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41.
Mathieu Jonard Frédéric André François Jonard Nicolas Mouton Pierre Procès Quentin Ponette 《Annals of Forest Science》2007,64(2):141-150
Total Soil Respiration (TSR) was measured in pure and mixed stands of oak and beech and was partitioned into two contributions using the forest floor removal technique: Mineral Soil Respiration (MSR) and Forest Floor Respiration (FFR). In addition, laboratory incubations of the forest floor and the Ah horizon were performed to evaluate the heterotrophic respiration and the DOC production of these horizons. The relationships between soil temperature and the various soil respiration contributions in the three stands were compared using Q 10 functions. In situ, significant differences (α = 0,05) between stands were observed for the R 10 parameter (respiration rate at 10 °C) of the TSR, MSR and FFR contributions, while only the temperature sensitivity (Q 10) of TSR was significantly affected by stand composition. The effect of soil water content was only significant on MSR and followed different patterns according to stand composition. Under controlled conditions, the R 10 of the forest floor and of the Ah horizon varied with stand composition and the Q 10 of the forest floor decreased in the order: oak (2.27) > mixture (2.01) > beech (1.71). 相似文献
42.
Xavier Cavard Laurent Augusto Etienne Saur Pierre Trichet 《Annals of Forest Science》2007,64(8):875-881
European gorse (Ulex europaeus L.) N2 fixation rate (%Ndfa) was studied in a maritime pine (Pinus pinaster Aït.) oligotrophic forest. Fertilization field trials were carried out on 5 sites with various inputs of phosphorus (0–240 kg P2O5·ha?1). Seven to ten years after pine planting, gorse were sampled to evaluate the effect of P fertilization on gorse %Ndfa, determined using the 15N natural abundance method. One of the prerequisites of this method is the existence of a significant difference between the 15N/14N ratios in the atmospheric N reference and in the stand soil N references. This prerequisite was satisfied for 80 of 120 cases. The average %Ndfa was high (70 ± 3%) but with high local variability. No significant difference in %Ndfa was detected among P treatments. Nitrogen concentration of gorse was significantly higher in the highest dose treatments compared to the control. 相似文献
43.
Amara-Dali WB Lesieur P Artzner F Karray N Attia H Ollivon M 《Journal of agricultural and food chemistry》2007,55(12):4741-4751
Crystallization and melting properties of triacylglycerols (TGs) in anhydrous goat's milk fat (AGMF) are investigated by X-ray diffraction as a function of temperature (XRDT) coupled with high-sensitivity differential scanning calorimetry (DSC), using synchrotron radiation and Microcalix. The polymorphic behavior of AGMF was monitored by varying the cooling rates between 5 and 1 degrees C/min from 45 to -20 degrees C with their subsequent melting at 1 degrees C/min. Quenching of AGMF at -20 degrees C was also examined to determine the metastable polymorphic form of AGMF. At intermediate cooling rates, TGs in AGMF crystallize, from about 18 degrees C in two different lamellar structures with triple chain length 3Lalpha stacking of 72 A and a double chain length 2Lalpha stacking of 48 A, which are correlated to two overlapped exothermic peaks recorded by DSC. A reversible transition sub alpha <--> alpha was observed. Subsequent heating at 1 degrees C/min shows numerous structural rearrangements before final melting. At fast cooling of AGMF (5 degrees C/min), similar unstable crystalline varieties are formed while three endotherms are recorded. Several new unstable lamellar structures are observed after quenching. All of these data are compared to those previously reported at slow cooling (0.1 degrees C/min) showing a relative stability of the structures formed. In spite of general similitude, the thermal and structural behavior of the goat's milk is more complex than that of the cow's milk. 相似文献
44.
Abdel-Aal el-SM Young JC Rabalski I Hucl P Fregeau-Reid J 《Journal of agricultural and food chemistry》2007,55(3):787-794
Selected primitive and modern wheat species were evaluated on the basis of their carotenoid composition and effects of the genotype and environment on lutein using spectrometry and liquid chromatography. Carotenoids in the wheat extracts were identified and confirmed on the basis of their UV/vis and mass spectra compared with those of authentic standards. The protonated molecule (M + 1)+ at m/z 569 was the predominant ion for zeaxanthin compared to the fragment ion at m/z 551 for lutein. A similar carotenoid profile was obtained for the wheat species investigated, but significant differences were observed in the concentration of carotenoids. Einkorn (Triticum monococcum) exhibited the highest level of all-trans-lutein, averaging 7.41 microg/g with small amounts of all-trans-zeaxanthin, cis-lutein isomers, and beta-carotene. Durum, Kamut, and Khorasan (Triticum turgidum) had intermediate levels of lutein (5.41-5.77 microg/g), while common bread or pastry wheat (Triticum aestivum) had the lowest content (2.01-2.11 microg/g). Lutein in einkorn appeared to be influenced significantly by environmental growing conditions. 相似文献
45.
