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  • 1
    Electronic Resource
    Electronic Resource
    Elevated CO2 and temperature effects on soil carbon and nitrogen cycling in ryegrass/white clover turves of an Endoaquept soil (1995)
    Springer
    Plant and soil 176 (1995), S. 37-49 
    Details
    ISSN: 1573-5036
    Keywords: C cycling ; climate change ; elevated CO2 ; microbial biomass ; N mineralization ; soil respiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Effects of elevated CO2 (700 μL L−1) and a control (350 μL L−1 CO2) on the productivity of a 3-year-old ryegrass/white clover pasture, and on soil biochemical properties, were investigated with turves of a Typic Endoaquept soil in growth chambers. Temperature treatments corresponding to average winter, spring, and summer conditions in the field were applied consecutively to all of the turves. An additional treatment, at 700 μL L−1 CO2 and a temperature 6°C higher throughout than in the other treatments, was included. Under the same temperature conditions, overall herbage yields in the ‘700 μL L−1 CO2’ treatment were ca. 7% greater than in the control at the end of the ‘summer’ period. Root mass (to ca 25 cm depth) in the ‘700 μL L−1 CO2’ treatment was then about 50% greater than in the control, but in the ‘700 μL L−1 CO2+6°C’ treatment it was 6% lower than in the control. Based on decomposition results, herbage from the ‘700 μL L−1+6°C’ treatment probably contained the highest proportion of readily decomposable components. Elevated CO2 had no consistent effect on soil total C and N, microbial C and N, or extractable C concentrations in any of the treatments. Under the same temperature conditions, it did, however, enhance soil respiration (CO2-C production) and invertase activity. The effects of elevated CO2 on rates of net N mineralization were less distinct, and the apparent availability of N for the sward was not affected. Under elevated CO2, soil in the higher-temperature treatment had a higher microbial C:N ratio; it also had a greater potential to degrade plant materials. Data interpretation was complicated by soil spatial variability and the moderately high background levels of organic matter and biochemical properties that are typical of New Zealand pasture soils. More rapid cycling of C under CO2 enrichment is, nevertheless, indicated. Futher long-term experiments are required to determine the overall effect of elevated CO2 on the soil C balance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00017673
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Elevated CO2 effects on carbon and nitrogen cycling in grass/clover turves of a Psammaquent soil (1996)
    Springer
    Plant and soil 182 (1996), S. 185-198 
    Details
    ISSN: 1573-5036
    Keywords: C cycling ; elevated CO2 ; microbial biomass ; N mineralization ; plant decomposition ; soil respiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Effects of elevated CO2 (525 and 700 μL L−1), and a control (350 μL L−1 CO2), on biochemical properties of a Mollic Psammaquent soil in a well-established pasture of C3 and C4 grasses and clover were investigated with continuously moist turves in growth chambers over four consecutive seasonal temperature regimes from spring to winter inclusive. After a further ‘spring’ period, half of the turves under 350 and 700 μL L−1 were subjected to ‘summer’ drying and were then re-wetted before a further ‘autumn’ period; the remaining turves were kept continuously moist throughout these additional three consecutive ‘seasons’. The continuously moist turves were then pulse-labelled with 14C-CO2 to follow C pathways in the plant/soil system during 35 days. Growth rates of herbage during the first four ‘seasons’ averaged 4.6 g m−2 day−1 under 700 μL L−1 CO2 and were about 10% higher than under the other two treatments. Below-ground net productivity at the end of these ‘seasons’ averaged 465, 800 and 824 g m−2 in the control, 525 and 700 μL L−1 treatments, respectively. in continuously moist soil, elevated CO2 had no overall effects on total, extractable or microbial C and N, or invertase activity, but resulted in increased CO2-C production from soil, and from added herbage during the initial stages of decomposition over 21 days; rates of root decomposition were unaffected. CO2 produced h−1 mg−1 microbial C was about 10% higher in the 700 μL L−1 CO2 treatment than in the other two treatments. Elevated CO2 had no clearly defined effects on N availability, or on the net N mineralization of added herbage. In the labelling experiment, relatively more 14C in the plant/soil system occurred below ground under elevated CO2, with enhanced turnover of 14C also being suggested. Drying increased levels of extractable C and organic-N, but decreased mineral-N concentrations; it had no effect on microbial C, but resulted in lowered microbial N in the control only. In soil that had been previously ‘summer’-dried, CO2 production was again higher, but net N mineralization was lower, under elevated CO2 than in the control after ‘autumn’ pasture growth. Over the trial period of 422 days, elevated CO2 generally appears to have had a greater effect on soil C turnover than on soil C pools in this pasture ecosystem.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00029050
