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At least 1,189 records · Page 66Linked to original sources
USGS2005

Reach-scale effects of riparian forest cover on urban stream ecosystems

We compared habitat and biota between paired open and forested reaches within five small streams (basin area 10?20 km2) in suburban catchments (9%?49% urban land cover) in the Piedmont of Georgia, USA. Stream reaches with open canopies were narrower than forested reaches (4.1 versus 5.0 m, respectively). There were no differences in habitat diversity (variation in velocity, depth, or bed particle size) between open and forested reaches. However, absence of local forest cover corresponded to decreased large wood and increased algal chlorophyll a standing crop biomass. These differences in basal food resources translated into higher densities of fishes in open (9.0 individuals?m?2) versus forested (4.9 individuals?m?2) reaches, primarily attributed to higher densities of the herbivore Campostoma oligolepis. Densities of terrestrial invertebrate inputs were higher in open reaches; however, trends suggested higher biomass of terrestrial inputs in forested reaches and a corresponding higher density of terrestrial prey consumed by water column feeding fishes. Reach-scale biotic integrity (macroinvertebrates, salamanders, and fishes) was largely unaffected by differences in canopy cover. In urbanizing areas where catchment land cover drives habitat and biotic quality, management practices that rely exclusively on forested riparian areas for stream protection are unlikely to be effective at maintaining ecosystem integrity.

Canadian Journal of Fisheries and Aquatic Sciences↗
USGS2006

Planning for robust reserve networks using uncertainty analysis

Planning land-use for biodiversity conservation frequently involves computer-assisted reserve selection algorithms. Typically such algorithms operate on matrices of species presence?absence in sites, or on species-specific distributions of model predicted probabilities of occurrence in grid cells. There are practically always errors in input data?erroneous species presence?absence data, structural and parametric uncertainty in predictive habitat models, and lack of correspondence between temporal presence and long-run persistence. Despite these uncertainties, typical reserve selection methods proceed as if there is no uncertainty in the data or models. Having two conservation options of apparently equal biological value, one would prefer the option whose value is relatively insensitive to errors in planning inputs. In this work we show how uncertainty analysis for reserve planning can be implemented within a framework of information-gap decision theory, generating reserve designs that are robust to uncertainty. Consideration of uncertainty involves modifications to the typical objective functions used in reserve selection. Search for robust-optimal reserve structures can still be implemented via typical reserve selection optimization techniques, including stepwise heuristics, integer-programming and stochastic global search.

Ecological Modelling↗
USGS2004

Overview: Cross-habitat flux of nutrients and detritus

Ecologists have long known that all ecosystems receive considerable quantities of materials from outside their boundaries (e.g., Elton 1927), and quantifying the magnitude of such fluxes has long been a central tenet of ecosystem ecology (e.g., Odum 1971). Thus, one might think that the consequences of such fluxes for food webs would be well understood. However, food webs have traditionally been viewed as if they were isolated from surrounding habitats, a habit that has been particularly persistent in the modeling of food webs. When fluxes from the outside have been considered, they have largely been restricted to constant inputs directly affecting the base of the food web (e.g., solar energy or nutrients), and usually only such issues as their effects on equilibrium conditions have been considered (e.g., the well-known relationships between nutrient inputs and average densities of various food web members).

Book chapter↗
USGS1989

Sedimentary framework of the southern Maine inner continental shelf: Influence of glaciation and sea-level change