Diversity of insecticide resistance mechanisms and spectrum in European populations of the codling moth, Cydia pomonella 总被引:1,自引:0,他引:1
Reyes M Franck P Charmillot PJ Ioriatti C Olivares J Pasqualini E Sauphanor B 《Pest management science》2007,63(9):890-902
Only a few of the registered insecticides against Cydia pomonella L. are still effective in areas where insecticide resistance has emerged in this pest. Resistance mechanisms are multiple, and their lone or cumulative effects in a single population are not completely understood. A detailed estimation of resistance spectrum is still required to define the suitable insecticides to use against a given population. The efficacy of ten insecticides was therefore investigated together with the resistance mechanisms expressed in four laboratory strains and 47 field populations of C. pomonella from five countries. Bioassays were performed using topical applications of diagnostic concentrations on diapausing larvae, and resistance mechanisms were analysed on adults emerging from control insects. All populations exhibited a reduced susceptibility to at least one insecticide when compared with the susceptible laboratory strain. Cross-resistances were observed between azinphos-methyl or phosalone and more recent compounds such as spinosad and thiacloprid. Resistances to azinphos-methyl, diflubenzuron, spinosad, tebufenozide and thiacloprid were significantly correlated with mixed-function oxidase activity, while increased glutathione-S-transferase and reduced non-specific esterase activities were correlated with resistance to azinphos-methyl and emamectin, respectively. Conversely, resistances to azinphos-methyl, tebufenozide and thiacloprid were negatively correlated with increased esterase activity. None of the observed mechanisms explained the loss of susceptibility of populations to chlorpyrifos-ethyl, and no significant correlation was detected between resistance to deltamethrin and the presence of the kdr mutation. The suitability of such non-target instars to monitor insecticide resistance in field populations is discussed. 相似文献
46.
47.
Using patch studies to link mesoscale patterns of feeding and growth in larval fish to environmental variability 总被引:1,自引:0,他引:1
We present results from a series of three patch studies designed to examine links between environmental variability and mesoscale patterns of feeding and growth of larval radiated shanny ( Ulvaria subbifurcata ). We examine the effects of variability in temperature, turbulence and prey concentration on both the mean (i.e. population level) and the variance (i.e. individual level) of larval feeding and growth rates among the three bays. Although both gut fullness and growth rates differ significantly between bays, our results show only weak environmental influences. When larvae are pooled across bays (i.e. treated as independent observations), environmental factors generally explain <4% of the variability in gut fullness. When treated as daily mean residuals, however, temperature accounts for 41% of the variability in mean gut fullness, while both temperature and prey concentration also explain significant portions of the variance in gut fullness (38 and 43%, respectively). Between-bay differences in larval growth rates are consistent with patterns of temperature variation but not with patterns of prey availability. Studies relying on tracking a single patch of larvae typically suffer from having too few observations to detect significant relationships between feeding or growth and environmental variables. By following three patches we collected a larger number of observations. However, as we encountered only a limited range of environmental conditions it remains difficult to adequately assess the role of environmental factors. In part, this problem stems from the inability of fisheries oceanographers to track the recent environmental history of individual larvae on the same fine scales currently employed to collect biological data (e.g. guts and otoliths) on individuals. 相似文献
48.
Lionel Dégremont Bruno Ernande Pierre Boudry 《Aquaculture (Amsterdam, Netherlands)》2007,262(1):41-53
The multidisciplinary project “MOREST” aims to improve our understanding of causes of summer mortality in Crassostrea gigas juveniles in France and to reduce its impact on oyster production. As part of the MOREST project, 43 full-sib families nested within 17 half-sib families were produced, planted out and tested in 3 sites during summer 2001 to assess to what extent genetic variability exists for this trait. A strong genetic basis was found for survival as narrow-sense heritability estimates ranged from 0.47 to 1.08, with higher values in sites where summer mortality was higher. Genetic correlations across sites were positive and very high for survival, indicating no genotype by environment interaction. In contrast, lower genetic variation was observed for growth in all sites. Finally, genetic correlations between growth and survival were low, in all sites. Selective breeding in a single site should therefore be an efficient means of improving survival in oysters less than one year old along the French Atlantic and Channel coastlines with only very limited effects on growth. As yield mostly depends on survival and growth, this approach should significantly improve harvestable yield. Possible reasons why a high genetic variance for survival appears to be maintained in wild populations are discussed. 相似文献
49.
Pierre Trpanier Cecile Sguin Yolande Bastien Gaston Boulay Gilles Lussier Michel Trudel 《Veterinary microbiology》1985,10(6):517-523
Using C57BL/HPB mouse erythrocytes, hemagglutination has been observed with the Los Angeles and Colorado-1 strains of bovine herpesvirus type 1 and with 12 other Canadian field isolates as well. The specificity of the hemagglutination observed with the viral strains has been confirmed by a hemagglutination-inhibition assay. 相似文献
50.
Maria Laura Boschiroli Safia Ouahrani-Bettache Vincent Foulongne Sylvie Michaux-Charachon Gisele Bourg Annick Allardet-Servent Chantal Cazevieille Jean-Phillipe Lavigne Jean Pierre Liautard Michel Ramuz David OCallaghan 《Veterinary microbiology》2002,90(1-4)
The type IV secretion system, encoded by the virB region, is a key virulence factor for Brucella. The 12 genes of the region form an operon that is specifically induced by phagosome acidification in cells after phagocytosis. We speculate that the system serves to secrete unknown effector molecules, which allow Brucella to pervert the host cell endosomal pathways and to create a novel intracellular compartment in which it can replicate. 相似文献