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71.
Summary We tested the role of a grasshopper defensive secretion in deterring lizard predation. Adults, but not young larvae, of the chemically defended lubber grasshopperRomalea guttata (=microptera) froth a volatile secretion when attacked by predators. The lizardAnolis carolinensis failed to strike juvenile lubbers (which lack secretion) in laboratory trials. Survivorship of palatable crickets loaded with secretion offered toA. carolinensis was not significantly different from survivorship of control crickets. In experiments designed to investigate if lizards learn an aversion to the secretion, striking times forSceloporus undulatus fed wax worms coated with secretion were not significantly different over three days of trials. Three primary conclusions are drawn from these data. First, the secretion may not be necessary for lubber protection from lizards. Second, lubber secretion does not appear to deter lizards from attacking or eating prey items. Third, lizards do not appear to develop an aversion to the secretion. 相似文献
72.
Tov Elperin Nathan Kleeorin Michael A. Liberman Victor S. L’vov Igor Rogachevskii 《Environmental Fluid Mechanics》2007,7(2):173-193
A mechanism of formation of small-scale inhomogeneities in spatial distributions of aerosols and droplets associated with
clustering instability in the atmospheric turbulent flow is discussed. The particle clustering is a consequence of a spontaneous
breakdown of their homogeneous space distribution due to the clustering instability, and is caused by a combined effect of
the particle inertia and a finite correlation time of the turbulent velocity field. In this paper a theoretical approach proposed
in Elperin et al. (2002) Phys Rev E 66:036302 is further developed and applied to investigate the mechanisms of formation
of small-scale aerosol inhomogeneities in the atmospheric turbulent flow. The theory of the particle clustering instability
is extended to the case when the particle Stokes time is larger than the Kolmogorov time scale, but is much smaller than the
correlation time at the integral scale of turbulence. We determined the criterion of the clustering instability for the Stokes
number larger than 1. We discussed applications of the analyzed effects to the dynamics of aerosols and droplets in the atmospheric
turbulent flow. 相似文献
73.
Malanichev A Mantseva E Shatalov V Strukov B Vulykh N 《Environmental pollution (Barking, Essex : 1987)》2004,128(1-2):279-289
The numerical evaluation of selected PCB congener (28, 118, 153, 180) transport over the Northern Hemisphere is carried out for 1996 using MSCE-POP model. This model is a multicompartment three-dimensional one and includes various environmental media such as the atmosphere, soil, vegetation, seawater, and sea ice. The spatial resolution is 2.5 degrees x2.5 degrees for all media except marine one (1.25 degrees x1.25 degrees ). The main model output information is deposition fluxes, spatial distribution of concentrations in environmental media, pathways and source-receptor relationships. Calculation results are analysed for the whole hemisphere and the Arctic region. In particular, this gives an opportunity to estimate the contributions of individual emission source groups to the Arctic pollution. The reliability of the model assessment is analysed by comparison between calculated and observed data. 相似文献
74.
A comparative study was conducted at three stations on a fourth order Nigerian stream to evaluate the effects of a road and bridge construction on the macrobenthic invertebrates of the bank-root biotope. Siltation and sedimentation appear to be the important factors affecting macroinvertebrates. At station 2, the construction site, there was a considerable reduction in the occurrence and abundance of invertebrate taxa; different groups of invertebrates showed varying responses to perturbational stress; the taxa richness, general diversity and evenness were also low. Irregular fluctuations in diversity and evenness suggested that the benthic community of station 2 was less stable than those of upstream and downstream stations. The concentrated dominance of Ephemeroptera and Coleoptera at station 2, despite low diversity, reflected the ability of a few tolerant taxa to occur there in high abundance. Faunal comparisons of the three stations confirmed the perturbational stress caused by construction activities. 相似文献
75.
Cheuk W Lo KV Copeman R Joliffe P Fraser BS 《Journal of environmental science and health. Part. B》2005,40(3):449-461
This study investigated the disease suppression abilities of a compost amendment that was added to the conventional growing medium, yellow cedar sawdust, used in most British Columbia vegetable greenhouses. The compost amendment was produced in a controlled, in-vessel process primarily from greenhouse crop waste materials. The pathogen and cultivar under study were Fusarium oxysporum f. sp. radicis-lycopersici (FORL) on Dombito (FORL-susceptible) beefsteak greenhouse tomatoes. Significant reduction of Fusarium crown and root rot was also realized in tomato seedlings by applying compost amendment from several different batches, as a seed cover or plug substitute. In a greenhouse trial, disease suppression using a mixture of 2:1 sawdust to amendment by volume was shown to be most effective. As a result, the tomato yield over a nine-month growing season was improved by 74% where the medium was deliberately infested with FORL. 相似文献
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