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11.
12.
Twenty fertilization experiments were set up in 1985 and 1986 in the Vosges mountains, using mostly calcareous or Mg fertilizers,
in order to verify whether fertilization can attenuate defoliation and yellowing recently recorded in Silver fir and Norway
spruce. In the Ardennes, a fertilization experiment set up in Norway spruce stands prior to the appearance of yellowing was
assessed. In these areas, the total acid deposition is about 2 kg eq H+ ha−1 yr−1. Nitrogen deposition is much more important in the Ardennes (52 kg N ha−1 yr−1 in form of wet and dry deposition) than in the Vosges (16 kg N ha−1 yr−1). The results in the eight adult stands showed no uniform reaction to the treatments. Spontaneous improvement, further deterioration
independently of the treatment, as well as a positive reaction to fertilization were observed. Additional N or P fertilization
sometimes had a beneficial effect on Ca or Mg treatments. The selection of the stands with the best response turns out to
be difficult, as the nutrient contents of needles alone seem not to be a satisfactory criterion for selection. Young plantations
reacted positivley to the treatments. Soluble Mg fertilizer leads to an immediate response. Low solubility Ca-Mg fertilizers
(Ca-Mg lime) did not produce reactions until three years after the application. In the Ardennes, in a 40 yr old spruce stand
suffering from severe Mg deficiency, a Ca and Ca-phosphate fertilization applied 5 yr before yellowing appeared had positive
effects on crown density, discoloration and wood production. Conversely, a single N fertilization in this experiment, as well
as in a young plantation in the Vosges, had a marked negative effect on Mg nutrition, even at low levels. 相似文献
13.
14.
Nanominerals, mineral nanoparticles, and Earth systems 总被引:4,自引:0,他引:4
Hochella MF Lower SK Maurice PA Penn RL Sahai N Sparks DL Twining BS 《Science (New York, N.Y.)》2008,319(5870):1631-1635
Minerals are more complex than previously thought because of the discovery that their chemical properties vary as a function of particle size when smaller, in at least one dimension, than a few nanometers, to perhaps as much as several tens of nanometers. These variations are most likely due, at least in part, to differences in surface and near-surface atomic structure, as well as crystal shape and surface topography as a function of size in this smallest of size regimes. It has now been established that these variations may make a difference in important geochemical and biogeochemical reactions and kinetics. This recognition is broadening and enriching our view of how minerals influence the hydrosphere, pedosphere, biosphere, and atmosphere. 相似文献
15.
We observed directional dynamics in the photodissociation of an oriented molecule. When a laser dissociated hexapole-oriented carbonyl sulfide molecules, the three-dimensional recoil of carbon monoxide fragments, which we measured with ion imaging, was strongly asymmetric. We obtained a microscopic view of molecular bond breaking that revealed both the sign and the magnitude of the deflection angle of the fragment in the molecular frame. This experimental approach can be applied to study and control the three-dimensional dynamics of photoinitiated reactions of fixed molecules or molecules oriented by emerging techniques. 相似文献
16.
Feng L Ayache M Huang J Xu YL Lu MH Chen YF Fainman Y Scherer A 《Science (New York, N.Y.)》2011,333(6043):729-733
Optical communications and computing require on-chip nonreciprocal light propagation to isolate and stabilize different chip-scale optical components. We have designed and fabricated a metallic-silicon waveguide system in which the optical potential is modulated along the length of the waveguide such that nonreciprocal light propagation is obtained on a silicon photonic chip. Nonreciprocal light transport and one-way photonic mode conversion are demonstrated at the wavelength of 1.55 micrometers in both simulations and experiments. Our system is compatible with conventional complementary metal-oxide-semiconductor processing, providing a way to chip-scale optical isolators for optical communications and computing. 相似文献
17.
Frank van Langevelde Jody A. Ettema Maurice Donners Michiel F. WallisDeVries Dick Groenendijk 《Biological conservation》2011,(9):2274-2281
During the last decades, artificial night lighting has increased globally, which largely affected many plant and animal species. So far, current research highlights the importance of artificial light with smaller wavelengths in attracting moths, yet the effect of the spectral composition of artificial light on species richness and abundance of moths has not been studied systematically. Therefore, we tested the hypotheses that (1) higher species richness and higher abundances of moths are attracted to artificial light with smaller wavelengths than to light with larger wavelengths, and (2) this attraction is correlated with morphological characteristics of moths, especially their eye size. We indeed found higher species richness and abundances of moths in traps with lamps that emit light with smaller wavelengths. These lamps attracted moths with on average larger body mass, larger wing dimensions and larger eyes. Cascading effects on biodiversity and ecosystem functioning, e.g. pollination, can be expected when larger moth species are attracted to these lights. Predatory species with a diet of mainly larger moth species and plant species pollinated by larger moth species might then decline. Moreover, our results indicate a size-bias in trapping moths, resulting in an overrepresentation of larger moth species in lamps with small wavelengths. Our study indicates the potential use of lamps with larger wavelengths to effectively reduce the negative effect of light pollution on moth population dynamics and communities where moths play an important role. 相似文献
18.
A quantitative and confirmatory method for the analysis of trinexapac (free acid metabolite of trinexapac-ethyl) in wheat is described. Residues were extracted from wheat with acetonitrile in aqueous phosphate buffer (pH 7) overnight. The extract was directly injected into the HPLC system. Chromatographic separation was achieved on an octadecylsilica column, and detection was performed by negative ion electrospray ionization tandem mass spectrometry. The precursor ion of trinexapac [M - H](-) at m/z 223 was subjected to collisional fragmentation with argon to yield two intense diagnostic product ions at m/z 135 and 179, respectively. Accuracy and specificity for routine analysis of trinexapac were demonstrated. The validated concentration range was 10-200 microg/kg based on a 0.10 g/mL wheat sample extract. Recoveries were within the range of 71-94%, with associated relative standard deviations better than 10%. The limit of detection for trinexapac in wheat was estimated at 5 microg/kg. The method has been applied to a survey of 100 samples of wheat. In 46% of the samples analyzed, a quantifiable amount of trinexapac was detected, ranging from 10 to 110 microg/kg. It has been demonstrated that analyses of trinexapac accurately reflect the total amount of residues of the plant growth regulator, trinexapac-ethyl, in the wheat samples following field application. No residues of the parent compound, trinexapac-ethyl, in wheat were detected. 相似文献
19.
Belletti N Ndagijimana M Sisto C Guerzoni ME Lanciotti R Gardini F 《Journal of agricultural and food chemistry》2004,52(23):6932-6938
The aim of this research was to assess the antimicrobial activity of nine different industrial essences used in a soft drink factory in relation to their composition, as well as to verify the role of vapor pressure on their bioactivity. The essences were tested against a Saccharomyces cerevisiae strain isolated from spoiled soft drinks. The tests were carried out by adding the essences directly to a liquid medium or into the headspace of closed systems inoculated with the yeast. The headspace composition was evaluated through a solid phase microextraction-gas chromatography technique. The use of a mass spectrometer allowed the identification of the peaks detected. The microbial growth was indirectly monitored by measuring the metabolic CO2 released by the yeast. The results obtained indicated that the most effective essences were characterized by the highest concentration of some terpenes, such as citral, beta-pinene, and p-cymene. Moreover, all of the essences were more bioactive when added directly to the liquid medium. 相似文献
20.