A comparison of alternative modelling approaches to evaluate the European forest carbon fluxes     

Boris Ťupek  Giuliana Zanchi  Pieter J. Verkerk  Galina Churkina  Nicolas Viovy  John K. Hughes  Marcus Lindner 《Forest Ecology and Management》2010

The European forest carbon balance studied by various methods shows different results. We compared the regional and national net primary production (NPP) estimated by the forest inventory-based model EFISCEN and the climate-based terrestrial ecosystem models (TEMs: BIOME-BGC, ORCHIDEE, and JULES), and single forests NPP derived from the international network of eddy-covariance towers (FLUXNET). In addition, the paper presents the net ecosystem production (NEP) and the net biome production (NBP) calculated with EFISCEN and discusses the influence of forest management onto carbon fluxes. We aimed to better understand the variance between EFISCEN and TEMs NPP estimates, and to improve the assessment of European forest mitigation potential for the year 2005.  相似文献   

Interactions between hormonal and developmental signalling in the prevention of side-shoots in rose (Rosa hybrida L.)     

Nicodemus Ndawa Musembi  Nicolas Adeya  Winnie Wanjiku Murigi 《The Journal of Horticultural Science and Biotechnology》2013,88(5):419-423

Summary

This study investigated the effects of auxin sprays on the development of side-shoots in rose (Rosa hybrida L.). The rationale was to prevent or to minimise side-shoot development in a commercially acceptable rose cultivar. Equallyspaced doses (at 0, 15, 30, 45 or 60 mg l^–1) of -naphthaleneacetic acid (NAA) were applied at the equivalent of 100 l ha^–1 to roses grown on an inert substrate in a commercial greenhouse, via repeated foliar sprays at 2, 4, or 8 d intervals over 7 weeks. Unattended or hand-pinched plants were used as negative or positive controls, respectively.The interaction between auxin dose and spray interval had a significant (P ≤ 0.001) influence on the number and growth rate of side-shoots on a stem. All auxin doses tested completely prevented side-shoot development on rose stems at a 2 d spray interval. This high efficacy was attributed to prevention of the irreversible phase-change in the regulation of apical dominance. However, the interaction between auxin dose and spray interval significantly (P ≤ 0.001) influenced the occurrence of leaf epinasty, a physiological condition with a negative impact on cut-shoot quality. Bullheads, another undesirable physiological condition, was significantly (P ≤ 0.001) influenced by auxin dose. This novel technology is expected to lower rose production costs. The data obtained in this study demonstrate the interaction between hormonal and developmental signalling in apical dominance. Possible modes of action are discussed.  相似文献   

Structural relationships among vegetation,soil fauna and humus form in a subalpine forest ecosystem: a Hierarchical Multiple Factor Analysis (HMFA)     

Nicolas Bernier  François Gillet 《Pedobiologia》2012,55(6):321-334

Aboveground vegetation, four belowground fauna groups and humus composition have been analyzed in order to investigate the links between autotrophic and heterotrophic communities in a Norway-spruce mountain forest in Tours-en-Savoie (France). The aboveground plant community was recorded in small patches corresponding to contrasting microhabitats. Animal communities and humus layers were sampled within the same patches. The relationships between humus profile, faunistic and floristic compositional gradients were investigated by Multiple Factor Analysis (MFA) and, for the first time in ecology, a Hierarchical Multiple Factor Analysis (HMFA) was used to interpret differences among humus layers. The analysis revealed a pattern with three main groups of microhabitats. The thorough study of separate humus layers could explain this result. The interplay of plant–animal–soil interactions is likely to drive the ecosystem toward three alternative states supporting humus traditional classification between mull–mor–moder. HMFA revealed the importance of depth to explain this contrast among humus forms, using humus layers as diagnostic tools in both inert and living components. HMFA also showed contrast between unexploited and exploited parts of the forest, but the study of soil and vegetation indicate that this contrast does not only hold in forest management but also in geomorphology. RV-coefficients among the six groups of variables showed significant fauna–fauna relationships in almost all humus layers except Actinedida. Plant–soil interactions are not as strong as expected and are even weaker when the soil in question is deep. In addition, HMFA failed to show direct interactions between plant and soil fauna but, paradoxically, HMFA does suggest that indirect plant–fauna interactions are at the focus of the ecosystem strategy that leads to the differentiation of ecological niches within the forest mosaic.  相似文献   

