quickflow (the part of streamflow which is not base flow). For 109 Chesapeake Bay watershed sites with available specific conductance data, the parameters of the filter were optimized using a chemical-mass-balance constraint and two different models for the time-dependence of base-flow specific conductance. Sixty-seven models were deemed acceptable and the results compared well with non-optimized results. There are a number of limitations to the optimal hydrograph-separation approach resulting from the assumptions implicit in the conceptual model, the mathematical model, and the approach taken to impose chemical mass balance (including tracer choice). These limitations may be evidenced by poor model results; conversely, poor model fit may provide an indication that two-component separation does not adequately describe the hydrologic system’s runoff response. The results of this study may be used to address a number of questions regarding the role of groundwater in understanding past changes in stream-water quality and forecasting possible future changes, such as the timing and magnitude of land-use and management practice effects on stream and groundwater quality. Ongoing and future modeling efforts may benefit from the estimates of base flow as calibration targets or as a means to filter chemical data to model base-flow loads and trends. Ultimately, base-flow estimation might provide the basis for future work aimed at improving the ability to quantify groundwater discharge, not only at the scale of a gaged watershed, but at the scale of individual reaches as well.

Scientific Investigations Report↗
USGS2020

Water-balance techniques for determining available soil-water storage for selected sandy and clay soil study sites in Cass County, North Dakota, 2016–17

The U.S. Geological Survey, in cooperation with the U.S. Department of Agriculture Natural Resources Conservation Service, collected field and remotely sensed data on precipitation, evapotranspiration (ET), and soil-water content to determine available soil-water storage (AWS) at six study sites on sandy and clay soils in Cass County, North Dakota. Data were collected at all the study sites from May 1–October 31, 2016, and from May 1–October 24, 2017. Estimated daily AWS was determined using daily meteorological and potential evapotranspiration (PET) data obtained from various climate stations, and estimated monthly AWS was determined using monthly meteorological and PET data and monthly ET data determined using the Operational Simplified Surface Energy Balance model. AWS during 2016 and 2017 was determined at daily and monthly time steps because of data availability and to assess results using varying time steps. Comparisons of measured and estimated daily values of AWS at the Brewer Lake site indicated poor agreement during May–October 2016 and May–October 2017. Comparisons of measured and estimated daily values of AWS at the Embden East and Embden West sites indicated poor and fair agreement respectively. At the Lynchburg Crop and Lynchburg Grass sites, comparisons of measured and estimated daily values of AWS indicated fair and good relations, respectively, even with the possible effects of soil cracks. Mean estimated values of daily runoff plus soil percolation for the four sandy soil sites indicated that a maximum of about 19 percent of the estimated runoff plus soil percolation could be considered runoff and that the remaining 81 percent could be considered soil percolation, and for the two clay soil sites about 13 percent of the runoff plus soil percolation could have been considered runoff and about 87 percent could have been considered soil percolation. Results indicated little difference between using monthly PET or monthly ET in water-balance equations to estimate monthly AWS for the grouped sandy soil sites, and only slightly better results were obtained using monthly PET than monthly ET to estimate monthly AWS for the grouped clay soil study sites. Overall, the monthly water-balance models did not perform as well as the daily water-balance models for determining AWS at the six study sites. Additional data collection from a longer-period study and adjustments to the models may improve results from the monthly water-balance techniques.

North Dakota↗
USGS2022

Economical defence of resources structures territorial space use in a cooperative carnivore

Ecologists have long sought to understand space use and mechanisms underlying patterns observed in nature. We developed an optimality landscape and mechanistic territory model to understand mechanisms driving space use and compared model predictions to empirical reality. We demonstrate our approach using grey wolves ( Canis lupus ). In the model, simulated animals selected territories to economically acquire resources by selecting patches with greatest value, accounting for benefits, costs and trade-offs of defending and using space on the optimality landscape. Our approach successfully predicted and explained first- and second-order space use of wolves, including the population's distribution, territories of individual packs, and influences of prey density, competitor density, human-caused mortality risk and seasonality. It accomplished this using simple behavioural rules and limited data to inform the optimality landscape. Results contribute evidence that economical territory selection is a mechanistic bridge between space use and animal distribution on the landscape. This approach and resulting gains in knowledge enable predicting effects of a wide range of environmental conditions, contributing to both basic ecological understanding of natural systems and conservation. We expect this approach will demonstrate applicability across diverse habitats and species, and that its foundation can help continue to advance understanding of spatial behaviour.

