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排序方式: 共有149条查询结果,搜索用时 15 毫秒
31.
Bergerot Benjamin Lemasle Pierre-Gilles Boussard Hugues Betbeder Julie Jambon Olivier Georges Romain Croci Solène Burel Françoise Baudry Jacques 《Landscape Ecology》2022,37(1):159-174
Landscape Ecology - To analyze the scales at which landscape structure influences ecological processes, two approaches with different underlying ecological assumptions exist; the usual threshold... 相似文献
32.
The behaviour of imazapyr (2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)nicotinic acid), a broad spectrum herbicide of the imidazolinone family, has been studied under UV radiation in the presence of metal salts. Complexation interactions between imazapyr and metal ions decreased imazapyr photolysis. A chemometric study compared the photodegradation of imazapyr in aqueous solutions in the presence of Na+, Ca2+ or Cu2+ and their concomitant anionic species (Cl-, NO3-) at various pesticide/metal ion molar ratios. The study showed the major role of metal ions in the degradation of imazapyr and its main photoproducts. The molecules were strongly stabilised on complexation with metal ions, leading to an increase in persistence of the pesticide. 相似文献
33.
34.
Georges Kunstler Robert B. Allen David A. Coomes Charles D. Canham Elaine F. Wright 《Annals of Forest Science》2013,70(3):287-298
Context
There is strong interest in sustainable forest management systems that preserve characteristics of forests close to naturalness. Assessing the effectiveness of these systems is difficult because defining “natural” baselines from which impacts are estimated is challenging and because the influence of harvesting can have complex interactions with major natural disturbances.Aims
We used SORTIE/NZ, an individual tree-based forest dynamics model, to understand how harvesting and earthquake disturbance affect the dynamics of a New Zealand podocarp–angiosperm forest.Methods
Having parameterized SORTIE/NZ with extensive field data, we ran simulations for three natural dynamics scenarios (no disturbance and two earthquake scenarios) and then added podocarp harvesting scenario to each of these.Results
Simulations suggest that this forest is experiencing transient dynamics, with a natural rise in the dominance of one species of slow-growing podocarp with and without earthquake. Harvesting podocarps strongly affected its increase in basal area.Conclusion
Our results indicate that transient dynamics may occur in mixed podocarp forests and major disturbances may have complex interactions with management. Evaluating management impacts without accounting for these complex dynamics may be misleading. Models make predictions about transient trajectories that may help to evaluate these impacts. 相似文献35.
Barbara Chaves Stefaan De Neve Maria del Carmen Lillo Cabrera Pascal Boeckx Oswald Van Cleemput Georges Hofman 《Biology and Fertility of Soils》2005,41(6):411-418
Manipulating the N release from high-N crop residues by simultaneous mixing of these residues with organic biological waste (OBW) materials seems to be a possible method to reduce NO3– leaching. The aim of this study was to examine whether the incorporation of OBW materials together with a high-N crop residue (celery) had also an effect on N2O emission from horticultural soil under short-term and optimised laboratory conditions. A sandy loam soil and celery residues were mixed with different OBW materials and brought into PVC tubes at 80% water-filled pore space and 15°C. Every 2.5 h, a gas sample was taken and analysed by gas chromatography for its N2O concentration. The soil amended with only celery residues had a cumulative N2O emission of 9.6 mg N kg–1 soil in 50 h. When the celery residues were mixed with an OBW material, the N2O emission was each time lower than the emission from the celery-only treatment (between 3.8 and 5.9 mg N kg–1 soil during maximum 77 h), except with paper sludge (17.2 mg N kg–1 soil in 100 h). The higher N2O emission from the paper sludge treatment was probably due to its unusually low C:N ratio. Straw, green waste compost 1 (GWC1) and 2 (GWC2), saw dust, and tannic acid reduced the N2O emission of the celery treatment by 40 to 60%. Although the N2O reduction potential can be expected to be lower and with differing dynamics under field conditions, this study indicates that apart from reducing NO3– leaching, OBW application may at the same time reduce N2O emissions after incorporation of high-N crop residues. 相似文献
36.
Spatial activity and expression of plasma membrane H+-ATPase in stem xylem of walnut during dormancy and growth resumption 总被引:1,自引:0,他引:1
Alves G Decourteix M Fleurat-Lessard P Sakr S Bonhomme M Améglio T Lacointe A Julien JL Petel G Guilliot A 《Tree physiology》2007,27(10):1471-1480
Plasma membrane H+-ATPase (PM H+-ATPase) plays a key role in nutrient transport, stress responses and growth. To evaluate proton motive force differences between apical and basal parts of acrotonic 1-year-old shoots of walnut (Juglans regia L. cv 'Franquette') trees, spatial and seasonal changes in PM H+-ATPase were studied in mature xylem tissues. During both the dormancy and growth resumption periods, and in both the apical and basal parts of the stem, PM H+-ATPase activity showed positive correlations with the amount of immunodetectable protein. In spring, at the time of growth resumption, higher activities and immunoreactivities of PM H+-ATPase were found in the apical part of the stem than in the basal part of the stem. In spring, the decrease in xylem sugar concentration reflected the high sugar uptake rate. Our data suggest that PM H+-ATPase plays a major role in the uptake of carbohydrates from xylem vessels during growth resumption. These results are discussed in the context of the acrotonic tendency of walnut shoots. 相似文献
37.
