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The design, operation, and testing of a high resolution multispectral video system (HRMVS) is described. The system uses state‐of‐the‐art video technology. It incorporates three black‐and‐white (B & W) visible/near‐infrared (NIR) (0.4–1.1 μm) light sensitive solid‐state cameras equipped with band‐pass filters and provides two kinds of simultaneously synchronized video images: (1) color‐infrared (CIR) composite imagery and (2) its three‐band B & W image components. Only CIR composite imagery is presented here with its B & W components (yellow‐green, red, and NIR bands), but any false color combination can be generated by the encoder. Images are recorded on high resolution (400 horizontal lines) Super (S)‐VHS recorders. An independent solid‐state conventional color (0.4–0.7 μm) camcorder (S‐VHS) was optional to this system. It was set up to acquire imagery at approximately the same field‐of‐view as the three‐camera synchronized system. Examples of imagery of various natural resource characteristics are given. Color‐infrared composite imagery had similar color tonal renditions to that of CIR film. The high resolution multispectral Black & White B & W images showed that some terrain features could be discriminated better in certain bands. For example, the yellow‐green (543–0.552 μm) band was best for distinguishing chlorosis in grain sorghum (Sorghum bicolor Moench), whereas the NIR band was optimum for separating biomass levels in alfalfa (Medicago sativa L.). The color and Black & White B & W multispectral image results showed this system to be a valuable and versatile tool for a variety of remote sensing applications. 相似文献
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Abstract Leafy spurge is a troublesome weed on the northern Great Plains of the United States that chemicals and grazing management have not controlled. Remote sensing and geographic information system (GIS) technology have been used to detect and monitor numerous grassland related problems. The objectives of this study were to use both technologies to map and quantify the extent of leafy spurge within Theodore Roosevelt National Park and to provide information for managing the infestation. Analysis of the data indicated that 702 ha of the 18,680 ha park were infested by leafy spurge; however, leafy spurge populations occurring under dense woody canopies, in deep stream channels, and on steep slopes were not always detected. Infestations were especially dense in the western and southeast portions of the park. Most infestations were restricted to riparian zones and smaller drainage channels. Leafy spurge infestations decreased exponentially as distance from stream channels increased (r2=0.98). The significant association of leafy spurge with drainage channels suggests that the weed might be effectively managed on a watershed sub‐basin level. The joint use of GIS and remote sensing proved to be a powerful combination of tools which provided previously unavailable information about the extent and spatial dynamics of leafy spurge within the park. The results of this study will contribute to the development of a comprehensive leafy spurge management plan for Theodore Roosevelt National Park (South Unit). 相似文献
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Bertha Aguilar Reyes Victoria Mejía Avto Goguitchaichvili Jaime Escobar Germán Bayona Francisco Bautista Juan C. Morales Thomas J. Ihl 《Studia Geophysica et Geodaetica》2013,57(4):741-754
Rock-magnetic investigations of environmental samples, such as soils, dust and leaves, can provide useful information on environmental stress. Aim of this paper is to report on the first magnetic survey carried out on environmental samples from Bogotá, Colombia, which is the fifth most populated city of Latin America. We studied three kinds of samples in order to evaluate their potential as pollution markers: soils, urban dust and leaves of the Sauco (Sambucus nigra) tree. Standard magnetic methods were used to analyze the three groups of samples, with special emphasis on leaves investigated here for the first time for environmental purposes. Samples were collected along two perpendicular transects in an area of the city presumably unpolluted, with two different systems of public transportation. Thermomagnetic curves obtained from soils and atmospheric dust show clearly defined ferrimagnetic phase (probably magnetite) as the main magnetic carrier. Curves of acquisition of isothermal remanent magnetization confirm the ferrimagnetic character of magnetic particles. Frequency-dependent magnetic susceptibility was found between 0 and 10%, suggesting less-important contribution of ultrafine super-paramagnetic magnetite. The apparent contradictory results between soils and the rest of samples may reflect different accumulation period for magnetic particles, being shorter for leaves and urban dust than for soils. 相似文献
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Sediment community metabolism associated with continental shelf hypoxia, Northern Gulf of Mexico 总被引：1，自引：0，他引：1
Gilbert T. Rowe Marta Elizabeth Cruz Kaegi John W. Morse Gregory S. Boland Elva G. Escobar Briones 《Estuaries and Coasts》2002,25(6):1097-1106
Net fluxes of respiratory metabolites (O2, dissolved inorganic carbon (DIC), NH4 +, NO3 ?, and NO2 ?) across the sediment-water interface were measured using in-situ benthic incubation chambers in the area of intermittent seasonal hypoxia associated with the Mississippi River plume. Sulfate reduction was measured in sediments incubated with trace levels of35S-labeled sulfate. Heterotrophic remineralization, measured as nutrient regeneration, sediment community oxygen consumption (SOC), sulfate reduction, or DIC production, varied positively as a function of temperature. SOC was inversely related to oxygen concentration of the bottom water. The DIC fluxes were more than 2 times higher than SOC alone, under hypoxic conditions, suggesting that oxygen uptake alone cannot be used to estimate total community remineralization under conditions of low oxygen concentration in the water column. A carbon budget is constructed that compares sources, stocks, transformations, and sinks of carbon in the top meter of sediment. A comparison of remineralization processes within the sediments implicates sulfate reduction as most important, followed by aerobic respiration and denitrification. Bacteria accounted for more than 90% of the total community biomass, compared to the metazoan invertebrates, due presumably to hypoxic stress. 相似文献
