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排序方式: 共有161条查询结果,搜索用时 15 毫秒
1.
Mouillot Florent Ratte Jean-Pierre Joffre Richard Moreno Jose Manuel Rambal Serge 《Landscape Ecology》2003,18(7):665-674
Based on recent needs to accurately understand fire regimes and post-fire vegetation resilience at a supra-level for carbon cycle studies, this article focusses on the coupled history of fire and vegetation pattern for 40 years on a fire-prone area in central Corsica (France). This area has been submitted since the beginning of the 20th century to land abandonment and the remaining land management has been largely controlled by frequent fires. Our objectives were to rebuild vegetation and fire maps in order to determine the factors which have driven the spatial and temporal distribution of fires on the area, what were the feed backs on the vegetation dynamics, and the long-term consequences of this inter-relationship. The results show a stable but high frequency of small fires, coupled with forest expansion over the study period. The results particularly illustrate the spatial distribution of fires according to topography and vegetation, leading to a strong contrast between areas never burnt and areas which have been burnt up to 7 times. Fires, when occuring, affect on average 9 to 12% of the S, SE and SW facing slopes (compared to only 2 to 5% for the N facing slopes), spread recurrently over ridge tops, affect all the vegetation types but reburn preferentially shrublands and grasslands. As these fire-proning parameters have also been shown to decrease the regeneration capacity of forests, this study highlights the needs in spatial studies (both in terms of fire spread and vegetation dynamic) to accurately apprehend vegetation dynamic and functionning in fire-prone areas.This revised version was published online in May 2005 with corrections to the Cover Date. 相似文献
2.
Joo Carlos de Moraes S Lucien Sguy Florent Tivet Rattan Lal Serge Bouzinac Paulo Rogrio Borszowskei Clever Briedis Josiane Burkner dos Santos Daiani da Cruz Hartman Clayton Giani Bertoloni Jadir Rosa Theodor Friedrich 《Land Degradation \u0026amp; Development》2015,26(6):531-543
The continuous use of plowing for grain production has been the principal cause of soil degradation. This project was formulated on the hypothesis that the intensification of cropping systems by increasing biomass‐C input and its biodiversity under no‐till (NT) drives soil restoration of degraded agro‐ecosystem. The present study conducted at subtropical [Ponta Grossa (PG) site] and tropical regions [Lucas do Rio Verde, MT (LRV) site] in Brazil aimed to (i) assess the impact of the continuous plow‐based conventional tillage (CT) on soil organic carbon (SOC) stock vis‐à‐vis native vegetation (NV) as baseline; (ii) compare SOC balance among CT, NT cropping systems, and NV; and (iii) evaluate the redistribution of SOC stock in soil profile in relation to soil resilience. The continuous CT decreased the SOC stock by 0·58 and 0·67 Mg C ha−1 y−1 in the 0‐ to 20‐cm depth at the PG and LRV sites, respectively, and the rate of SOC sequestration was 0·59 for the PG site and ranged from 0·48 to 1·30 Mg C ha−1 y−1 for the LRV site. The fraction of C input by crop residues converted into SOC stock was ~14·2% at the PG site and ~20·5% at the LRV site. The SOC resilience index ranged from 0·29 to 0·79, and it increased with the increase in the C input among the NT systems and the SOC sequestration rates at the LRV site. These data support the hypothesis that NT cropping systems with high C input have a large potential to reverse the process of soil degradation and SOC decline. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
3.
Clinical and in vitro efficacy of amoxicillin against bacteria associated with feline skin wounds and abscesses 总被引:1,自引:0,他引:1
Roy J Messier S Labrecque O Cox WR 《The Canadian veterinary journal. La revue veterinaire canadienne》2007,48(6):607-611
A clinical trial involving 122 cats with infected skin wounds or abscesses presented to 10 veterinary clinics was conducted to evaluate the efficacy of 2 oral amoxicillin drug products (a paste and a suspension). A 2nd objective of the study was to identify bacteria involved in such infections and verify their in vitro sensitivity to amoxicillin. Samples of wound exudate were harvested at the time of presentation and submitted for aerobic and anaerobic culture. The sensitivity to amoxicillin of isolates thought to be infecting agents was tested, using a standard minimum inhibitory concentration method. Pasteuralla multocida and obligate anaerobes of the genera Prevotella, Fusobacterium, and Porphyromonas were the most frequently isolated pathogens. Overall, their in vitro susceptibility to amoxicillin was very good. Both drug products were clinically efficacious with a global success rate of 95.1% for cats administered oral amoxicillin at 11-22 mg/kg bodyweight (mean 13.8 mg/kg bodyweight) twice daily for 7 to 10 days. 相似文献
4.