Montana↗
USGS2007

Selection for salt tolerance in tidal freshwater swamp species: Advances using baldcypress as a model for restoration: Chapter 14

Worldwide, the intrusion of salinity into irrigated and natural landscapes has major economic and cultural impacts and has resulted in large reductions in crop yields (Epstein et al. 1980; Flowers 2003). Losses have prompted wide-scale programs to improve the salt tolerance of many agronomic species or to identify crop species that can tolerate lands affected by low levels of salinity. Few historic research efforts have considered forest tree species in the United States, especially in nonurban areas. Newer programs have focused on identifying salt tolerance in forest tree species but have mainly limited these efforts to compiling lists of salt tolerant species to be used in afforestation projects (Gogate et al. 1984; Shrivastava et al. 1988; Beckmann 1991; Bell 1999). Gogate et al. (1984), for instance, listed 26 potential species from Australia with silvicultural application to salt affected lands in India. More comprehensive efforts have considered species lists along with specific site requirements (Bell 1999); species tolerant to saline irrigation waters on dry land, for example, will not often be tolerant of salinity increases in wetland settings. Similar ideas have spawned field trials of native and nonnative tree species in India, Pakistan, Thailand, Australia, and the United States (Thomson 1988; Beckmann 1991; Krauss et al. 2000; Conner and Ozalp 2002; Marcar and Crawford 2004; Conner and Inabinette 2005). Concerted attempts at salt tolerance improvement of forest tree species have been limited, owing in part to the diversity of regional issues that such programs must consider. Whereas food, fodder, and pulp yield may be the major improvement goal on salt affected lands in India (Mathur and Sharma 1984), identifying trees that can survive deicing salts (Townsend 1989), oil and gas brine discharges (Auchmoody and Walters 1988), or sea-level rise induced salinity changes (Pezeshki et al. 1987, 1990) are of greater interest to larger industrial nations. Nevertheless, salt tolerance research on a range of tree species has converged on one very important finding; among the mechanisms proposed for salt tolerance in nonhalophytes (Greenway and Munns 1980; Munns and Termaat 1986; Cheeseman 1988), ion exclusion from cellular processes, especially exclusion of Cl- , ranks high (Townsend 1989). Identifying the principal mechanism and location of ion exclusion and determining the range of additive genetic variation available among physiological, morphological, and growth attributes for individual species have been the major elements of salt tolerance improvement programs for trees (Allen et al. 1994a).

Book chapter↗
USGS1991

Effects of lead shot ingestion on selected cells of the mallard immune system

The immunologic effects of lead were measured in game-farm mallards (Anas platyrhynchos) that ingested lead shot while foraging naturally, mallards intubated with lead shot, and unexposed controls. Circulating white blood cells (WBC) declined significantly in male mallards exposed to lead by either natural ingestion or intubation, but not females. Spleen plaque-forming cell (SPFC) counts were significantly lower in mallards intubated with lead pellets compared to controls. Declines in WBC and SPFC means with increasing tissue lead concentrations provide further evidence that lead exposure reduced immunologic cell numbers. Hormonal activity and diet may have influenced the immunologic effects of lead exposure in this study.

Journal of Wildlife Diseases↗
USGS1974

Occurrence of dissolved organic carbon in selected ground-water samples in the United States

A study of nonvolatile DOC (dissolved organic carbon) in ground water was conducted to establish base levels of naturally occurring dissolved organic materials. Samples of ground water were obtained at 100 sites in 27 States. Samples were pressure filtered at the time of collection and immediately frozen on dry ice. DOC concentrations were determined by wet oxidation of organic carbon to carbon dioxide which was measured by an infrared analyzer. The DOC concentrations ranged from less than the 0.1 mg/l limit of detection to 15 mg/l. Concentrations of DOC were directly correlated with specific conductance and alkalinity, but did not correlate with pH. The DOC mean concentration was 1.2 mg/l; however, the DOC median value was lower at 0.7 mg/l. Differences in DOC concentration for various types of consolidated rock aquifers were slight; for example, median DOC values for sandstone, limestone, and crystalline rock aquifer types ranged from 0.5 to 0.7 mg/l. No difference was found in the median DOC concentration between shallow (<200 ft; 61 m) and deep (>200 ft) sand and gravel aquifers.

Journal of Research of the U.S. Geological Survey↗