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At least 595 records · Page 33Linked to original sources
USGS2016

How biological soil crusts became recognized as a functional unit: a selective history

It is surprising that despite the world-wide distribution and general importance of biological soil crusts (biocrusts), scientific recognition and functional analysis of these communities is a relatively young field of science. In this chapter, we sketch the historical lines that led to the recognition of biocrusts as a community with important ecosystem functions. The idea of biocrusts as a functional ecological community has come from two main scientific branches: botany and soil science. For centuries, botanists have long recognized that multiple organisms colonize the soil surface in the open and often dry areas occurring between vascular plants. Much later, after the initial taxonomic and phyto-sociological descriptions were made, soil scientists and agronomists observed that these surface organisms interacted with soils in ways that changed the soil structure. In the 1970’s, research on these communities as ecological units that played an important functional role in drylands began in earnest, and these studies have continued to this day. Here, we trace the history of these studies from the distant past until 1990, when biocrusts became well-known to scientists and the public.

Book chapter↗
USGS2013

Legumes in prairie restoration: evidence for wide cross-nodulation and improved inoculant delivery

Background and aims Prairie restoration aims to create self-sustaining, resilient prairies that ameliorate biodiversity loss and soil deterioration associated with conversion of native grasslands to agriculture. Legumes are a key component of the nitrogen-limited prairie ecosystem. Evidence suggests that lack of suitable rhizobia may explain legume absence from restored prairies. This study explores effects of novel alternative inoculant delivery methods on: (a) prairie legume establishment, (b) soil biological properties, and (c) inoculant strain ability to nodulate the host over time. Methods Alternative inoculation methods for seven legume species were tested in a replicated field experiment. Legume establishment, microbial biomass carbon and nitrogen, and rhizobial inoculant strain recovery were measured over a 3-year period. Results Legume species richness in the second growing season was enhanced by a soil-applied granular clay inoculant, while seed-applied powdered peat inoculation was generally ineffective. When Dalea rhizobia were recovered 3-year after planting, only 2 % from the seed-applied inoculation treatment identified with the inoculant strains, whereas this amount ranged from 53 to 100 % in the other inoculation treatments. Some legumes established unexpectedly effective symbioses with strains not originally intended for them. Conclusions Results provide new insights on inoculation of native legumes, especially when a mix of seeds is involved and the restoration targets harsh environments.

Minnesota↗
USGS2008

Rivers and streams: Ecosystem dynamics and integrating paradigms

Full understanding of running waters requires an ecosystem perspective, which encompasses the physical and chemical setting in interaction with dependent biological communities. Several conceptual models or paradigms of river and stream ecosystems that capture critical components of lotic ecosystems have been developed, including the ‘river continuum concept’, to describe fluxes of matter and energy within the stream or river channel together with exchanges between the channel and its terrestrial setting. A complete ecosystem perspective includes consideration of hierarchical spatial scales in a temporal context. Flow of energy in lotic ecosystems is driven by two alternative energy sources: sunlight regulating in-stream photosynthesis and plant litter derived from the stream-side riparian corridor or floodplain. Energy transfers within the ecosystem pass through micro- and macroproducers (algae and vascular hydrophytes) and micro- and macroconsumers (microorganisms, invertebrates, and vertebrates). Material fluxes encompass the cycling of key nutrients, such as nitrogen and phosphorus, and the transport, storage, and metabolism of dissolved (DOM) and particulate (POM) organic matter (OM). Growth of lotic periphyton (algae and associated microbes, microzoans, and detritus) and coarse (CPOM) and fine (FPOM) particulate organic matter constitute the food resources of nonpredaceous running-water invertebrates (e.g., shredders that consume CPOM and collectors that feed on FPOM and associated microbes of both).

Book chapter↗
USGS1990

Paraquat Hazards to Fish, Wildlife, and Invertebrates: A Synoptic Review

Paraquat (1,1`dimethyl4,4`bipyridinium) are broad-spectrum contact plant killers and herbage desiccants that were introduced commercially during the past 25 years. Today, they rank among the most widely used herbicides globally and are frequently used in combination with other herbicides. The recommended paraquat field application rates for terrestrial weed control usually range between 0.28 and 1.12 kg/ha (0.25 and 1.0 lb/acre), and for aquatic weed control the range is 0.12.0 mg/l. Paraquat in surface soils generally photodecomposes in several weeks, but paraquat in subsurface soils and sediments may remain bound and biologically unavailablefor many years without significant degradation. Paraquat is not significantly accumulated by earthworms and other species of soil invertebrates and is usually excreted rapidly by higher animals; however, delayed toxic effects including death of birds and mammals are common. At concentrations below the recommended application rate, paraquat is embryotoxic to developing eggs of migratory waterfowl and adversely affects sensitive species of freshwater algae and macrophytes, larvae of crustaceans and frog tadpoles and carp. Sensitive species of birds are negatively affected at daily dose rates of 10 mg/kg body weight or when fed diets containing 20 mg/kg ration or drinking water containing 40 mg/l.

