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101.
Population parameters (mortality of females, reproductive success, longevity of juveniles) of the common woodlouse, Porcellio scaber (Isopoda, Oniscidea), were examined with respect to the influence of varying leaf litter attributes: pH level, microbial
cellulase activity, microbial dehydrogenase activity, protein content, nitrogen content, water content, tannin content, total
phenol content and toughness of the leaves. These attributes were combined by using Principal Component Analysis. We obtained
three Principal Components (PC) that were defined as “acidification,”“microorganisms” and “tree species.” The PCs explained
85% of the variance of leaf litter attributes. The PC “acidification” mainly influenced the mortality of females (P<0.001), while the longevity of juveniles showed significant correlation to the PC “microorganisms” (P<0.05). The PC “tree species” showed no influence on the observed population parameters, indicating that the leaf litter species
itself had no direct influence on the population parameters of P. scaber. The reproductive success of females could not be explained by either of the PCs, but was influenced by cellulolytically
active microorganisms (P<0.01). From these results, we conclude that acidification and reduced microbial activity in the field will cause a decrease
in population density of P. scaber.
Received: 30 July 1996 相似文献
102.
The simulation model SIDRA is based on a semi-analytical and semi-numerical solution to the Boussinesq equation. It has been developed on the ground of theoretical and field experimental results with the aim of a good prediction of both drainage peak and recession flow rates. Theoretical aspects and basic equations of the model are presented for the most general case where both soil physical properties and water table shapes are depth-dependent. The parameter sensitivity and field performances of the model are estimated in shallow loamy soils facing a seasonal waterlogging during winter season in France. Water table shape factors are the most sensitive parameters. Drainable porosity is slightly more sensitive than hydraulic conductivity for drainflow rate prediction whereas hydraulic conductivity is slightly more sensitive for water table elevation prediction. A comparison of experimental and simulated long term discharge and water table exceedance duration curves shows that the model could be a useful tool to assess the performances and control the relevance of a given subsurface drainage design.
Résumé Le modèle de simulation SIDRA est basé sur une résolution semi-analytique et semi-numérique de l'équation de Boussinesq. Il a été développé à partir d'une approche théorique et de l'analyse de résultats d'expérimentations de terrain avec pour principal objectif d'atteindre une bonne prédiction des débits de pointe et de tarissement. Les principales équations du modèles sont présentées dans leur forme la plus générale qui permet de prendre en compte des propriétés hydrodynamiques et des formes de nappe dépendantes de la profondeur. L'étude de sensibilité aux paramètres et l'évaluation des performances du modèle sont réalisées dans le cas de sols limoneux peu profonds, sur la période hivernale où se manifeste l'engorgement des sols en France. Le modèle est très sensible aux variations des facteurs de forme de nappe. Concernant les paramètres hydrodynamiques, les débits simulés sont plus sensibles aux variations de la porosité de drainage qu'à celles de la conductivité hydraulique. A l'inverse les hauteurs de nappe simulées sont plus sensibles aux variations de conductivité hydraulique. Une comparaison sur une longue période des fréquences de dépassement de débits et hauteurs de nappe, simulées et observées, montre que le modèle peut constituer un bon outil de contrôle de l'efficacité d'un réseau de drainage et de son dimensionnement.相似文献
103.
104.
Matthieu Guillemain Olivier Devineau Jean-Yves Mondain-Monval Géraldine Simon 《Biological conservation》2007,137(4):567-576
The negative consequences of lead shot ingestion have been demonstrated in captive birds, and the prevalence of embedded shot has been measured in wild waterfowl several times. However, the long-term consequences of these two indirect outcomes of hunting on waterfowl survival have merely been investigated. Using data from about 40,000 X-rayed teals (Anas crecca), this study attempts to evaluate these effects. We used multivariate logistic regressions to model the probability of carrying shot in the flesh or in the gizzard while testing for various explanatory variables such as sex, age, time or morphological measures like mass and flattened wing length. Because of technical issues, we used a non-parametric sign test rather than a complete capture-recapture analysis to evaluate the effect of shot on teal survival. This test was applied to the differences in time between ringing and recovery for lead categories (no lead shot, ?1 shot in the flesh but none in the gizzard, ?1 shot in the gizzard but none in the flesh) compared two by two. We show that, overall, males are more likely to carry embedded shot than females whereas the latter are more likely to carry lead pellets in the gizzard. Similarly, adults are more likely to carry shot in the flesh whereas first year individuals are more likely to have pellets in the gizzard. Embedded shot tend to accumulate in the ducks body over time, i.e. with the number of encounters with hunters, with no significant effect on survival. Conversely, the probability of carrying shot in the gizzard decreases over time, because lead-poisoning quickly leads the individual to death. Several possible biological interpretations are put forward to explain those results. This study demonstrates that negative impacts of ingested lead on teal survival arise after only one single pellet is ingested, advocating the ban of lead ammunition. 相似文献
105.
106.
Kuo A Gulbis JM Antcliff JF Rahman T Lowe ED Zimmer J Cuthbertson J Ashcroft FM Ezaki T Doyle DA 《Science (New York, N.Y.)》2003,300(5627):1922-1926
The KirBac1.1 channel belongs to the inward-rectifier family of potassium channels. Here we report the structure of the entire prokaryotic Kir channel assembly, in the closed state, refined to a resolution of 3.65 angstroms. We identify the main activation gate and structural elements involved in gating. On the basis of structural evidence presented here, we suggest that gating involves coupling between the intracellular and membrane domains. This further suggests that initiation of gating by membrane or intracellular signals represents different entry points to a common mechanistic pathway. 相似文献
107.
Harvey RJ Depner UB Wässle H Ahmadi S Heindl C Reinold H Smart TG Harvey K Schütz B Abo-Salem OM Zimmer A Poisbeau P Welzl H Wolfer DP Betz H Zeilhofer HU Müller U 《Science (New York, N.Y.)》2004,304(5672):884-887
Prostaglandin E2 (PGE2) is a crucial mediator of inflammatory pain sensitization. Here, we demonstrate that inhibition of a specific glycine receptor subtype (GlyR alpha3) by PGE2-induced receptor phosphorylation underlies central inflammatory pain sensitization. We show that GlyR alpha3 is distinctly expressed in superficial layers of the spinal cord dorsal horn. Mice deficient in GlyR alpha3 not only lack the inhibition of glycinergic neurotransmission by PGE2 seen in wild-type mice but also show a reduction in pain sensitization induced by spinal PGE2 injection or peripheral inflammation. Thus, GlyR alpha3 may provide a previously unrecognized molecular target in pain therapy. 相似文献
108.
109.
Kivelson MG Khurana KK Russell CT Volwerk M Walker RJ Zimmer C 《Science (New York, N.Y.)》2000,289(5483):1340-1343
On 3 January 2000, the Galileo spacecraft passed close to Europa when it was located far south of Jupiter's magnetic equator in a region where the radial component of the magnetospheric magnetic field points inward toward Jupiter. This pass with a previously unexamined orientation of the external forcing field distinguished between an induced and a permanent magnetic dipole moment model of Europa's internal field. The Galileo magnetometer measured changes in the magnetic field predicted if a current-carrying outer shell, such as a planet-scale liquid ocean, is present beneath the icy surface. The evidence that Europa's field varies temporally strengthens the argument that a liquid ocean exists beneath the present-day surface. 相似文献
110.
Zimmer C 《Science (New York, N.Y.)》1999,283(5410):1989-1990