Does the influence of earthworms on water infiltration, nitrogen leaching and soil respiration depend on the initial soil bulk density? A mesocosm experiment with the endogeic species Metaphire posthuma     

Pascal Jouquet  Ga?lle Huchet  Nicolas Bottinelli  Thuy Doan Thu  Toan Tran Duc 《Biology and Fertility of Soils》2012,48(5):561-567

Soil compaction has a negative impact on both earthworm abundance and diversity. Recent studies, however, suggest that earthworm cast properties are not influenced by the initial soil bulk density. With time, earthworms could therefore transform soils with different bulk densities into a soil with the same physical state and thus with a similar ecological functioning. This study aimed to test this hypothesis in two laboratory incubation experiments. First, we measured the influence of soil bulk density (1.1 or 1.4?g?cm^?3) on the production of cast by the endogeic earthworm species Metaphire posthuma. In a second experiment, we investigated the effect of M. posthuma on water infiltration, NH ₄ ⁺ , and NO ₃ ^? leaching and soil respiration at the same two soil bulk densities. Although initially higher, earthworm casting activity in soil at 1.4?g?cm^?3 decreased until it reached the same level of activity as earthworms in soil at 1.1?g?cm^?3. This behavioral plasticity led to a transformation of compacted and loose soils, with their own functioning, to a third and similar state with similar hydraulic conductivity, nitrogen leaching, and soil respiration. The consequences for soil organization and soil functioning are discussed.  相似文献   

Microphytobenthic production estimated by in situ oxygen microprofiling: short-term dynamics and carbon budget implications     

Lionel Denis  Fran?ois Gevaert  Nicolas Spilmont 《Journal of Soils and Sediments》2012,12(10):1517-1529

Purpose

Short-term temporal variability of microphytobenthic primary production is suspected to be of the same magnitude as seasonal variability, but data remain very scarce due to methodological limitations. In this context, a 6-day in situ high-frequency survey was performed in a temperate intertidal mudflat using an automated microprofiling system.

Materials and methods

In situ microphytobenthic primary production was measured using an automated acquisition system for oxygen microprofiles. More than 900 microprofiles, acquired during six consecutive days in April 2008, allowed the establishment of robust relationships between oxygen production and irradiance. Moreover, simultaneous measurements of fluorescence parameters and oxygen microprofiles during two diurnal emersion periods led to significant correlations between relative electron transport rate (rETR) and gross oxygen production (GOP).

Results and discussion

The use of an automated system allowed the estimation of oxygen exchanges during both immersion and emersion periods, and to our knowledge, this is the first study presenting continuous measurements during six consecutive days. The intertidal mudflat studied here was characterized by a maximum net oxygen production of 6.74?mmol?O₂?m^?2?h^?1. Evidence for microphytobenthic migration behavior was observed during several periods and induced important depletion in oxygen production while irradiance remained high. Consequently, estimations of GOP from fitted photosynthesis?Cirradiance curves (P?CI curves) showed an overestimation of 31?% compared to the GOP actually measured during the whole deployment.

Conclusions

This study confirmed that oxygen microsensors may be used to record microphytobenthic primary production, as resulting dynamics agreed with fluorescence data, while production values were in accordance with those presented in the literature. High-frequency microprofiles acquisition may be an easy way to monitor short-term temporal changes in microphytobenthic primary production in order to calculate accurate carbon or oxygen budgets for intertidal areas.  相似文献   

The cholesterol-lowering property of soybeans fed to rats is related to the fasting duration     

Guermani-Nicolle  Lydie  Villaume  Christian  Bau  Hwei-Ming  Schwertz  Annie  Nicolas  Jean-Pierre  Mejean  Luc 《Plant foods for human nutrition (Dordrecht, Netherlands)》2001,56(3):239-249