Contaminant Hazard Reviews↗
USGS2003

Mathematical modeling relevant to closed artificial ecosystems

The mathematical modeling of ecosystems has contributed much to the understanding of the dynamics of such systems. Ecosystems can include not only the natural variety, but also artificial systems designed and controlled by humans. These can range from agricultural systems and activated sludge plants, down to mesocosms, microcosms, and aquaria, which may have practical or research applications. Some purposes may require the design of systems that are completely closed, as far as material cycling is concerned. In all cases, mathematical modeling can help not only to understand the dynamics of the system, but also to design methods of control to keep the system operating in desired ranges. This paper reviews mathematical modeling relevant to the simulation and control of closed or semi-closed artificial ecosystems designed for biological production and recycling in applications in space. Published by Elsevier Science Ltd on behalf of COSPAR.

Advances in Space Research↗
USGS2002

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

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

California↗
USGS1981

Biological and economic impact of stream alteration in the Virginia Piedmont

A 31 month (September 1974 - March 1977) study was conducted on warmwater streams located in the Roanoke Creek watershed of the Piedmont Region of Virginia. The purpose of the study was to determine the effects of stream channelization on the aquatic/riparian wildlife resource and agricultural land-use patterns associated with the altered streams. Three streams, which were channelized 3, 6, and 10 years prior to initiation of the study, and teo unaltered streams, were selected as representative streams for the study. Recently channelized streams lacked overstory cover but has an abundance of herbaceous and small woody plany cover, Conversely, control streams had significantly larger percentages of trees over 46 m tall. Plant species diversity, foliage height diversity, and evenness diversity increased as age since channelization increased. No major differences in water quality parameters were found for either channelized or control streams, although channelized streams had greater deposits of sand and lesser amount of rock, rubble, and gravel. These changes in substrate composition did not significantly modify actual stream flow rates. Fish species composition and species diversity among channelized and unchannelized streams were only slightly different, with most of the differences probably attributable to strays from adjacent habitats, However, evenness diversity for fish communities was lower in channelized streams. The benthic population showed greater changes than did the fish populations with an increase in Chironominae tolerant of unstable sand substrates in channelized streams. Evenness diversity of benthic populations was also higher and showed more consistency in the control stream than in channelized streams. Evenness diversity of benthic communities in control stream averaged between 0.5 to 0.6 and was quite consistent; whereas, the average in the two youngest channelized streams was 0.3 to 0.4. These data seem to indicate decreased stability of the biota in altered streams. In general, benthic macroinvertabrate and fish community parameters collected from channelized streams located 1200 m below a reservoir were either comparable to, or intermediate between, upstream (unchannelized) and reservoir tailwater values. The shallow surface discharge impoundments associated with channelized streams appeared to have a highly localized impact on the downstream benthic marcoinvertabrate and fish communities. During winter, bird species diversity (BSD) among channelized stream sites was not significantly different. During the breeding season, species richness (number of breeding species) and BSD increased with age since channelization. Breeding bird densities were 6.2 pairs/ha in the most recent (3 yr) channelized site and 13.3 pairs/ha on the control streams. Bird diversity and density, particularly for Parulids (warblers), during the breeding season were reduced significantly by removal of tree and shrub layers along channelized streams. No significant differences were found among study sites for either total number of small mammals or their species diversity indices; although, there was a trend toward increasing diversity as age since channelization increased. Smaller differences in species diversity values for small mammals on channelized sites than for birds suggests that small mammal populations require less time for recovery following channelization than avian communities. When streams are channelized: 1) vegetation should be removed from only one side of the stream, with minimal disturbance of top-soil; followed by plantings of herbaceous and woody vegetation, 2) hedgrow plantings should be maintained between agricultural fields and the stream for bank stabilization, 3) dead snags and large trees should be left for birds, 4) all channelization projects should be designed according to the most recent guidelines recommended by the SCS and other resources agencies. In 1958, the Roanoke County Watershed Work Plan projected annual costs of the structured measures (mainly reservoirs and downstream channelization) to be $79,897 and the average annual monetary benefits to be $111,103. With this favorable benefit/cost ration of 1.4, work began in 1960. In 1970, the annual capital cost was 60,780 and operations/maintenance costs were 10,402, or a total annual project cost of $71, 182. High and low values of annual benefits from agricultural income, water supply, recreation, and non-agricultural flood damage were determined for 1970 and compared to annual project cost. The benefit/cost ratio obtained was between 0.25 and 0.58, considerably lower than the 1.4 estimate of the 1958. work plan. This unsatisfactory ratio for the project was due mainly to the failure of the project to encourage large scale cropping of bottomland area. Future projects should be planned with 1) a greater recognition of constraints on farm operator behavior which affect land use change, 2) conservative projection for land use changes in area where agriculture ids in overall decline, 3) increased use of sensitivity analysis to examine the consequences for project economic justification of alternative land use change projections.

