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苏丹草种子生产及市场浅析   总被引:3,自引:0,他引:3  
张鸿书  马福 《草业科学》1997,14(3):37-39
对当前苏丹草种子生产,市场出现的问题,提出了解决途径和方法,以法制化制约市场,保护生产者,经营者和消费者的合法权益。  相似文献   
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Calcareous grasslands, as extraordinarily species-rich and diverse habitats of northern and central Europe, need some management for their long-term conservation. Traditionally, they have been used as pastures, mainly with sheep, but goats are important, because they mainly browse and climb rocks. This study presents a comprehensive approach to the conservation of these sites, including the requirements of shepherds, which were obtained by a questionnaire, together with autecological information on the habitat requirements of species. Grazing is a central option, which has to be regulated in timing, intensity and spatial distribution, to gain optimum results. Nevertheless, local regulations must consider the requirements of the shepherds regarding infrastructure and social conditions, so that grazing remains practicable. Additionally, sheep-farming on conservation sites is presently unprofitable and therefore needs financial support. This support is supplied by state subsidies in Bavaria (Vertragsnaturschutzprogramm), and in the study area by a lamb-meat sales premium, which allows the shepherds to charge higher prices for lamb-meat produced under the premium regulations. The success of the overall strategy is only possible given a well adjusted interplay of influencing factors.  相似文献   
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To study the evolution of recombination rates in apes, we developed methodology to construct a fine-scale genetic map from high-throughput sequence data from 10 Western chimpanzees, Pan troglodytes verus. Compared to the human genetic map, broad-scale recombination rates tend to be conserved, but with exceptions, particularly in regions of chromosomal rearrangements and around the site of ancestral fusion in human chromosome 2. At fine scales, chimpanzee recombination is dominated by hotspots, which show no overlap with those of humans even though rates are similarly elevated around CpG islands and decreased within genes. The hotspot-specifying protein PRDM9 shows extensive variation among Western chimpanzees, and there is little evidence that any sequence motifs are enriched in hotspots. The contrasting locations of hotspots provide a natural experiment, which demonstrates the impact of recombination on base composition.  相似文献   
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Neospora caninum is a coccidian parasite identified as a major cause of abortion in cattle. A combined infection of N. caninum with another taxonomically related parasite of cattle, Besnoitia besnoiti can occur in geographical areas endemic for both species. Both infections are routinely diagnosed serologically, and incorrect diagnosis could occur if immunological cross-reactivity exists between the two parasites. To investigate the possible degree of cross-reactivity, we compared results obtained with two serological techniques, immunofluorescent antibody test (IFA), and Western blot analysis on known positive and negative sera. The test sera were derived from naturally infected cattle and from experimentally infected Mongolian gerbils. In IFA of bovine sera, no cross-reactvity was detected at the commonly used serum dilution cutoffs of 1:200 for N. caninum and 1:256 for B. besnoiti. However, at 1:64 dilution of both cattle and gerbil sera, anti-N. caninum sera reacted with B. besnoiti antigen in some individual samples. Anti-B. besnoiti serum did not react with N. caninum antigen at any dilution. This low level one directional cross-reactivity was confirmed by Western blot analysis. B. besnoiti antigen showed two immunoreactive bands when probed with anti-N. caninum serum, while no bands appeared when N. caninum antigen was probed with B. besnoiti antiserum. Immunization and challenge experiments in the highly susceptible Mongolian gerbil (Meriones unguiculatus) showed essentially no cross-protection between N. caninum and B. besnoiti.  相似文献   
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In 1985, the government of Indonesia declared an export ban on logs in order to promote the wood processing industry within the country. Furthermore, this policy was followed by a regulation that the concessionaires have to build their own industry, causing a great increase in wood industry. In the early period after the log export ban, the government found it to be successful and there were no significant problems. Unfortunately, after one decade, Indonesia’s forestry sector faced some serious problems,i.e. problems in raw material supply which was lower than the log demand level in the industry, deforestation issues, and ecological imbalance. The main objectives of this study are to identify the effects of the log export ban and to introduce some alternate measures.  相似文献   
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  1. Stingrays and guitarfish are globally threatened by overexploitation, particularly so in the Mediterranean Sea. Nevertheless, very little information is known about their ecology, behaviour, and taxonomy in the Mediterranean, and especially in the Levant, where water temperature, salinity, and the impact of invasive species are relatively high.
  2. Although it has been suggested that some species may aggregate in the Levant, this has not been formally documented and the scale of this phenomenon, the taxonomic composition, and the temporal dynamics are unknown.
  3. Visual surveys were conducted, which allowed the documentation of stingrays and guitarfish behaviour, and which was not available from data based on fishery catches. The census took place within a marine protected area over a period of 3 years.
  4. Altogether, we documented 675 batoid observations. One of the observed species is Endangered (Glaucostegus cemiculus) and one is Vulnerable (Dasyatis pastinaca), whereas the others are classed as Least Concern (Torpedo torpedo and Torpedo marmorata), Data Deficient (Taeniurops grabatus), non‐assessed within the Mediterranean (Dasyatis chrysonota), and Not Evaluated (Himantura uarnak). Results show clear seasonal patterns, with dense aggregations recorded during spring and early summer, when densities reached 85 observations per kilometre. In addition, there were clear indications of breeding behaviour in D. pastinaca and D. chrysonota, including the first recorded documentation of D. pastinaca courtship in the Mediterranean.
  5. Large seasonal stingrays and guitarfish aggregations in shallow waters have not, to our knowledge, been documented in the Mediterranean Sea previously. This highlights the importance of conserving shallow habitats as potential breeding grounds. As these sites are easily reached while both snorkelling and diving, the aggregation of these charismatic species can serve as potential ecotourism sites. Finally, this study shows the benefits of using simple visual census, as opposed to catch‐based methods, to record both the diversity and the behaviour of batoids.
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