Rezzi S Giani I Héberger K Axelson DE Moretti VM Reniero F Guillou C 《Journal of agricultural and food chemistry》2007,55(24):9963-9968
The combination of (1)H NMR fingerprinting of lipids from gilthead sea bream (Sparus aurata) with nonsupervised and supervised multivariate analysis was applied to differentiate wild and farmed fish and to classify farmed specimen according to their areas of production belonging to the Mediterranean basin. Principal component analysis (PCA) applied on processed (1)H NMR profiles made a clear distinction between wild and farmed samples. Linear discriminant analysis (LDA) allowed classification of samples according to the geographic origin, as well as for the wild and farmed status using both PCA scores and NMR data as variables. Variable selection for LDA was achieved with forward selection (stepwise) with a predefined 5% error level. The methods allowed the classification of 100% of the samples according to their wild and farmed status and 85-97% to geographic origin. Probabilistic neural network (PNN) analyses provided complementary means for the successful discrimination among classes investigated. 相似文献
5.
It has been shown that Escherichia coli isolates from lesions of cellulitis belong to a limited number of clonal groups distinct from those of isolates found in the environment of these birds. In this study, different in vitro methods were used to evaluate adherence properties of E. coli isolates from cellulitis lesions and environments of high- and low-cellulitis prevalence broiler flocks. One hundred isolates were tested by hemagglutination. Adherence to frozen sections of chicken skin and binding to soluble fibronectin were examined for 40 of these 100 isolates by immunofluorescence and by immunocytofluorometry, respectively. Localization of bacterial adherence to skin tissues was confirmed by immunohistochemistry. It was demonstrated that O78:K80 isolates from cellulitis lesions adhered to skin sections to a much greater extent in deeper than in superficial tissue layers. A greater bacterial adherence following growth in TSB at 37 C was demonstrated for isolates from flocks with high prevalence of cellulitis than for isolates from flocks with low prevalence of cellulitis. MANOVA analysis results showed a significant difference between superficial and deep tissue layers only for one set of isolates from flocks with high prevalence of cellulitis. Hemagglutinating activity was variable among the O78:K80 isolates obtained from flocks with high prevalence of cellulitis. The results obtained for some O78:K80 isolates following growth in TSB suggest a role for type 1 fimbriae or F1 in adherence to skin sections. This was reinforced by the finding that adherence was inhibited by D-mannose. Poultry E. coli isolates that express F1 had no affinity for soluble fibronectin, although localization of the adherence in skin sections suggested a role for extracellular matrix components such as collagen and insoluble fibronectin. 相似文献
6.
Reproductive phenology was observed over three years in a Eucalyptus grandis seed orchard in Madagascar to determine the impact of geographic differences of parental selections on the expected genetic composition of seed crops. Pollen flow (observed pollen cloud) was deduced from a paternity assignment based on sampling from one year’s seed production. The two approaches were used to verify whether knowledge of phenology is sufficient to predict the genetic quality of the seeds collected. Despite the high flowering level, with a constant cycle over three years, the results demonstrated wide reproductive phenological differences associated with the parents’ origin, suggesting putative pollination disequilibrium. From both observed and expected pollen clouds, the results showed preferential mating among different provenances, which has consequences for seed crop composition. Phenological observations, which can be made inexpensively, can be used to promote methods of effective seed orchard management in order to improve the genetic quality of seeds. 相似文献
7.
8.
Rodents are recognized reservoir hosts for many human zoonotic pathogens. The current trends resulting from anthropocene defaunation suggest that in the future they, along with other small mammals, are likely to become the dominant mammals in almost all human‐modified environments. Recent intricate studies on bat‐borne emerging diseases have highlighted that many gaps exist in our understanding of the zoonotic transmission of rodent‐borne pathogens. This has emphasized the need for scientists interested in rodent‐borne diseases to integrate rodent ecology into their analysis of rodent‐borne pathogen transmission in order to identify in more detail the mechanisms of spillover and chains of transmission. Further studies are required to better understand the true impact of rodent abundance and the importance of pathogen sharing and circulation in multi‐host– multi‐pathogen communities. We also need to explore in more depth the roles of generalist and abundant species as the potential links between pathogen‐sharing, co‐infections and disease transmission. 相似文献
9.
Eliane Gonzalez-Rodriguez Serge Y. Maestrini 《Aquaculture (Amsterdam, Netherlands)》1984,36(3):245-256
Three Brazilian and 9 French agricultural fertilizers were compared with Conway mixture, as nutrient enrichment for supporting the growth of 16 marine algae. Fertilizers containing only nitrogen and phosphorus appeared to be suitable. However, a few algae grew better in all-nutrient-enriched Conway medium. Addition of chelators did not generate better growth. Matrix-free fertilizers were found more convenient in use. A table is given to show the cheapest and/or best nutrient enrichment for each algal strain tested. 相似文献
10.