Virginia↗
USGS2016

Biological soil crusts as an organizing principle in drylands

Biological soil crusts (biocrusts) have been present on Earth’s terrestrial surfaces for billions of years. They are a critical part of ecosystem processes in dryland regions, as they cover most of the soil surface and thus mediate almost all inputs and outputs from soils in these areas. There are many intriguing, but understudied, roles these communities may play in drylands. These include their function in nutrient capture and transformation, influence on the movement and distribution of nutrients and water within dryland soils, ability to structure vascular plant communities, role in creating biodiversity hotspots, and the possibility that they can be used as indicators of soil health. There are still many fascinating aspects of these communities that need study, and we hope that this chapter will facilitate such efforts.

Book chapter↗
USGS2013

Using prairie restoration to curtail invasion of Canada thistle: the importance of limiting similarity and seed mix richness

Theory has predicted, and many experimental studies have confirmed, that resident plant species richness is inversely related to invisibility. Likewise, potential invaders that are functionally similar to resident plant species are less likely to invade than are those from different functional groups. Neither of these ideas has been tested in the context of an operational prairie restoration. Here, we tested the hypotheses that within tallgrass prairie restorations (1) as seed mix species richness increased, cover of the invasive perennial forb, Canada thistle (Cirsium arvense) would decline; and (2) guilds (both planted and arising from the seedbank) most similar to Canada thistle would have a larger negative effect on it than less similar guilds. Each hypothesis was tested on six former agricultural fields restored to tallgrass prairie in 2005; all were within the tallgrass prairie biome in Minnesota, USA. A mixed-model with repeated measures (years) in a randomized block (fields) design indicated that seed mix richness had no effect on cover of Canada thistle. Structural equation models assessing effects of cover of each planted and non-planted guild on cover of Canada thistle in 2006, 2007, and 2010 revealed that planted Asteraceae never had a negative effect on Canada thistle. In contrast, planted cool-season grasses and non-Asteraceae forbs, and many non-planted guilds had negative effects on Canada thistle cover. We conclude that early, robust establishment of native species, regardless of guild, is of greater importance in resistance to Canada thistle than is similarity of guilds in new prairie restorations.

Minnesota↗
USGS2015

Geochemistry and occurrence of selenium: An overview

Selenium (Se) is both beneficial and toxic to animals, plants, and humans. Consequently, it is imperative to know its concentration in the environment and to understand the processes controlling its distribution. Determinations of Se concentrations in a variety of materials indicate that Se is widely distributed throughout the environment. The processes responsible for its distribution include volcanic activity, the burning of fossil fuels, the weathering of rocks and soils, groundwater transport, precipitation of minerals, adsorption, chemical or bacterial reduction and oxidation, and metabolic uptake and release by plants and animals. The importance of a particular process in controlling the distribution of Se is intimately linked to the speciation of Se, which is controlled by the pH and redox conditions of the environment. Selenium can exist as selenide (Se 2− ), elemental Se (Se 0 ), selenite (SeO 2− 3 ), and selenate (SeO 2− 4 ). Each oxidation state exhibits different chemical behavior. Selenide and elemental Se occur in acidic, reducing, and organic-rich environments. Metal selenides, Se-sulfides, and elemental Se are insoluble, and therefore biologically unavailable. For the pH and redox conditions of most soil and aquatic environments, SeO 2− 3 and SeO 2− 4 ; should be the dominant forms of Se. Selenite is immobilized by adsorption onto particles, particularly Fe oxyhydroxides. Selenate is highly mobile and biologically available because of the solubility of its salts and its weak adsorption by particles. Microbial action can change the speciation of Se through oxidation or reduction, or through the formation of organic Se compounds.

