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A large proportion of leaf fluoride consists of surface deposits and a sucking herbivore would be expected to take in a smaller load of fluoride in its food than a chewing herbivore. In these experiments, fluoride was applied aerially, through the leaves, and systemically, via the roots, to compare uptake by aphids and effects on their fecundity. Fluoride applied via roots was taken up by both the plants and the aphids, but at high treatment rates the aphids had much lower concentrations than the foliage. When the plants and aphids were fumigated with HF the aphids had much greater loads than the plant shoots, which was due to deposition of F on the insect surfaces. There were no effects of the treatments on aphid reproduction or development time. The aphids obtained some fluoride through their diet which suggests that fluoride is present in the phloem sap, previously thought to be of minor importance. 相似文献
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上海港近年来对可持续发展战略十分重视,在港口经济发展的同时十分重视环境保护,坚持贯彻落实党和国家环境保护的各项方针政策和法律法规,坚持环保科技投入,强化环境管理,保持港区水陆域环境和生态环境,以港兴城,为城市经济可持续发展服务。 相似文献
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In large-eddy simulations of atmospheric boundary layer turbulence, the lumped coefficient in the eddy-diffusion subgrid-scale
(SGS) model is known to depend on scale for the case of inert scalars. This scale dependence is predominant near the surface.
In this paper, a scale-dependent dynamic SGS model for the turbulent transport of reacting scalars is implemented in large-eddy
simulations of a neutral boundary layer. Since the model coefficient is computed dynamically from the dynamics of the resolved
scales, the simulations are free from any parameter tuning. A set of chemical cases representative of various turbulent reacting
flow regimes is examined. The reactants are involved in a first-order reaction and are injected in the atmospheric boundary
layer with a constant and uniform surface flux. Emphasis is placed on studying the combined effects of resolution and chemical
regime on the performance of the SGS model. Simulations with the scale-dependent dynamic model yield the expected trends of
the coefficients as function of resolution, position in the flow and chemical regime, leading to resolution-independent turbulent
reactant fluxes. 相似文献
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The atmospheric boundary layer adjustment at the abrupt transition from a canopy (forest) to a flat surface (land or water) is investigated in a wind tunnel experiment. Detailed measurements examining the effect of canopy turbulence on flow separation, reduced surface shear stress and wake recovery are compared to data for the classical case of a solid backward-facing step. Results provide new insights into the interpretation for flux estimation by eddy-covariance and flux gradient methods and for the assessment of surface boundary conditions in turbulence models of the atmospheric boundary layer in complex landscapes and over water bodies affected by canopy wakes. The wind tunnel results indicate that the wake of a forest canopy strongly affects surface momentum flux within a distance of 35–100 times the step or canopy height, and mean turbulence quantities require distances of at least 100 times the canopy height to adjust to the new surface. The near-surface mixing length in the wake exhibits characteristic length scales of canopy flows at the canopy edge, of the flow separation in the near wake and adjusts to surface layer scaling in the far wake. Components of the momentum budget are examined individually to determine the impact of the canopy wake. The results demonstrate why a constant flux layer does not form until far downwind in the wake. An empirical model for surface shear stress distribution from a forest canopy to a clearing or lake is proposed. 相似文献
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Experiments to assess the impact of dietary fluoride on larvae of Pieris brassicae were designed to substantiate field observations that at polluted sites little fluoride is absorbed by insect larvae and that most of the body load is caused by surface contamination. Treatment with fluoride as HF or AlF3 had no effect on pupal weight of Pieris and we conclude that fluoride, at concentrations likely to be found on vegetation at polluted sites, is unlikely to have a direct impact on the growth of chewing herbivores. Fluoride in the gut formed the biggest component of the total body load. A significant amount of fluoride was detected in exuviae, but resulted from surface contamination. When larvae from polluted food were transferred to untreated food it took several days for the fluoride content of the faeces to return to background levels. 相似文献
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The social organization of gregarious lemurs significantly deviates from predictions of the socioecological model, as they
form small groups in which the number of males approximately equals the number of females. This study uses models of reproductive
skew theory as a new approach to explain this unusual group composition, in particular the high number of males, in a representative
of these lemurs, the redfronted lemur (Eulemur fulvus rufus). We tested two central predictions of “concession” models of reproductive skew theory, which assume that subordinates may
be allowed limited reproduction by dominant group members as an incentive to remain in the group, thereby increasing the group’s
overall productivity. Accordingly, relatives are predicted to receive less reproduction than non-relatives, and the overall
amount of reproductive concessions given to subordinates is predicted to increase as the number of subordinates increases.
In addition, we tested whether the number of females in a group, a variable not previously incorporated in reproductive skew
theory, affected reproductive skew among males. Using microsatellite analyses of tissue DNA, we determined paternities of
49 offspring born into our study population in Kirindy forest (western Madagascar) since 1996 to determine patterns of male
reproductive skew to test these predictions. Our analyses revealed remarkable reproductive skew, with 71% of all infants being
sired by dominant males, but both predictions of reproductive skew models could not be supported. Instead, the number of females
best predicted the apportionment of reproduction among the males in this species, suggesting that current reproductive skew
models need to incorporate this factor to predict reproductive partitioning among male primates and perhaps other group-living
mammals.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
Both Peter M. Kappeler and Markus Port contributed equally to this paper. 相似文献
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