Although the tidally influenced shoreline of Maine is longer than that of virtually any other state, almost no research on its geology has been published. In order to go some way towards remedying this, 1500 km of high-resolution seismic reflection data and 800 km of sidescan sonar imagery have been collected. On the basis of these data and observations made during ten submersible dives, more than 800 bottom samples were collected and evaluated for texture and composition. The understanding of the sedimentary framework of the southern Maine shelf and the processes that maintain it are summarized, and future research directions to evaluate the strategic mineral potential are indicated. In the past 14,000 years, the Maine shelf has experienced a deglaciation and two marine transgressions separated by a regression. The deglaciation was accompanied by the first transgression and deposited till interbedded with up to 40 m of glaciomarine sediment (the Presumpscot Formation) across the shelf. The first transgression culminated about 12,500 yrs B.P., and its landward limit is marked by large glaciomarine deltas 50-100 km landward of the present-day coast. Sea level fell until about 9500 yrs B.P., when shorelines were cut at about the 65 m depth and some large "lowstand deltas" were deposited. Sea level has risen since then and in the general absence of modern river sediment input marine processes have reworked the older sediment. Five shelf environments have been defined in terms of their surficial sediment and stratigraphy. Nearshore ramps are sandy regions extending to about 30 m deep offshore of sandy beaches. These may be reworked lowstand deltas, and possess the thickest bodies of sand in the region. Nearshore basins are mud-filled troughs seaward of coastal areas lacking significant river input. Slumping glaciomarine deposits provide most of the Holocene mud that floors these basins. Rocky zones are extensive areas of exposed rock most common in the 30-50 m depth range. These are areas of high carbonate productivity and provide shell fragments to adjacent areas. The outer basins are muddy regions that begin at the 65 m shoreline and extend beyond the 100 m isobath to the deep Gulf of Maine. Finally, shelf valleys are former stream courses that connect nearshore ramps and basins to the outer basins. These bedrock-framed valleys are filled with sand and mud and are apparently still active conduits for the offshore movement of sediment. The mineralogy of the shelf sediment is complex, and it is not yet clear whether glacial homogenization has obliterated distinctions between river drainage basins and the adjacent shelf. Studies are continuing into northern Maine and analysis of the heavy mineralogy of the shelf sediment utilizing a 2 m Humphrey Spiral to process large grab samples and cores has begun. ?? 1989.

Marine Geology↗
USGS1989

The evolution of thermal structure and water chemistry in Lake Nyos

We collected a time series of physical and chemical data to gain a better understanding of the dynamics of Lake Nyos. Measurements of water and gas chemistry, and temperature made during January, March, and May 1987 are compared to data taken in September 1986 just after the initial CO2 gas release. There is no pattern of change in overall heat content of the lake, although heat input to bottom waters (185-208 m) has occurred at a rate of 1600 mW m-2. This increase in heat content translates to a change from 23.38 to 24.12??C at 200 m and can be explained by geothermal heat flow and addition of thermal spring water. Concentrations of Ca2+, Mg2+, Na+, K+, Fe2+ and alkalinity have increased only in bottom waters. In situ lake processes such as sulfate and iron reduction are unable to account for the changes in alkalinity. Observed chemical changes are consistent with a scenario where slightly thermal soda water is being input to the bottom of the lake. Measurements of pCO2 at depth ranged from 18 to 28% of saturation and exhibited horizontal variability. Overall recharge of CO2 in bottom waters is negligible. Mainly because of increasing ion concentrations in bottom water, total stability of the water column increased 33% from 48,800 J m-2 in September 1986 to 64,700 J m-2 in May 1987. As long as CO2 concentrations remain the same, this level of stability is higher than could be disrupted by common limnologic or meteorologic processes. There is thermal and chemical evidence that a buildup of dissolved iron and CO2 in bottom waters must have preceded the August 1986 gas release. In addition, a survey of all crater lakes in Cameroon indicates that only Lakes Nyos and Monoun contain high concentrations of dissolved iron and CO2. Thus there is a low probability of any other Cameroonian lake releasing a substantial volume of CO2. ?? 1989.