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Escobar Luis E. Romero-Alvarez Daniel Larkin Daniel J. Phelps Nicholas B. D. 《中国海洋湖沼学报》2019,37(3):1037-1041
Often facilitated by human-mediated pathways, aquatic invasive species are a threat to the health and biodiversity of global ecosystems. We present a novel approach incorporating survey data of watercraft movement in a social network analysis to reconstruct potential pathways of aquatic invasive species spread between lakes. As an example, we use the green alga Nitellopsis obtusa, also known as starry stonewort, an aquatic invasive species affecting the Great Lakes region in the United States and Canada. The movement of algal fragments via human-mediated pathways(i.e., watercraft) has been hypothesized as the primary driver of starry stonewort invasion. We used survey data collected at boat ramps during the 2013 and 2014 openwater seasons to describe the flow of watercraft from Lake Koronis, where N. obtusa was first detected in Minnesota, to other lakes in the state. Our results suggest that the risk of N. obtusa expansion is not highly constrained by geographic proximity and management efforts should consider highly connected lakes.Estimating human movement via network analysis may help to explain past and future routes of aquatic invasive species infestation between lakes and can improve evidence-based prevention and control efforts. 相似文献
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Elva G. Escobar-Briones Citlali Díaz Pierre Legendre 《Deep Sea Research Part II: Topical Studies in Oceanography》2008,55(24-26):2627
Studies designed to describe the structure of soft bottom meiobenthic communities have used diverse sorting methods, thus making the comparison of results difficult. This study compared sorting specimens using the manual and centrifuge density gradient sorting methods, for two deep-sea depth zones [continental slope (1630–1860 m) and abyssal plain (3720–3830 m)] in the southwestern Gulf of Mexico. The manual sorting method produced more taxonomic groups and higher abundance and biomass values, compared to the differential density Ludox-centrifuge sorting method. The results obtained from the two sorting methods suggest that distribution patterns of deep-sea meiofaunal samples can be an artefacts of the sorting. 相似文献
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AbstractThe Salar de Atacama is located in the most arid desert in the world. Despite its extreme conditions, it has many ecosystems of high ecological value. The Soncor ecosystem, a sequence of lagoons, is the most important environment of the region as it acts as the centre for the breeding of the Andean Flamingo. This salt flat also contains significant mining deposits and is an important water source for the region. Freshwater and brine—enriched in lithium and potassium—are being pumped from the aquifers near to the Soncor ecosystem, which has so far not been greatly affected by this groundwater extraction. However, there is a potential risk that future anthropogenic effects may disturb this fragile environment. The objective of this study is to determine the origin of the water sources of the Soncor ecosystem so as to adequately manage its water resources. Three hypotheses previously proposed in the technical literature were investigated in order to determine proactive actions to protect this fragile ecosystem. The study utilized classic hydrogeological techniques, such as the construction of stratigraphic profiles, piezometric maps and stream gauging, combined with less-common isotopic techniques, such as the 87Sr/86Sr ratio. The results confirmed the hypothesis that the origins of the water sources are associated with groundwater inputs coming from the east side of the salt flat, in the north of the basin.Editor Z.W. Kundzewicz; Associate editor M. AcremanCitation Ortiz, C., Aravena, R., Briones, E., Suárez, F., Tore, C., and Muñoz, J.F., 2014. Sources of surface water for the Soncor ecosystem, Salar de Atacama basin, northern Chile. Hydrological Sciences Journal, 59 (2), 336–350. 相似文献
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Jaime Escobar Thomas J. Whitmore George D. Kamenov Melanie A. Riedinger-Whitmore 《Journal of Paleolimnology》2013,49(2):237-252
We examined the anthropogenic lead (Pb) burden that accumulated in sediment of lakes in the southeastern USA during the last ~150 years. Mining, smelting, agriculture, and fossil-fuel combustion are known to have contributed to Pb pollution in lakes of other regions. Few studies, however, have examined Pb sequestered in lakes of the southeastern USA, particulary peninsular Florida, which is subject to less continental atmospheric influence than other regions of the eastern USA. We obtained sediment cores from Little Lake Jackson and Little Lake Bonnet in Highlands County, Florida and used Pb isotopes in the records to identify principal sources of Pb contamination. The sediment records showed that changes in Pb concentration and isotope ratios correspond temporally with gasoline consumption in the USA, as well as with changes in lead ores used to produce leaded gasoline. Lead concentrations in the study lakes showed temporal variations that were similar to those found in peat records from east-central Florida. Isotope trends were similar to the mean USA atmospheric Pb deposition record, and to Pb isotope records from Bermuda and Atlantic corals. We modeled the isotopic composition of the anthropogenic Pb in lake sediments and found that the overall trend is controlled by Pb that was released during leaded gasoline combustion. There is, however, additional Pb at each site that comes from sources that are not fully represented by the natural, background Pb. Lead isotope ratios and Pb/arsenic (As) ratios provide evidence that Pb deposition in lakes during the middle 1900s might have been influenced by lead arsenate applications to golf courses, a source that is often ignored in Pb isotope studies. Isotope evidence confirms, however, that following cessation of commercial lead arsenate use in the 1960s, atmospheric alkyl lead was again the primary influence on Pb in sediments of the study lakes. 相似文献
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