Alves G Ameglio T Guilliot A Fleurat-Lessard P Lacointe A Sakr S Petel G Julien JL 《Tree physiology》2004,24(1):99-105
We studied seasonal variation in xylem sap pH of Juglans regia L. Our main objectives were to (1) test the effect of temperature on seasonal changes in xylem sap pH and (2) study the involvement of plasma membrane H+-ATPase of vessel-associated cells in the control of sap pH. For this purpose, orchard-grown trees were compared with trees grown in a heated (> or = 15 degrees C) greenhouse. During autumn, sap pH was not directly influenced by temperature. A seasonal change in H+-ATPase activity resulting from seasonal variation in the amount of protein was measured in orchard-grown trees, whereas no significant seasonal changes were recorded in greenhouse-grown trees. Our data suggest that H+-ATPase does not regulate xylem sap pH directly by donating protons to the xylem, but by facilitating secondary active H+/sugar transport, among other mechanisms. 相似文献
38.
Theves G 《Historia medicinae veterinariae》2002,27(1-4):107-129
39.
Relationship between ketosis and dairy cows’ blood metabolites in intensive production farms of the periurban area of Dakar 总被引:2,自引:0,他引:2
Yameogo N Ouedraogo GA Kanyandekwe C Sawadogo GJ 《Tropical animal health and production》2008,40(7):483-490
This study which involved 140 Holstein and Montbeliard was carried out in the periurban area of Dakar with the aim to establish the relationship between ketosis, milk production and biochemical blood metabolites. The results showed that ketosis is a real problem in periurban farms around the city of Dakar with high proportions of 33.57% for subclinical ketosis and 6.43% for clinical ketosis. In their second month of milking, cows with subclinical ketosis had a decrease of 12.4 and 15.,6% in milk yield respectively for Montbeliard and Holstein, whereas cows with clinical ketosis had a decrease of 18.6 and 26%. Ketogenic cows (subclinical and clinical) have significantly lower average levels of blood glucose (p<0.05) and significantly higher average levels of blood urea (p<0.05) than cows with normal blood beta-Hydroxy Butyrate (BbHB) levels. Also, from one farm to another, significant difference was recorded with concentration of total proteins and globulin, calcium and magnesium. 相似文献
40.
Georges Obolensky Ing. Agr. BSc MSc Dr. Ing. DSc. 《Plant foods for human nutrition (Dordrecht, Netherlands)》1959,5(4):344-366
Summary In view of a preliminary investigation of liquid-solid extraction by means of Ultra-sonic waves, the effects of 300, 500 and 2000 kHz insonation was tried, using 50° alcohol and vanilla beans.The experimental results were calculated on a 12 hours extraction base, with a 250 ml Kumagawa.Our experiments have shown that an extraction efficiency of 94%, after 12 min. insonation, can be obtained, but that this efficiency seemed, in our particular case, to be closely correlated with the moisture content of the sample.Besides, the classical extraction in a Kumagawa showed, that such acquired caracters, as increased percentage in vanillin and oleoresines obtained after an ultrasonic irradiation remained stable.
Zusammenfassung Ein Versuch wurde angestellt, Vanille-Extraktion mit Hilfe von Ultraschallwellen durchzuführen.Frequenzen von 300, 500 und 2000 kHz mit Intensitäten von 3,4–13 W/cm2 und Extraktionsdauer, von 3–12 Min., wurden dazu verwendet.Die erzielten Ergebnisse haben deutlich gezeigt, dass unter günstigen Versuchsbedingungen, nach 12 min. Beschallung 94% einer klassischen Extraktion von 12 Stunden mit dem Apparat nachKumagawa, erzielt werden kann.Es scheint jedoch, dass in diesem besonderen Falle die Wirksamkeit der Extraktion vom Feuchtigkeitsgehalt des Vanillenmusters abhängt.Von grossem Interesse ist der Befund, dass der erhöhte Vanillinund Oelsubstanzen-(Oleoresine) Gehalt, der beschallten Vanille-schoten, stabil ist.Hiermit werden neue und interessante Entwicklungsmöglichkeiten dieser neuen Wissenschaft in der Zukunft eröffnet.相似文献