Journal of Volcanology and Geothermal Research↗
USGS1989

West Virginia Geological Survey's role in siting fluidized bed combustion facilities

A project is presented which demonstrates the role of geology in planning and siting a fluidized bed combustion facility. Whenever a project includes natural resource utilization, cooperation between geologists and design engineers will provide an input that could and should save costs, similar to the one stated in our initial premise. Regardless of whether cost reductions stem from a better knowledge of fuel and sorbent availabilities, or a better understanding of the local hydrology, susceptibility to mine-subsidence, or other geologic hazards, the geological survey has a vital role in planning. Input to planning could help the fluidized-bed developer and design-engineer solve some economic questions and stretch the financial resources at their disposal.

Conference Paper↗
USGS1991

Measuring the benefits of GIS use

The key to objectively measuring the benefits of GIS use is to realize that there are two different types of benefits and that different techniques must be used to measure each. Efficiency benefits occur when the same task previously done without the GIS can be done less expensively with the GIS. Effectiveness benefits occur when the GIS allows completion of a task that would not have been done without the GIS. Efficiency benefits can be measured by comparing the variable input costs of performing the application with the GIS to the variable input costs prior to the use of the GIS. Effectiveness benefits depend on the value of the unique GIS output. These benefits can be measured by identifying: (a) how the GIS output is different from the non-GIS output, (b) how this difference affects each user of the GIS output, and (c) the value of each of these effects.

Conference Paper↗
USGS1991

Spatial variability and collector requirements for sampling throughfall volume and chemistry under a mixed-hardwood canopy

Ion concentrations were generally less variable within storms compared with net ion input data. Concentrations and net inputs of some ions were consistently less variable than others; for example, Ca2+, NO3-, and SO42- were less variable than NH4 + and K+. These patterns of variability were consistent in comparisons both within and among storms. The relatively low variability of NO3- and SO42- is probably due to dry deposition of these ions as anthropogenic pollutants, while the low variability of Ca2+ is the result of deposition in windblown soil particles. The high variability of NH4+ and K+ is probably the result of biological processes. Ammonium is strongly retained by the canopy, and K+ is readily leached from it. Retention by, and leaching from, the canopy can induce spatial variability as a result of spatial heterogeneity in the biota. Throughfall volume also displayed low variability within and among events, requiring an average of 11 collectors to estimate the mean within 10% at the 95% confidence level. -from Author

Canadian Journal of Forest Research↗
USGS1993

Influence of long term climate change on net infiltration at Yucca Mountain, Nevada

Net infiltration and recharge at Yucca Mountain, Nevada, a potential site for a high level nuclear waste repository, are determined both by the rock properties and past and future changes in climate. A 1-dimensional model was constructed to represent a borehole being drilled through the unsaturated zone. The rock properties were matched to the lithologies expected to be encountered in the borehole. As current paleoclimate theory assumes that 18O increases with wetter and cooler global climates, a past climate scenario, built on depletion of 18O from ocean sediments was used as a basis for climate change over the past 700,000 years. The climate change was simulated by assigning net infiltration values as a linear function of 8O. Assuming the rock properties, lithologies and climate scenarios are correct, simulations indicated that Yucca Mountain is not in steady state equilibrium at the surface (<75 meters) when compared to measured data, but that the system could be at steady state conditions at depths of >250 meters. Based on the cyclic climate inputs, the near surface is currently in a long term drying trend (for the last 3,000 years) yet recharge into the water table is continuing to occur at an average rate equivalent to the average input rate of the climate model, indicating that conditions at depth are damped out over very long time periods. The Paintbrush Tuff nonwelded units, positioned between the Tiva Canyon and Topopah Spring welded Tuff Members, do not appear to act as capillary barrier and therefore would not perch water. The low porosity vitric caprock and basal vitrophyre of the Topopah Spring Member, however, act as restrictive layers. The higher porosity rock directly above the caprock reduces the potential for the caprock to perch water leaving the basal vitrophyre as the most likely location for perched water to develop.

