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211.
Monitoring global change: Comparison of forest cover estimates using remote sensing and inventory approaches 总被引:2,自引:0,他引:2
David P. Turner Greg Koerper Hermann Gucinski Charles Peterson Robert K. Dixon 《Environmental monitoring and assessment》1993,26(2-3):295-305
Satellite-based remote sensing offers great potential for frequent assessment of forest cover over broad spatial scales, however, calibration and validation using ground-based surveys are needed. In this study, forest cover estimates for the United States from a recently developed land surface cover map generated from satellite remote sensing data were compared to state-level inventory data from the U.S. National Resources Planning Act Timber Database. The land cover map was produced at the U.S. Geological Survey EROS Data Center and is based on imagery from the AVHRR sensor (spatial resolution 1.1 km). Vegetation type was classified using the temporal signal in the Normalized Difference Vegetation Index derived from AVHRR data. Comparisons revealed close agreement in the estimate of forest cover for extensively forested states with large polygons of relatively similar vegetation such as Oregon. Larger forest cover differences were observed in other states with some regional patterns in the level of agreement apparent.Comparisons in inventory- and remote sensing-based estimates of current forested area with potential vegetation maps indicated the magnitude of past land use change and the potential for future changes. The remote sensing approach appears to hold promise for conducting surveys of forest cover where inventory data are limited or where rates of vegetation change, due to human or climatic factors, are rapid. 相似文献
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The Science of Nature - 相似文献
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Correlations between flash points and vapor pressures at 25 °C for pure organic compounds were investigated. It was found that classification of organic compounds according to their chemical-structural characteristics (e.g., functional groups) was necessary for the correlation study. Under this classification, linearity seems to be the most appropriate correlation to explain the relationship between the inverse of flash points (°K) and the logarithm of vapor pressures (mm Hg) at 25°C for pure organic compounds. A test study to evaluate the validity of a regression line as an estimation of an unknown flash point from a known vapor pressure was carried out with a data set containing 31 alkanes and aromatics; 55% of the flash points were predicted within ±5°Cand89% were within ±10°C. Within limits of ± 5 to 10°C the procedure is useful but should be improved. 相似文献
220.
Summary In the spring of 1981, Tufts University and the International Union for the Conservation of Nature began teaching the World
Conservation Strategy to environmentalists working at the local level. The fourteen-week course that they offered was the
first of a series of initiatives to increase public awareness of the need for local action toward the solution of global environmental
problems. The success of the first course has encouraged other groups to adapt it to their own social and ecological settings,
but there is a pressing need for even more public education. While several aids to teaching the World Conservation Strategy
are now being developed to give local conservation educators access to the Strategy, the initiative for bringing the World
Conservation Strategy to the public should continue to come from these local leaders.
Frank Thibodeau is an environmental biologist and policy analyst with MA and PhD degrees from Tufts University. He is currently
a Research Associate in the Department of Urban and Environmental Policy at Tufts, preparing a book on the World Conservation
Strategy as a foundation for local environmental initiative under the auspicies of IUCN and the World Wildlife Fund. In addition
to his writing and teaching related to the Strategy, he maintains an active research program examining the development of
national and international strategies for the preservation of genetic diversity.
Hermann H. Field, an urban planner and Fellow of the American Institute of Architects, was director of the Planning Office
of the Tufts-New England Medical Center in downtown Boston for 12 years. In 1972 he initiated and then directed a new graduate
department of Urban and Environmental Policy at Tufts University. Since 1978 he has been Professor Emeritus in Environmental
Planning there. In addition to continued involvement in his department he is active on a range of levels in conservation from
the local to the international, including membership on IUCN's Commission on Environmental Planning. 相似文献