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  • 3
    Electronic Resource
    Electronic Resource
    Assessment of the feasibility of using CCA (copper, chromium and arsenic)-treated and boric acid-treated sawdust as soil amendments (1992)
    Springer
    Plant and soil 142 (1992), S. 249-258 
    Details
    ISSN: 1573-5036
    Keywords: actinomycetes ; arsenic ; boron ; chromium ; copper ; enzymes ; microbial C ; N mineralization ; nematodes ; nitrification ; respiration ; sawdust ; soil pH
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The effects on soil biochemical and biological properties of a soil amended with Cu-, Cr- and As-(CCA)-treated, or boric-treated, sawdust were investigated using soil adjusted to both pH 5 and pH 7. In one experiment, soil samples were analysed before and after a pot trial conducted to assess the effects of these amendments on plant growth and element uptake (Speir et al., 1992). The other experiment was an incubation study conducted without plants and with soil samples taken for analysis after 0, 4, 8 and 14 weeks at 25°C. Amendment with 10% treated sawdust (v/v) increased total soil concentrations of Cu, Cr, As and B by 45, 136, 63 and 32 μg g-1, respectively, in the appropriate treatments. At these levels of soil contamination, there were very few negative effects attributable to the CCA- or boric-sawdust amendments on soil respiration, microbial biomass C, enzyme activities, indices of N mineralization and nitrification, numbers of nematodes, total microbial numbers and numbers of selected actinomycetes. Except for a substantial and significant (p〈0.05) inhibition of sulphatase activity in the boric treatment, the negative effects that did occur were generally small and usually non-significant. These results are discussed and, when considered with those of the plant growth study, warrant a cautious acceptability of CCA-treated sawdust as a mulch or garden amendment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00010970
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  • 4
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    Synthetic aperture radar imaging of ocean waves - Comparison with wave measurements (1980)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: Synthetic aperture radar images of ocean waves were obtained in conjunction with reference wave data near Marineland, Florida, December 14, 1975. Each of the various types of measurements were processed into a form that allowed direct comparisons with the others. Maxima of radar spectra occurred at the same frequencies as the maxima of reference wave height spectra. In a comparison of a radar spectrum with observed spectra of wave height, wave orbital velocity, and surface slope the high-frequency portion of the radar spectrum lay near and between the wave height and the orbital velocity spectra but differed significantly from the surface slope spectrum. The radar-derived mean directions and model-fitted directional spreads of wave energy were close to the values from a directional wave buoy and indicated the accuracy of radar measurements of wave direction. However, a directional plot of a radar spectrum near shore at the frequency of the maximum showed a sharper peak than such a plot of a fitted spectrum derived from reference data.
    Keywords: OCEANOGRAPHY
    Type: Journal of Geophysical Research; 85; Sept. 20
    Format: text
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  • 5
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    Comparison of in situ and remotely sensed ocean waves off Marineland, Florida (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Comparison between X-band and L-band radar imagery of sea waves is made. Sea truth was obtained by in situ pitch-and-roll buoy measurements. Under the low wind and wave conditions of the tests, superior wave imagery and more useful Fourier transforms were obtained with X-band SAR as compared to L-band with equivalent signal-to-noise ratio and synthetic aperture resolution. A comparison between X-band wave images and the in situ measurements shows agreement in the dominant wave direction to within a few degrees. The normalized spectra show a striking resemblance in spectral shape.