Conference Paper↗
USGS1996

The influence of landscape position on lake chemical responses to drought in northern Wisconsin

Climatic shifts to drier conditions during drought alter the hydrologic pathways of water and solute flow to aquatic ecosystems. We examined differences in drought-induced trends in the semiconservative cations, Ca+Mg, in seven northern Wisconsin lakes. These spanned the range of hydrologic settings in the region, including hydraulically mounded, groundwater flowthrough, and groundwater-discharge lakes. Parallel increases in concentration across the seven lakes during drought were attributable to evapoconcentration. However, we observed divergent trends for mass, which better reflects altered solute flux by accounting for changes in lake volume. Ca+Mg mass increased in three groundwater-dominated lakes as precipitation inputs were low and groundwater discharging from longer flowpaths became proportionately more important. In contrast, decreases in Ca+Mg mass for two precipitation-dominated lakes reflected diminished inputs of solute-rich groundwater. Landscape position, defined by the spatial position of a lake within a hydrologic flow system, accounted for the divergence in chemical responses to drought.

Limnology and Oceanography↗
USGS1999

Sources of nitrate in water from springs and the Upper Floridan aquifer, Suwannee River basin, Florida

In the Suwannee River basin of northern Florida, nitrate-N concentrations are 1.5 to 20 mg 1-1 in waters of the karstic Upper Floridan aquifer and in springs that discharge into the middle reach of the Suwannee River. During 1996-1997, fertilizers and animal wastes from farming operations in Suwannee County contributed approximately 49% and 45% of the total N input, respectively. Values of ??15N-NO3 in spring waters range from 3.9??? to 5.8???, indicating that nitrate most likely originates from a mixture of inorganic (fertilizers) and organic (animal waste) sources. In Lafayette County, animal wastes from farming operations and fertilizers contributed approximately 53% and 39% of the total N input, respectively, but groundwater near dairy and poultry farms has ??15N-NO3 values of 11.0-12.1???, indicative of an organic source of nitrate. Spring waters that discharge to the Suwannee River from Lafayette County have ??15N-NO3 values of 5.4-8.39???, which are indicative of both organic and inorganic sources. Based on analyses of CFCs, the mean residence time of shallow groundwater and spring water ranges between 8-12 years and 12-25 years, respectively.

IAHS-AISH Publication↗
USGS2005

Phosphorus component in AnnAGNPS

The USDA Annualized Agricultural Non-Point Source Pollution model (AnnAGNPS) has been developed to aid in evaluation of watershed response to agricultural management practices. Previous studies have demonstrated the capability of the model to simulate runoff and sediment, but not phosphorus (P). The main purpose of this article is to evaluate the performance of AnnAGNPS on P simulation using comparisons with measurements from the Deep Hollow watershed of the Mississippi Delta Management Systems Evaluation Area (MDMSEA) project. A sensitivity analysis was performed to identify input parameters whose impact is the greatest on P yields. Sensitivity analysis results indicate that the most sensitive variables of those selected are initial soil P contents, P application rate, and plant P uptake. AnnAGNPS simulations of dissolved P yield do not agree well with observed dissolved P yield (Nash-Sutcliffe coefficient of efficiency of 0.34, R2 of 0.51, and slope of 0.24); however, AnnAGNPS simulations of total P yield agree well with observed total P yield (Nash-Sutcliffe coefficient of efficiency of 0.85, R2 of 0.88, and slope of 0.83). The difference in dissolved P yield may be attributed to limitations in model simulation of P processes. Uncertainties in input parameter selections also affect the model's performance.