Book chapter↗
USGS2016

Fluctuating water depths affect American alligator ( Alligator mississippiensis ) body condition in the Everglades, Florida, USA

Successful restoration of wetland ecosystems requires knowledge of wetland hydrologic patterns and an understanding of how those patterns affect wetland plant and animal populations.Within the Everglades, Florida, USA restoration, an applied science strategy including conceptual ecological models linking drivers to indicators is being used to organize current scientific understanding to support restoration efforts. A key driver of the ecosystem affecting the distribution and abundance of organisms is the timing, distribution, and volume of water flows that result in water depth patterns across the landscape. American alligators (Alligator mississippiensis) are one of the ecological indicators being used to assess Everglades restoration because they are a keystone species and integrate biological impacts of hydrological operations through all life stages. Alligator body condition (the relative fatness of an animal) is one of the metrics being used and targets have been set to allow us to track progress. We examined trends in alligator body condition using Fulton’s K over a 15 year period (2000–2014) at seven different wetland areas within the Everglades ecosystem, assessed patterns and trends relative to restoration targets, and related those trends to hydrologic variables. We developed a series of 17 a priori hypotheses that we tested with an information theoretic approach to identify which hydrologic factors affect alligator body condition. Alligator body condition was highest throughout the Everglades during the early 2000s and is approximately 5–10% lower now (2014). Values have varied by year, area, and hydrology. Body condition was positively correlated with range in water depth and fall water depth. Our top model was the “Current” model and included variables that describe current year hydrology (spring depth, fall depth, hydroperiod, range, interaction of range and fall depth, interaction of range and hydroperiod). Across all models, interaction between range and fall water depth was the most important variable (relative weight of 1.0) followed by spring and fall water depths (0.99), range (0.96), hydroperiod (0.95) and interaction between range and hydroperiod (0.95). Our work provides additional evidence that restoring a greater range in annual water depths is important for improvement of alligator body condition and ecosystem function. This information can be incorporated into both planning and operations to assist in reaching Everglades restoration goals.

Florida↗
USGS2019

Case studies in groundwater contaminant fate and transport

A case study of groundwater contamination is a detailed study of a single site contaminated with a chemical or mixture that is known to be a problem at many sites. The goal of case studies is to provide insights into the physical, chemical, and biological processes controlling migration, natural attenuation, or remediation of common groundwater contaminants. Ideally, processes occurring at a case study site are representative of other sites so that knowledge gained from these intensive studies can be applied at thousands of sites where fewer data are available. Several characteristics of case studies contribute to their value. First, they may have tens to hundreds of monitoring wells, compared to fewer than ten wells at some contaminated sites. Second, some case studies continue for many years or even decades, providing insights into temporal progression of slow processes. Third, analytical methods prohibitively expensive for routine use or under development may be tested at case study sites. Finally, the ongoing characterization typical of case study sites builds a foundation of knowledge that facilitates sophisticated experimental design and testing of new methods. This article is divided into sections based on the contaminant type because the chemical and biological processes required for remediation vary for each contaminant. Most importantly, some contaminants can be biodegraded whereas metals and radionuclides cannot be destroyed but can be immobilized or rendered less toxic. The emphasis is on case studies of natural processes that control the fate and transport of contaminants in groundwater rather than on active remediation methods. The principles learned from these studies may form the basis for design of remedial strategies. The organic contaminants are divided into: petroleum hydrocarbons, fuel oxygenates, coal tar and wastes from manufactured gas plants, and chlorinated solvents. The inorganic contaminants covered are metals and radionuclides, arsenic, and nitrate. Case studies of mixed waste plumes from landfills are also described. Experimental sites where contaminants have been introduced into an aquifer as an emplaced source or a controlled release may not meet the above definition of case studies, but some are included because the overall goal is to impart lessons learned from detailed field studies. It is impossible to cover all case studies in this short format. Conversely, focusing on one or two does not convey the breadth of research results in entire range of case studies. Instead, the strategy is to describe the evolution of knowledge for each contaminant class while providing citations of relevant case studies. Much of the progress in understanding of the fate of contaminants in groundwater is based on laboratory studies; thus whenever possible, papers that included both field and laboratory results have been included among the citations. Two topics of growing importance have not been covered. These are the fate of pharmaceuticals in groundwater and discharge of contaminant plumes to surface water. These topics merit coverage in the future as knowledge grows and case studies increase in number.

