Wind erosion from military training lands in the Mojave Desert, California, U.S.A.   总被引：1，自引：0，他引：1  

Simon J. van Donk  Xuewen Huang  Edward L. Skidmore  Alan B. Anderson  Dick L. Gebhart  Valerie E. Prehoda  Elizabeth M. Kellogg 《Journal of Arid Environments》2003,54(4):687-703

Military training activities reduce vegetation cover, disturb crusts, and degrade soil aggregates, making the land more vulnerable to wind erosion. The objective of this study was to quantify wind erosion rates for typical conditions at the Marine Corps Air Ground Combat Center, Twentynine Palms, CA, U.S.A. Five Big Spring Number Eight (BSNE) sampler stations were installed at each of five sites. Each BSNE station consisted of five BSNE samplers with the lowest sampler at 0·05 m and the highest sampler at 1·0 m above the soil surface. Once a month, sediment was collected from the samplers for analysis. Occurrence of saltating soil aggregates was recorded every hour using Sensits, one at each site. The site with the most erosion had a sediment discharge of 311 kg m⁻¹ over a period of 17 months. Other sites eroded much less because of significant rock cover or the presence of a crust. Hourly sediment discharge was estimated combining hourly Sensit count and monthly sediment discharge measured using BSNE samplers. More simultaneously measured data are needed to better characterize the relationship between these two and reconstruct a detailed time-series of wind erosion. This measured time-series can then be used for comparison with simulation results from process-based wind erosion models such as the Wind Erosion Prediction System (WEPS), once it has been adapted to the unique aspects of military lands.  相似文献   

Flowpath Delineation and Ground Water Age, Allequash Basin, Wisconsin   总被引：4，自引：0，他引：4  

Christine D. Pint  Randall J. Hunt  Mary P. Anderson 《Ground water》2003,41(7):895-902

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Building Web-Based Spatial Information Solutions around Open Specifications and Open Source Software   总被引：9，自引：0，他引：9  

Geoffrey Anderson  Rafael Moreno-Sanchez 《Transactions in GIS》2003,7(4):447-466

Geographic Information Systems (GIS) are moving from isolated, standalone, monolithic, proprietary systems working in a client‐server architecture to smaller web‐based applications and components offering specific geo‐processing functionality and transparently exchanging data among them. Interoperability is at the core of this new web services model. Compliance with Open Specifications (OS) enables interoperability. Web‐GIS software's high costs, complexity and special requirements have prevented many organizations from deploying their data and geo‐processing capabilities over the World Wide Web. There are no‐cost Open Source Software (OSS) alternatives to proprietary software for operating systems, web servers, and Relational Database Management Systems. We tested the potential of the combined use of OS and OSS to create web‐based spatial information solutions. We present in detail the steps taken in creating a prototype system to support land use planning in Mexico with web‐based geo‐processing capabilities currently not present in commercial web‐GIS products. We show that the process is straightforward and accessible to a broad audience of geographic information scientists and developers. We conclude that OS and OSS allow the development of web‐based spatial information solutions that are low‐cost, simple to implement, compatible with existing information technology infrastructure, and have the potential of interoperating with other systems and applications in the future.  相似文献   

A field comparison of indicators of sublethal stress in the salt-marsh grassSpartina patens     

Kern Ewing  Karen L. McKee  Irving A. Mendelssohn 《Estuaries and Coasts》1997,20(1):48-65

There is a need for research into bioindicators of stress in threatened plant communities such as coastal wetlands. Land subsidence, diversion of sediment, and salt-water intrusion produce stresses associated with waterlogging, elevated salinity, and nutrient depletion. Temporal and spatial environmental variation (soil redox potential, interstitial water salinity, pH, ammonium and phosphorus, and cation and trace metal concentrations) was analyzed near Lake de Cade, Louisiana, in a brackish marsh which is a mosaic of healthy plant communities interspersed with areas where wetland loss is occurring. Environmental variation was related to indicators of stress inSpartina patens, which included variables derived from the adenine nucleotide levels in plants, leaf spectral reflectance, leaf proline concentrations, and shoot elongation. In a comparison of burned and unburned sites, streamside and inland marsh, and along a salinity gradient, among-site differences were found in spectral reflectance and adenine-nucleotide-related indicators. Although it was difficult to relate a single causal environmental variable to the response of a specific indicator, spectral reflectance in the visible light range responded to salinity or to elements borne in seawater, and adenine-nucleotide indices were sensitive to nutrient availability. The ability of indicators to detect plant responses changed during the growing season, suggesting that they were responding to the changing importance of different environmental factors. In addition, some reflectance indicator responses occurred along salinity gradients when salinity differences were less than those that were found to have ecologically meaningful effects in greenhouse experiments. A multivariate numerical approach was used to relate environmental variation with indicator responses. We concluded that factors which in combination cause the degradation and loss of Louisiana wetlands produce environmental conditions that are only subtly different from those in vigorously growing marsh communities.  相似文献   

Past imperfect, future tense: Archaeology and development     

Karen D. Vitelli  K. Anne Pyburn 《Natural Resources Research》1997,6(2):71-84

Archaeological sites are valuable nonrenewable resources and they are being destroyed rapidly by modern development projects of all kinds, worldwide. The contextual information in these sites could tell surprising and valuable stories of human behavior over an enormous sweep of time and might contribute to a better future. Archaeologists’ experience of site destruction and their recent efforts to work with local communities toward alternatives to site destruction may offer examples for others concerned with the treatment of nonrenewable resources  相似文献   

