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  • 1
    Electronic Resource
    Electronic Resource
    Bradford, West Yorkshire : Emerald
    Management of environmental quality 14 (2003), S. 22-38 
    ISSN: 1477-7835
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Economics
    Notes: Year-to-year fluctuations of rainfall in the northern Negev desert provide an opportunity to characterize and assess the temporal dynamics of desertification, phenology, and drought processes. Such information was retrieved and analyzed by combined use of satellite imageries in the reflectivity and thermal spectral bands. Data covering four years of coarse spatial resolution and images from a high revisit time satellite, namely the NOAA-14, were used. The images were processed to produce the normalized difference vegetation index (NDVI) and the land surface temperature (LST). These measures were applied to the sand field in the northwestern Negev (Israel), which is almost totally covered by biological soil crusts, and to an adjacent region in Sinai (Egypt), consisting mainly of bare dune sands. Various manipulations of the data were applied. Time series presentation of the NDVI and LST reveals that the NDVI values correspond to the reaction of the vegetation to rainfall and that LST values represent seasonal climatic fluctuation. Scatterplot analysis of LST vs NDVI demonstrates the following: the two different biomes (Sinai and the Negev) exhibit different yearly variation of the phenological patterns (two seasons in Sinai moving along the LST axis, and three seasons in the Negev, where the NDVI axis represents the growing season); the Sinai has an ecosystem similar to that found in the Sahara, while the Negev, only a few kilometers away, has an ecosystem similar to the one found in the Sahel; and drought indicators were derived by using several geometrical expressions based on the two extreme points of the LST-NDVI scatterplot. The later analysis led to a discrimination function that aims to distinguish between the drought years and the wet years in both biomes. Results from the current study show that a great deal of information on dryland ecosystems can be derived from four, out of five, NOAA/AVHRR spectral bands. The NDVI is derived from the red and the near-infrared bands and the LST from the two thermal bands. Combined use of these two products provides more information than any product alone.
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  • 2
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: To determine the environmental impact of oil-combustion pollutants and soil dust on a lichen, we examined the spectral reflectance of thalli of the epiphytic fruticose lichen, Ramalina duriaei, expressed as values of NDVI (the normalized difference vegetation index). We analyzed electrolyte leakage caused by degradation of cell membranes in terms of electric conductivity of water, apart from chlorophyll degradation, the latter expressed as changes in the A435 nm/A415 nm ratio to indicate the physiological status of the lichen. The concentrations of Al, Cr, Fe, K, Ni, P, sulfate-S, Ti and V in the lichen thallus were measured to quantify the degree of pollution. Thalli of R. duriaei, growing in a nature reserve on the periphery of a 40-year-old industrial town, Ashdod, in southwest Israel were compared with thalli of R. duriaei from an unpolluted forest in the northeastern part of the country transplanted to the polluted areas in and around the town. After an exposure for 10 months, many transplants exhibited lower NDVI values, higher electric conductivity values as well as a lower A435 nm/A415 nm ratio. The three physical/physiological parameters thus reflected severe injury in the lichen transplants. The concentrations of Al, Cr, Fe, Ni, sulfate-S, Ti and V in the lichen transplants were found to correlate inversely with the NDVI values, whereas the concentrations of Fe, Ni, Ti and V were found to correlate with electric conductivity. The decrease in the A435 nm/A415 nm ratio was found to correlate with high concentrations of Al, Fe, Ni, sulfate-S, Ti and V in the lichen transplants, whereas the concentration of K and P correlated with both the NDVI value and the A435 nm/A415 nm ratio. It is concluded that in situ thalli of R. duriaei, the only indigenous fruticose lichen growing in the region of Ashdod, are endangered by the presence of pollutants and by acid rain due to the combustion of heavy fuel oil.
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