Environmental Science↗
USGS1995

Seasonal/yearly salinity variations in San Francisco Bay

The ability of resource agencies to manage fish, wildlife and freshwater supplies of San Francisco Bay estuary requires an integrated knowledge of the relations between the biota and their physical environment. A key factor in these relations is the role of salinity in determining both the physical and the biological character of the estuary. The saltiness of the water, and particularly its seasonal and interannual patterns of variability, affects which aquatic species live where within the estuary. Salinity also determines where water can and cannot be diverted for human consumption and irrigated agriculture, and plays a role in determining the capacity of the estuary to cleanse itself of wastes. In short, salinity is a fundamental property of estuarine physics and chemistry that, in turn, determines the biological characteristics of each estuary. Freshwater is a major control on estuarine salinity. Most freshwater supplied to the Bay is from river flow through the Delta, which is primarily runoff from the Sierra Nevada. Most contaminants in San Francisco Bay are from the Sacramento/San Joaquin Valley and the local watershed around the Bay rather than the sea or atmosphere. Land is the primary source of freshwater and freshwater serves as a tracer of land-derived substances such as the trace metals (copper, lead and selenium), pesticides and plant nutrients (nitrate and phosphate). The U.S. Geological Survey is collaborating with other agencies and institutions in studying San Francisco Bay salinity using field observations and numerical simulations to define the physical processes that control salinity. The issues that arise from salinity fluctuations, however, differ in the northern and southern parts of the bay. In North Bay we need to know how salinity responds to freshwater flow through the Sacramento/San Joaquin Delta; this knowledge will benefit water managers who determine how much delta flow is needed a) to protect freshwater supplies for municipal water use and b) modulate salinity for a healthy estuary. In South Bay we need to know where the freshwater comes from (the distant Delta or local streams) to sort out the sources of a) contamination or b) dilution.

California↗
USGS1990

Toxicity of municipal wastewater effluents contaminated by pentachlorophenol in southwest Missouri

Toxicity of effluents from two sewage treatment plants in Joplin, Missouri, was tested using Ceriodaphnia dubia and Pimephales promelas . No test organisms survived in effluents from either plant, in effluents diluted with water from Turkey Creek (the receiving stream), or in water from Turkey Creek. Mortality was complete in all but the most dilute treatments of effluents, in which reconstituted water was used as the diluent. High concentrations of pentachlorophenol (130–970 μg liter −1 ) in effluents and the receiving stream likely caused mortality during the 7-day tests. Detectable concentrations of other phenolic compounds indicated the presence in Turkey Creek of other toxic by-products of pentachlorophenol manufacture. This study demonstrated the utility of biological tests of whole effluents to determine toxicity of wastewater effluents.

Missouri↗
USGS2012

Reconnaissance soil geochemistry at the Riverton Uranium Mill Tailings Remedial Action Site, Fremont County, Wyoming

Soil samples were collected and chemically analyzed from the Riverton Uranium Mill Tailings Remedial Action Site, which lies within the Wind River Indian Reservation in Fremont County, Wyoming. Nineteen soil samples from a depth of 0 to 5 centimeters were collected in August 2011 from the site. The samples were sieved to less than 2 millimeters and analyzed for 44 major and trace elements following a near-total multi-acid extraction. Soil pH was also determined. The geochemical data were compared to a background dataset consisting of 160 soil samples previously collected from the same depth throughout the State of Wyoming as part of another ongoing study by the U.S. Geological Survey. Risk from potentially toxic elements in soil from the site to biologic receptors and humans was estimated by comparing the concentration of these elements with soil screening values established by the U.S. Environmental Protection Agency. All 19 samples exceeded the carcinogenic human health screening level for arsenic in residential soils of 0.39 milligrams per kilogram (mg/kg), which represents a one-in-one-million cancer risk (median arsenic concentration in the study area is 2.7 mg/kg). All 19 samples also exceeded the lead and vanadium screening levels for birds. Eighteen of the 19 samples exceeded the manganese screening level for plants, 13 of the 19 samples exceeded the antimony screening level for mammals, and 10 of 19 samples exceeded the zinc screening level for birds. However, these exceedances are also found in soils at most locations in the Wyoming Statewide soil database, and elevated concentrations alone are not necessarily cause for alarm. Uranium and thorium, two other elements of environmental concern, are elevated in soils at the site as compared to the Wyoming dataset, but no human or ecological soil screening levels have been established for these elements.