Erosion rates of alpine bedrock summit surfaces deduced from in situ Be and Al     

Eric E. Small  Robert S. Anderson  James L. Repka  Robert Finkel 《Earth and Planetary Science Letters》1997,150(3-4):413-425

We have measured the concentration of in situ produced cosmogenic ¹⁰Be and ²⁶Al from bare bedrock surfaces on summit flats in four western U.S. mountain ranges. The maximum mean bare-bedrock erosion rate from these alpine environments is 7.6 ± 3.9 m My⁻¹. Individual measurements vary between 2 and 19 m My⁻¹. These erosion rates are similar to previous cosmogenic radionuclide (CRN) erosion rates measured in other environments, except for those from extremely arid regions. This indicates that bare bedrock is not weathered into transportable material more rapidly in alpine environments than in other environments, even though frost weathering should be intense in these areas. Our CRN-deduced point measurements of bedrock erosion are slower than typical basin-averaged denudation rates ( 50 m My⁻¹). If our measured CRN erosion rates are accurate indicators of the rate at which summit flats are lowered by erosion, then relief in the mountain ranges examined here is probably increasing.

We develop a model of outcrop erosion to investigate the magnitude of errors associated with applying the steady-state erosion model to episodically eroding outcrops. Our simulations show that interpreting measurements with the steady-state erosion model can yield erosion rates which are either greater or less than the actual long-term mean erosion rate. While errors resulting from episodic erosion are potentially greater than both measurement and production rate errors for single samples, the mean value of many steady-state erosion rate measurements provides a much better estimate of the long-term erosion rate.  相似文献   

Vulnerable or Resilient? A Multi-Scale Assessment of Climate Impacts and Vulnerability in Norway   总被引：2，自引：1，他引：2  

Karen O'Brien  Linda Sygna  Jan Erik Haugen 《Climatic change》2004,64(1-2):193-225

This paper explores the issue of climate vulnerability in Norway, an affluent country that is generally considered to be resilient to the impacts of climate change. In presenting a multi-scale assessment of climate change impacts and vulnerability in Norway, we show that the concept of vulnerability depends on the scale of analysis. Both exposure and the distribution of climate sensitive sectors vary greatly across scale. So do the underlying social and economic conditions that influence adaptive capacity. These findings question the common notion that climate change may be beneficial for Norway, and that the country can readily adapt to climate change. As scale differences are brought into consideration, vulnerability emerges within some regions, localities, and social groups. To cope with actual and potential changes in climate and climate variability, it will be necessary to acknowledge climate vulnerabilities at the regional and local levels, and to address them accordingly. This multi-scale assessment of impacts and vulnerability in Norway reinforces the importance of scale in global change research.  相似文献   

To Be or Not to Be…     

Mary P. Anderson 《Ground water》2004,42(1):1-1

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Viruses as potential regulators of regional brown tide blooms caused by the alga,Aureococcus anophagefferens     

Mary Downes Gastrich  Justine A. Leigh-Bell  Christopher J. Gobler  O. Roger Anderson  Steven W. Wilhelm  Martha Bryan 《Estuaries and Coasts》2004,27(1):112-119

Blooms of the brown tide organismAureccoccus anophagefferens have recurred in the coastal bays in New Jersey since 1995 and in the coastal bays of Long Island since 1985. Intracellular viral-like particles (VLPs) were documented during 1999–2000 brown tide blooms in Little Egg Harbor, New Jersey, but it was not determined whether cells were infected during the termination of the bloom. The objective of this study was to determine if VLPs infected and lysed natural populations ofA. anophagefferens in coastal bays of New Jersey and New York in 2002 with the same frequency as in 1999–2000 and especially at the termination of the bloom. Our results confirmed that the highest percentage (37.5%) of VLP-infected cells occurred at the termination of the brown tide bloom in New Jersey in 2002. Intracellular VLPs were present throughout the bloom event. The percentage of visibly infected cells was higher at the beginning of the bloom than during the peak of the bloom. The intracellular VLPs in natural populations ofA. anophagefferens were consistent in size and shape (approximately 140 nm in diameter) and comparable to those in previous studies. Concentrated viral isolates, prepared from waters during brown tide blooms in New York and New Jersey in 2002, infected healthy laboratoryA. anophagefferens cultures in vitro. The viral isolates associated with the highest laboratory viral activity (lysis positive) were concentrated from water samples having the highest viral and bacteria concentrations. The intracellular viruses in these virally infected laboratory cultures ofA. anophagefferens were similar in size and shape to those found in natural populations. The successful isolation of a virus specific toA. anophagefferens from a brown tide bloom in the field, the similarity of ultrastructure of VLPs infecting both natural populations and laboratory infected cultures, and the pattern of VLP infection during bloom activity in combination with the observed high percentage of VLP-infected cells during bloom termination, supports, the hypothesis that viruses may be a major source of mortality for brown tide blooms in regional coastal bays of New Jersey and New York.  相似文献   

Angular dependence of the switching field and implications for gyromagnetic remanent magnetization in three-axis alternating-field demagnetization     

Karen Nørgaard Madsen 《Geophysical Journal International》2004,157(3):1007-1016

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