    Keywords: OCEANOGRAPHY
    Format: text
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  • 6
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    On the relationship of radar backscatter to wind speed and fetch (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The physics of the interaction of electromagnetic waves with the ocean surface has been an active area of research for a number of years. This paper contains the results of satellite and aircraft experiments to investigate the ability of active microwave radars to infer surface wind speeds remotely. Data obtained from the recent National Aeronautics and Space Administration (NASA) Skylab experiment are compared with surface wind speeds measured by low-flying aircraft and ships-of-opportunity and found to give useful estimates of the ocean wind field. Also investigated was the influence of varying wave height on radar measurements of wind speed by measuring the backscattering cross-section for constant wind speed but variable wave conditions. It is found that this effect is of little importance.
    Keywords: OCEANOGRAPHY
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  • 7
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    Spectral characteristics of the microwave emission from a wind-driven foam-covered sea (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Aircraft observations of the microwave emission from the wind-driven foam-covered Bering Sea substantiate earlier results and show that the combination of surface roughness and white water yields a significant microwave brightness temperature dependence on wind speed over a wide range of microwave wavelengths, with a decreasing dependence for wavelengths above 6 cm. The spectral characteristic of brightness temperature as a function of wind speed is consistent with a foam model in which the bubbles give rise to a cusped surface between the foam and the sea. In the fetch-limited situation the contribution of the wave structure at the surface appears to increase as the foam coverage decreases. Although the data show that the thin streaks are the most important part of the white water signature, there is some evidence for the contribution of whitecaps.
    Keywords: OCEANOGRAPHY
    Type: Journal of Geophysical Research; 81; June 20
    Format: text
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  • 8
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    Spectral variation in the microwave emissivity of the roughened seas (1974)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Recently acquired microwave data obtained from the NASA CV 990 research aircraft have yielded variation of sea surface emissivity as a function of various parameters. Data acquired at a wavelength of 1.5 cm, horizontal polarization, agree with data obtained earlier by Nordberg et al. and Hollinger at nadir and 50 deg viewing angles respectively; the ratio of brightness temperature change to wind speed change was found to be approximately 1 K per meter per second over a wind speed range of 5 to 26 meters per second. Combining these recent measurements with the earlier measurements, it is evident that microwave radiometry can be used as a remote-sensing anemometer over all wind speed ranges of interest. Data analysis revealed that for nadir-viewing instruments, the ratio of brightness temperature change to wind speed change was approximately constant for the 0.8-2.8 cm wavelength range, about three-quarters of that value at 6 cm, and nearly zero at 21 cm. A model is proposed that is consistent with observations.
    Keywords: OCEANOGRAPHY
    Type: Specialist Meeting on Microwave Scattering and Emission from the Earth; Sep 23, 1974 - Sep 26, 1974; Berne; Switzerland
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  • 9
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    Ocean wave detection and direction measurements with microwave radars (1978)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The application of synthetic aperture microwave radar imagery to the measurement of ocean wave direction and wavelength is discussed and an airborne experiment conducted in preparation for the SEASAT-A satellite mission is presented. Models for radar backscattering are examined and it is concluded that the Bragg-Rice model, which represents the ocean surface as a combination of periodic surfaces so that the dominant backscatter matches some portion of the wave spectrum, appears most useful. The experiment was conducted with airborne X-band and L-band synthetic aperture radar (SAR) and data was compared with that obtained from a pitch-and-roll buoy and an instrument package mounted on a sea sled. SAR data was converted to wave spectra and it was found to match data from the buoy, while SAR data on wave direction agrees to within two degrees with the buoy and to within one degree with the sea sled sensors. Wave direction data taken by two real aperture radars is also presented and shown to agree with airborne photographs.
    Keywords: OCEANOGRAPHY
    Type: Oceans ''78: The ocean challenge; Fourth Annual Combined Conference; Sep 06, 1978 - Sep 08, 1978; Washington, DC
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