Wyoming↗
USGS2017

Assessing the impacts of future climate conditions on the effectiveness of winter cover crops in reducing nitrate loads into the Chesapeake Bay Watershed using SWAT model

Winter cover crops (WCCs) have been widely implemented in the Coastal Plain of the Chesapeake Bay watershed (CBW) due to their high effectiveness at reducing nitrate loads. However, future climate conditions (FCCs) are expected to exacerbate water quality degradation in the CBW by increasing nitrate loads from agriculture. Accordingly, the question remains whether WCCs are sufficient to mitigate increased nutrient loads caused by FCCs. In this study, we assessed the impacts of FCCs on WCC nitrate reduction efficiency on the Coastal Plain of the CBW using Soil and Water Assessment Tool (SWAT) model. Three FCC scenarios (2085 – 2098) were prepared using General Circulation Models (GCMs), considering three Intergovernmnental Panel on Climate Change (IPCC) Special Report on Emissions Scenarios (SRES) greenhouse gas emission scenarios. We also developed six representative WCC implementation scenarios based on the most commonly used planting dates and species of WCCs in this region. Simulation results showed that WCC biomass increased by ~ 58 % under FCC scenarios, due to climate conditions conducive to the WCC growth. Prior to implementing WCCs, annual nitrate loads increased by ~ 43 % under FCC scenarios compared to the baseline scenario (2001 – 2014). When WCCs were planted, annual nitrate loads were substantially reduced by ~ 48 % and WCC nitrate reduction efficiency water ~ 5 % higher under FCC scenarios relative to the baseline. The increase rate of WCC nitrate reduction efficiency varied by FCC scenarios and WCC planting methods. As CO2 concentration was higher and winters were warmer under FCC scenarios, WCCs had greater biomass and therefore showed higher nitrate reduction efficiency. In response to FCC scenarios, the performance of less effective WCC practices (e.g., barley, wheat, and late planting) under the baseline indicated ~ 14 % higher increase rate of nitrate reduction efficiency compared to ones with better effectiveness under the baseline (e.g., rye and early planting), due to warmer temperatures. According to simulation results, WCCs were effective to mitigate nitrate loads accelerated by FCCs and therefore the role of WCCs in mitigating nitrate loads is even more important in the given FCCs.

Chesapeake Bay↗
USGS2003

The Chernobyl Nuclear Power Plant accident: ecotoxicological update

The accident at the Chernobyl, Ukraine, nuclear reactor on 26 April 1986 released large amounts of radiocesium and other radionuclides into the environment, contaminating much of the northern hemisphere, especially Europe. In the vicinity of Chernobyl, at least 30 people died, more than 115,000 others were evacuated, and consumption of milk and other foods was banned because of radiocontamination. At least 14,000 human cancer deaths are expected in Russia, Belarus, and the Ukraine as a direct result of Chernobyl. The most sensitive local ecosystems, as judged by survival, were the soil fauna, pine forest communities, and certain populations of rodents. Elsewhere, fallout from Chernobyl significantly contaminated freshwater and terrestrial ecosystems and flesh and milk of domestic livestock; in many cases, radionuclide concentrations in biological samples exceeded current radiation protection guidelines. Reindeer (Rangifer tarandus) in Scandinavia were among the most seriously afflicted by Chernobyl fallout, probably because their main food during winter (lichens) is an efficient absorber of airborne particles containing radiocesium. Some reindeer calves contaminated with 137Cs from Chernobyl showed 137Cs-dependent decreases in survival and increases in frequency of chromosomal aberrations. Although radiation levels in the biosphere are declining with time, latent effects of initial exposure--including an increased frequency of thyroid and other cancers--are now measurable. The full effect of the Chernobyl nuclear reactor accident on natural resources will probably not be known for at least several decades because of gaps in data on long-term genetic and reproductive effects and on radiocesium cycling and toxicokinetics.

Book chapter↗
USGS1981

Sudden death at the end of the Mesozoic

A paleoecological analysis of the fossil record before and after the Cretaceous/Tertiary boundary indicates that the widespread extinctions and biological stresses around the boundary are best explained in terms of a sudden, significant, but short temperature rise. L. Alvarez and co-authors, having found an enrichment in iridium at the same boundary, postulated that it was associated with the impact of an extraterrestrial body. If this body struck the ocean, the water injected into the atmosphere may have led to a transient increase in the global surface temperature. This temperature pulse may have been primarily responsible for the effects observed in the biosphere. The pattern of extinction of higher plant species suggests that splash down occurred in the northern Pacific-Bering Sea area.

Earth and Planetary Science Letters↗