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排序方式: 共有314条查询结果,搜索用时 15 毫秒
1.
Rural depopulation and recent landscape changes in a Mediterranean region: Consequences to the breeding avifauna 总被引:8,自引:0,他引:8
We studied the vegetational and avifaunistic changes following rural depopulation in an area covering 2,600 ha north of Montpellier
(Southern France). The study area is covered by a mosaic of Mediterranean habitats that includes cultivation, grasslands,
shrublands, and woodlands and is representative of the natural features present and of the human usage practiced so far in
this part of the Mediterranean.
We sampled the vegetation and the bird fauna in the same 193 census plots in 1978 and in 1992. At both the habitat and landscape
scales the cover of woody plants increased significantly. Open habitats tend to disappear. As a consequence the abundance
of open-habitat bird species decreased significantly whereas the abundance of forest birds increased significantly. These
changes favor a pool of forest species widespread in western Europe and reduce habitat availability for open habitat and shrubland
species. Many of the latter are Mediterranean species whose distribution in Western Europe could become reduced under current
landscape dynamics. Our observation of more woodlands and their typical birds and of less open habitats and their associated
avifauna is not consistent with the traditional worry shown by the public and the managers about the regression of forests
and woodlands in the Northern Mediterranean as a consequence of fire. 相似文献
2.
The utility, vehicle required, the time needed for assembly and relocation and the costs associated with six different rainfall simulators were studied. The results can be summarized as follows:
- 1 The simulator designed by Kainz & Eicher (1990) is the least expensive to operate. This simulator also has excellent experimental versatility. Its only restriction is a short slope length.
- 2 The rainfall simulator of Karl & Toldrian (1973) is also inexpensive to operate, but because of disadvantages such as low falling height, wind susceptibility, and the need for more workers than other simulators, it should be used mainly where other simulators are not practical (forests, steep slopes, or long slopes).
- 3 The rainfall simulator of Richter et al. (1988) has limited mobility in the field and is highly susceptible to wind drift. Moreover, its narrow plots do not cover a representative unit of a cultivated field.
- 4 The modified Swanson-type simulator (Auerswald, (1986) is suitable for large plots if a sufficient water supply is available.
- 5 The simulator of Kromer & Vöhringer (1988) has the highest fixed costs, but labour is used efficiently.
- 6 The simulator of Schmidt (1983) can only be considered for stationary use because of its long assembly time. Other disadvantages are narrow plot size and high wind susceptibility.
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5.
Brett Glencross Wayne Hawkins David Evans Neil Rutherford Peter McCafferty Ken Dods Max Karopoulos Chris Veitch Sofie Sipsas Bevan Buirchell 《Aquaculture (Amsterdam, Netherlands)》2008,277(3-4):220-230
Over a series of seven separate experiments 76 different lupin (Lupinus angustifolius) meals were assessed for their digestible dry matter, protein, amino acid and energy characteristics when fed to rainbow trout. Two reference diets (a common basal diet and a reference lupin meal) were also included in each experiment. Minimal variance in the digestibility parameters of both reference diets was observed among the experiments ensuring that there was a high degree of robustness in the across-experiment evaluations. Using simple and multiple-regression techniques, principal diet and ingredient composition factors affecting diet and ingredient digestibilities and ingredient digestible values were explored within the dataset. Using simple linear regression, it was shown that nitrogen digestibility of the lupin meals was negatively influenced by ingredient lignin content, but positively affected ingredient protein (N × 6.25) content. The energy digestibility of the lupin meals was positively affected by a range of compositional features including protein, sum of amino acids and negatively affected by carbohydrate content. The digestible nutrient and energy content of the meals reflected the combined effects of both ingredient digestibilities and ingredient composition. The digestible nitrogen content of the lupin meals was positively affected by protein (N × 6.25), sum of amino acids and energy content, but was negatively affected by lignin and carbohydrate content. The digestible sum of amino acids was also positively affected by protein, sum of amino acids, but only negatively affected by carbohydrate content, not lignin content. The digestible energy content of the lupin meals was also positively affected by protein, sum of amino acids and their own energy density, but only negatively affected by carbohydrate content. Multiple linear regression modelling supported that together ingredient protein and lignin content were the strongest predictors of digestible protein value, explaining close to 60% of the variability in this parameter. Discrete reassessment of these relationships using non-linear analysis methods provided a stronger interpretation of the ingredient composition effects. In recognition of this, a functional model including terms for ingredient protein and lignin content on the digestible protein value was defined. This study demonstrates that within one raw material type that not only does significant variability in the digestible value of the raw materials exist, but that it is possible to identify compositional features of that raw material that are intrinsically influencing their own digestible value. 相似文献
6.