Transactions of the American Society of Agricultur↗
USGS2013

Research strategies for addressing uncertainties

There is an immense volume of information pertaining to research needs for addressing climate change uncertainties and resolving key information gaps. Fortunately, multiple independent efforts to establish research priorities have yielded similar results. Input on research needs is being used to craft national scientific priorities and strategies that are being implemented regionally by agencies and organizations. A number of regionally based efforts are already underway to aggregate and synthesize climate-related management needs and research priorities. Landscape Conservation Cooperatives and Climate Science Centers, funded by the Department of the Interior, are conducting strategic syntheses of common resource-management priorities and related science needs across the Southwest, and many of these priorities and needs are related to climate variability and change. The present Assessment includes many examples of the types of research that are needed to address key climate science uncertainties. The Assessment also includes examples of information needs related to understanding climate effects on systems (human, biophysical, ecosystems, and others) in the Southwest. Implementation of research strategies will increase understanding and improve the ability of the scientific community to anticipate the direction or magnitude of future climate-related change in these systems. The assembly of experts for the other chapters of this document provided a unique opportunity to draw upon the authors’ collective expertise to share knowledge about priority research strategies. The peer-reviewed information sources assessed in this chapter highlight research strategies and priorities established by the research community. Other sources cover priorities that are based primarily on management and policy needs. In the latter type, the sources represent the consensus of senior leaders of organizations, generally with substantial input and advice from the organizations’ technical and scientific experts.

Book chapter↗
USGS2012

Assessing future risks to agricultural productivity, water resources and food security: How can remote sensing help?

Although global food production has been rising, the world sti ll faces a major food security challenge. Over one billion people are currently undernourished (Wheeler and Kay, 2010). By the 2050s, the human population is projected to grow to 9.1 billion. Over three-quarters of these people will be living in developing countries, in regions that already lack the capacity to feed their populations . Under current agricultural practices, the increased demand for food would require in excess of one billion hectares of new cropland, nearly equivalent to the land area of the United States, and would lead to significant increases in greenhouse gases (Tillman et al. , 2011). Since climate is the primary determinant of agricultural productivity, changes to it will influence not only crop yields, but also hydrologic balances and supplies of inputs to managed farming systems, and may lead to a shift in the geographic location of some crops . Therefore, not only must crop productivity (yield per unit of land; kg/m 2 ) increase, but water productivity (yield per unit of water or "crop per drop"; kg/m 3 ) must increase as well in order to feed a burgeoning population against a backdrop of changing dietary consumption patterns, a changing climate and the growing scarcity of water and land (Beddington, 2010). The impact from these changes wi ll affect the viability of both dryland subsistence and irrigated commodity food production (Knox, et al. , 2010a). Since climate is a primary determinant of agricultural productivity, any changes will influence not only crop yields, but also the hydrologic balances, and supplies of inputs to managed farming systems as well as potentially shifting the geographic location for specific crops . Unless concerted and collective action is taken, society risks worldwide food shortages, scarcity of water resources and insufficient energy. This has the potential to unleash public unrest, cross-border conflicts and migration as people flee the worst-affected regions to seck refuge in "safe havens", a situation that Beddington described as the "perfect storm" (2010).

Photogrammetric Engineering and Remote Sensing↗
USGS2013

Towards integration of GLAS data into a national fuels mapping program

Comprehensive canopy structure and fuel data are critical for understanding and modeling wildland fire. The LANDFIRE project produces such data nationwide based on a collection of field observations, Landsat imagery, and other geospatial data. Where field data are not available, alternate strategies are being investigated. In this study, vegetation structure data available from GLAS were used to fill this data gap for the Yukon Flats Ecoregion of interior Alaska. The GLAS-derived structure and fuel layers and the original LANDFIRE layers were subsequently used as inputs into a fire behavior model to determine what effect the revised inputs would have on the model outputs. The outputs showed that inclusion of the GLAS data enabled better landscape-level characterization of vegetation structure and therefore enabled a broader wildland fire modeling capability. The results of this work underscore how GLAS data can be incorporated into LANDFIRE canopy structure and fuel mapping.