Numerous factors affect plasma cholesterol and, therefore, representpotential interferences with the specific effects of diet on lipid metabolism.After casein intake, serum cholesterol levels depend on many experimentalconditions in rats, such as the type of casein, the presence or absence ofcholesterol in the diet, the age and strain of rat, the diet composition, thenutritional status. The effect of fasting duration on selected parameters wasstudied in adult male Wistar rats fed a 20% casein and 1% cholesterol-based diet. No changes were observed in total serum, lipoproteins-B andHDL cholesterol and in triglyceride values after an 8 h-fast compared tonon-fasted animals. A significant decrease was induced in total andlipoproteins-B cholesterol with a 12 h-fast. A prolonged fast resulted ina significant decrease in these parameters and in triglycerides and inHDL-cholesterol levels.Fasted animals fed heated soybean meal instead of casein did not display amarked decrease in serum lipids. It appeared that the fasting effect wasmore marked in animals fed casein than in animals fed soybeans. Theseresults showed the importance of experimental conditions such as nutritional status ofanimals when blood samples are taken in studies of the hypocholesterolemiceffect of soy protein compared to casein.  相似文献   

Estimation of transmission parameters of a fluoroquinolone-resistant Escherichia coli strain between pigs in experimental conditions     

Andraud M  Rose N  Laurentie M  Sanders P  Le Roux A  Cariolet R  Chauvin C  Jouy E 《Veterinary research》2011,42(1):44

Antimicrobial resistance is of primary importance regarding public and animal health issues. Persistence and spread of resistant strains within a population contribute to the maintenance of a reservoir and lead to treatment failure. An experimental trial was carried out to study the horizontal transmission of a fluoroquinolone-resistant Escherichia coli strain from inoculated to naïve pigs. All naïve contact pigs had positive counts of fluoroquinolone-resistant E. coli after only two days of contact. Moreover, re-infections of inoculated pigs caused by newly contaminated animals were suspected. A maximum likelihood method, based on a susceptible-infectious-susceptible (SIS) model, was used to determine the transmission parameters. Two transmission levels were identified depending on the quantity of bacteria shed by infected individuals: (i) low-shedders with bacterial counts of resistant E. coli in the faeces between 5*10³ and 10⁶ CFU/g (β_L = 0.41 [0.27; 0.62]), (ii) high shedders with bacterial counts above 10⁶ CFU/g (β_H = 0.98 [0.59; 1.62]). Hence, transmission between animals could be pivotal in explaining the persistence of resistant bacteria within pig herds.  相似文献   

Evaluation of two derivatization reagents for the determination by LC-MS/MS of ammonia in cigarette mainstream smoke     

Mottier N  Jeanneret F 《Journal of agricultural and food chemistry》2011,59(1):92-97

Ammonia in cigarette mainstream smoke was quantified by LC-MS/MS after derivatization. Two different reagents, fluorescamine and dansyl chloride, were investigated, but only the latter gave stable derivatives; therefore, it was considered the most appropriate choice. Smoke samples were collected on a Cambridge filter pad followed by an impinger containing a solution of hydrochloric acid. Ammonia was then derivatized with a 18.5 mM solution of dansyl chloride in acetonitrile at 70 °C for 30 min in a vial with the internal standard, (15)ND(4)Cl. The resulting derivative was analyzed by LC-MS/MS detection with an atmospheric pressure chemical ionization (APCI) interface in the positive ionization mode using multiple-reaction monitoring (MRM). Good linearity was obtained in the concentration range of 0.02-1.65 μg/mL (r(2) ≥ 0.999), and the limit of detection (LOD) was established at 0.006 μg/mL. This method has the advantage of being sensitive, efficient, and reliable and is not hindered by interferences from the sample matrix. It should thus be considered a reference method of choice for the determination of ammonia in smoke.  相似文献   

Effects of syringomyelia on electrodiagnostic test results in Cavalier King Charles Spaniels     

Harcourt-Brown TR  Belshaw Z  Parker JE  Jeffery ND  Granger N 《American journal of veterinary research》2011,72(5):595-600

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Small intestinal strangulation caused by a mesodiverticular band and diverticulum on the mesenteric border of the small intestine in a horse     

Wefel S  Mendez-Angulo JL  Ernst NS 《The Canadian veterinary journal. La revue veterinaire canadienne》2011,52(8):884-887

A 4-year-old Quarter horse stallion was presented for acute abdominal pain. Exploratory celiotomy revealed a mesenteric diverticulum of the jejunum and mesodiverticular band that were associated with small intestinal strangulation. Resection and anastomosis were performed. A second celiotomy was performed due to adhesions. The horse recovered completely and returned to training.  相似文献