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   

The age and thermal history of Cerro Rico de Potosi, Bolivia   总被引：1，自引：0，他引：1  

C. G. Cunningham  R. E. Zartman  E. H. McKee  R. O. Rye  C. W. Naeser  O. Sanjinés V  G. E. Ericksen  F. Tavera V 《Mineralium Deposita》1996,31(5):374-385

 Cerro Rico de Potosi, Bolivia, is the world’s largest silver deposit and has been mined since the sixteenth century for silver, and for tin and zinc during the twentieth century, together with by-product copper and lead. The deposit consists primarily of veins that cut an altered igneous body that we interpret to be a dacitic volcanic dome and its underlying tuff ring and explosion breccia. The deposit is compositionally and thermally zoned, having a core of cassiterite, wolframite, bismuthinite, and arsenopyrite surrounded by a peripheral, lower-temperature mineral assemblage consisting principally of sphalerite, galena, lead sulfosalt, and silver minerals. The low-temperature assemblage also was superimposed on the high-temperature assemblage in response to cooling of the main hydrothermal system. Both the dacite dome and the ore fluids were derived from a larger magmatic/hydrothermal source at depth. The dome was repeatedly fractured by recurrent movement on the fault system that guided its initial emplacement. The dome was extruded at 13.8±0.2 Ma (2σ), based on U-Th-Pb dating of zircon. Mineralization and alteration occurred within about 0.3 my of dome emplacement, as indicated by a ⁴⁰Ar/³⁹Ar date of 13.76±0.10 Ma (1σ) for sericite from the pervasive quartz-sericite-pyrite alteration associated with the main-stage, high-temperature, mineralization. The last thermal event able to reset zircon fission tracks occurred no later than 12.5±1.1 Ma (1σ), as indicated by fission-tract dating. Minor sericite, and magmatic-steam alunite veins, were episodically formed around 11 Ma and between 8.3 and 5.7 Ma; the younger episodes occurring at the time of extensional fracturing at Cerro Rico and widespread volcanism in the adjacent Los Frailes volcanic field. None of these younger events appear to be significant thermal/mineralizing events; the exceptionally flat thermal release pattern of ³⁹Ar from sericite and the results of the fission-tract dating of zircon show that none of the younger events was hot enough, and lasted long enough, to cause significant loss of Ar or annealing of zircon fission tracks. U-Th-Pb dating of zircon cores indicates a Precambrian progenitor for some zircons, and REE analyses of dated samples of hydrothermally altered dacite show the presence of a prominent positive Eu anomaly, which constrains interpretations of the origin and evolution of the magmatic/hydrothermal system. Received: 14 October 1995/Accepted: 29 January 1996  相似文献   

Transfer of Taiwanese ideas and technology to The Gambia, West Africa: a viable approach to rural development?   总被引：1，自引：0，他引：1  

Kathleen M Baker  Richard Louis Edmonds 《The Geographical journal》2004,170(3):189-211

The development of Taiwan's agricultural sector contributed significantly to the country's transformation from virtual poverty after World War II to a modern industrial nation. Success resulted from the use of appropriate technologies, developed through an exceptionally close working relationship between government, research and development institutions, extension services and farmers in Taiwan. As part of their overseas development aid programme, the Republic of China on Taiwan has established Technical Missions in those developing countries where it receives political recognition. Among these is The Gambia, West Africa, where one focus of Taiwan's current Technical Mission is the development of women's market gardens. Although the gardens have proved successful, there is doubt as to whether their achievements will be sustained once Taiwan's Technical Mission in The Gambia has ended. Field research in Taiwan and in The Gambia, based largely on participatory techniques, has revealed that the low-tech methods introduced from Taiwan are appropriate for the Gambian environment. However, much depends on whether women participating in the schemes can commit sufficient time and energy to the gardens, as at present this is a limiting factor. The potential of the gardens may also be constrained by a lack of appropriate institutional infrastructure, particularly the scope for profitable disposal of garden produce. A major conclusion of the article is that successful transfer of appropriate technology to The Gambia is likely to be impeded by poorly developed coordination between groups that proved to be key 'players' in the development of agriculture in Taiwan: government, research and development institutions, extension services and producers.  相似文献   

Developing Contradictions: Women's Participation as a Site of Struggle Within an Indian NGO*     