Alaska↗
USGS1999

Design approaches in quarrying and pit-mining reclamation

Reclaimed mine sites have been evaluated so that the public, industry, and land planners may recognize there are innovative designs available for consideration and use. People tend to see cropland, range, and road cuts as a necessary part of their everyday life, not as disturbed areas despite their high visibility. Mining also generates a disturbed landscape, unfortunately one that many consider waste until reclaimed by human beings. The development of mining provides an economic base and use of a natural resource to improve the quality of human life. Equally important is a sensitivity to the geologic origin and natural pattern of the land. Wisely shaping out environment requires a design plan and product that responds to a site's physiography, ecology, function, artistic form, and publication perception. An examination of selected sites for their landscape design suggested nine approaches for mining reclamation. The oldest design approach around is nature itself. Humans may sometimes do more damage going to an area in the attempt to repair it. Given enough geologic time, a small-site area, and stable adjacent ecosystems, disturbed areas recover without mankind's input. Visual screens and buffer zones conceal the facility in a camouflage approach. Typically, earth berms, fences, and plantings are used to disguise the mining facility. Restoration targets social or economic benefits by reusing the site for public amenities, most often in urban centers with large populations. A mitigation approach attempts to protect the environment and return mined areas to use with scientific input. The reuse of cement, building rubble, macadam meets only about 10% of the demand from aggregate. Recognizing the limited supply of mineral resources and encouraging recycling efforts are steps are steps in a renewable resource approach. An educative design approach effectively communicates mining information through outreach, land stewardship, and community service. Mine sites used for art show a celebration of beauty and experience -- abstract geology. The last design approach combines art and science in a human-nature ecosystem termed integration. With environmental concerns, an operating or reclaimed mine site can no longer be considered isolated from its surroundings. Site analysis of mine works needs to go beyond site-specific information and relate to the regional context of the greater landscape. Understanding design approach can turn undesirable features (mines and pits) into something perceived as desirable by the public.

Book↗
USGS1981

Compressing interpreted satellite imagery for geographic information systems applications over extensive regions

Image processing systems (IPS) and techniques effectively transform satellite imagery into data for input into a spatial database. Geographic information systems (GIS), consisting of graphic input and spatial database management subsystems, are capable of processing digital map and map overlay data to build and manipulate a spatial database. These systems can be successfully integrated to create a successful spatial data handling capability provided certain obstacle are understood and overcome. One of the obstacles faced by all spatial data handling activities involving the extensive regions is the tremendous volume of areal data. Raster formats for representing areal data provide a means of easily integrating IPS and GIS. A compressed raster format has been developed for handling map/image data which greatly reduce the volume of spatial data. By using compressed data strings as basic spatial entities for areal data sets, many complex data processing operations can be simplified. A second set of related problems deals with how this format and other representations of spatial entities, such as vector formats for point and line features, can be interrelated for manipulation, retrieval, and analysis by a spatial database management subsystem. Methods have been developed for interrelating areal data sets in the raster format with point and line data in a vector format and these are described.

Pecora VII Symposium↗
USGS1987

Overview of the land analysis system (LAS)

The Land Analysis System (LAS) is a fully integrated digital analysis system designed to support remote sensing, image processing, and geographic information systems research. LAS is being developed through a cooperative effort between the National Aeronautics and Space Administration Goddard Space Flight Center and the U. S. Geological Survey Earth Resources Observation Systems (EROS) Data Center. LAS has over 275 analysis modules capable to performing input and output, radiometric correction, geometric registration, signal processing, logical operations, data transformation, classification, spatial analysis, nominal filtering, conversion between raster and vector data types, and display manipulation of image and ancillary data. LAS is currently implant using the Transportable Applications Executive (TAE). While TAE was designed primarily to be transportable, it still provides the necessary components for a standard user interface, terminal handling, input and output services, display management, and intersystem communications. With TAE the analyst uses the same interface to the processing modules regardless of the host computer or operating system. LAS was originally implemented at EROS on a Digital Equipment Corporation computer system under the Virtual Memorial System operating system with DeAnza displays and is presently being converted to run on a Gould Power Node and Sun workstation under the Berkeley System Distribution UNIX operating system.

Conference Paper↗