Kathleen O'Reilly 《The Professional geographer》2004,56(2):174-184

Women are being hired in increasing numbers by development projects to facilitate women's participation components. Once employed, however, women often find themselves marginalized within their organizations. In this paper, I find that the women's participation component of an Indian drinking water project has enabled the exclusion of women fieldworkers employed by the project. Drawing on the work of Bakhtin, I show participatory approaches as multiple, partial, and contentious. Moves to thwart women fieldworkers and women's participation give rise to struggles over development geography. Analysis of project records, interviews with staff, and observation of staff activities provide evidence for results.  相似文献   

A revised age of ad 667–699 for the latest major eruption at Rabaul     

Chris O. McKee  Michael G. Baillie  Paula J. Reimer 《Bulletin of Volcanology》2015,77(7):1-7

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Diatom-inferred depth models in 8 Canadian boreal lakes: inferred changes in the benthic:planktonic depth boundary and implications for assessment of past droughts     

Kathleen R. Laird  Melanie V. Kingsbury  C.F. Michael Lewis  Brian F. Cumming 《Quaternary Science Reviews》2011,30(9-10):1201-1217

Assessment of past drought in boreal regions, a region predicted to be strongly affected by climate warming, can provide insights into future availability of water. However, limited instrumental data and paleoclimatic data are available for this assessment. To address this lack of data in the boreal region of northwest Ontario, a regional study of lakes in the Winnipeg River Drainage Basin was initiated. Diatom-inferred (D-I) depth models were developed based on surface samples collected along a depth gradient within 8 small boreal lakes. Weighted-averaging and modern analog approaches provided robust within-lake depth models for each of the study lakes, with bootstrapped r² values ranging from 0.90 to 0.98, and root-mean-squared-errors of prediction (RMSEP) between 1.1 and 2.5 m. Large differences in the estimated depth optima for three representative, but common diatom species across our 8 study lakes suggested that within-lake calibration datasets are more appropriate for inferring past drought based in depth models than a regional multi-lake calibration dataset, and that light and related variables are controlling factors governing the maximum depth of benthic taxa. A down-core application of the D-I depth models on a near-shore core from Meekin Lake, retrieved near the present-day ecotone between the benthic and planktonic diatom assemblages indicated highly similar trends in inferred depth (r = 0.96). The models have significant correlations with other metrics of changes in depth including diatom species richness (r = 0.74–0.78) and evenness (r = 0.76–0.8), thereby allowing a check on the strength and direction of the depth inferences down-core. Near-shore cores located near the benthic:planktonic transition is a sensitive region that can provide estimates of past droughts in lakes where such inferences have been difficult to estimate.  相似文献   

Cross-pressuring conservative Catholics? Effects of Pope Francis’ encyclical on the U.S. public opinion on climate change     

Nan Li  Joseph Hilgard  Dietram A. Scheufele  Kenneth M. Winneg  Kathleen Hall Jamieson 《Climatic change》2016,139(3-4):367-380

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Use of cartographic images by expert and novice field geologists in planning fieldwork routes     

Kathleen M. Baker  Andrew C. Johnson  Caitlin N. Callahan  Heather L. Petcovic 《制图学和地理信息科学》2016,43(2):176-187

Topographic maps and aerial photographs are particularly useful when geoscientists are faced with fieldwork tasks such as selecting paths for observation, establishing sampling schemes, or defining field regions. These types of images are crucial in bedrock geologic mapping, a cognitively complex field-based problem-solving task. Geologic mapping requires the geologist to correctly identify rock types and three-dimensional bedrock structures from often partial or poor-quality outcrop data while navigating through unfamiliar terrain. This paper compares the walked routes of novice to expert geologists working in the field (n = 66) with the results of a route planning and navigation survey of a similar population of geologists (n = 77). Results show clearly that those geologists with previous mapping experience make quick and decisive determinations about field areas from available imagery and maps, regardless of whether they are or not physically present in the field area. Recognition of geologic features enabled experts to form and verbalize a specific plan for travel through a landscape based on those features. Novices were less likely to develop specific travel route plans and were less likely to identify critical landscape cues from aerial photographs.  相似文献   

Post-tsunami recovery in Tamil Nadu,India: combined social and infrastructural outcomes     

Elizabeth Jordan  Amy Javernick-Will  Kathleen Tierney 《Natural Hazards》2016,82(2):1327-1340

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Out of new stocks in 2020: A comment on “Not all fisheries will be collapsed in 2048”     

Rainer Froese  Amanda Stern-Pirlot  Kathleen Kesner-Reyes 《Marine Policy》2009

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