Jari Setl Jukka Laitinen Jarno Virtanen Kaija Saarni Max Nielsen Asmo Honkanen 《Fisheries Research》2008,92(2-3):196-206
Freshwater fish species and Baltic salmon (Salmo salar) are important to small-scale fisheries in Finland and Sweden. The formerly local markets for these species have expanded as trade has been opened up to international competition. In this study we use cointegration analysis to test the spatial integration of freshwater fish markets in Finland and between Finland and Sweden. The analysed fish species are salmon, perch (Perca fluviatilis), pikeperch (Sander lucioperca), European whitefish (Goregonus lavaretus) and pike (Exos lucius), and the data covers ex-vessel prices from 1993 or 1995 to 2004. We found that the regional prices in Finland were cointegrated. This indicates that the prices are determined on a single market in Finland. Moreover, the study suggests that Finnish and Swedish markets in Baltic salmon, whitefish, pikeperch and perch were partially integrated, while integration of pike markets could not be found. The political implication is that an essential part of the local small-scale fisheries’ operational environment is determined outside the national borders. 相似文献
7.
Max Becker 《Plant foods for human nutrition (Dordrecht, Netherlands)》1968,15(1):48-64
Summary A review is given about publications of the last 30 years, concerning problems of high nitrate content of feeds. Nearly 10 areas of scientific work can be discerned. The most important of them have to do with: Analysis of nitrate and nitrite; danger of poisoning by feeds and water rich in nitrate; physiological and pathological consequences of high doses of nitrate or nitrite; reduction of nitrate (in the rumen and in the fermentation of plants) to nitrite, hydroxylamine and ammonia; behaviour of nitrate in the process of silage making; adverse effects upon the functions of the thyroid gland by nitrite and the disturbances of the availability of vitamin A and vitamin E by nitrate-nitrite.
Résumé On a donné un rapport sur les travaux scientifiques publiés dans les dernières trente années, concernant les problèmes d'une teneur haute en nitrate dans les fourrages. On peut discerner à peu près dix régions de travail scientifique. Les plus importantes sont: analyses du nitrate et du nitrite; le danger des intoxications par les fourrages et par l'eau, qui sont riches de nitrate; les conséquences physiologiques et pathologiques des doses hautes du nitrate ou du nitrite; la réduction du nitrate (dans le panse des ruminants et dans les fourrages en fermentation) au nitrite, au hydroxylamine et à l'ammonique; les réactions du nitrate pendant la préparation des silages; les influences défavorables aux fonctions de la glande thyroide par le nitrite; et les actions de déranger l'utilisation de la vitamine A et de la vitamine E par nitrate-nitrite.相似文献
8.
The bovine neutrophil: Structure and function in blood and milk 总被引:1,自引:0,他引:1
Migration of polymorphonuclear neutrophil leukocytes (PMN) into the mammary gland provide the first line of defense against invading mastitis pathogens. Bacteria release potent toxins that activate white blood cells and epithelial cells in the mammary gland to secrete cytokines that recruit PMN that function as phagocytes at the site of infection. While freshly migrated PMN are active phagocytes, continued exposure of PMN to inhibitory factors in milk such as fat globules and casein, leads to altered PMN morphology and reduced phagocytosis. In the course of phagocytosing and destroying invading pathogens, PMN release chemicals that not only kill the pathogens but that also cause injury to the delicate lining of the mammary gland. This will result in permanent scarring and reduced numbers of milk secretory cells. The life span of PMN is limited by the onset of apoptosis. To minimize damage to mammary tissue, PMN undergo a specialized process of programmed cell death known as apoptosis. Macrophages quickly engulf and phagocytose apoptotic PMN, thereby minimizing the release of PMN granular contents that are damaging to tissue. The PMN possess an array of cell surface receptors that allow them to adhere and migrate through endothelium and to recognize and phagocytose bacteria. One receptor found on phagocytes that is receiving considerable attention in the control of infections by Gram-negative bacteria is CD14. Binding of lipopolysaccharide (LPS) to membrane bound CD14 causes release of tumor necrosis factor-alpha and sepsis. Binding of LPS to soluble CD14 shed from CD14-bearing cells results in neutralization of LPS and rapid recruitment of PMN to the site of infection. Recent advances in the fields of genomics and proteomics should greatly enhance our understanding of the PMN role in controlling intramammary infections in ruminants. Further, manipulation of PMN, through either recombinant proteins such as soluble CD14 that enhance PMN response or agents that mediate PMN apoptosis, may serve as novel therapeutics for the treatment of mastitis. 相似文献
9.
Monfardini E Paape MJ Wang Y Capuco AV Husheem M Wood L Burvenich C 《Veterinary research》2002,33(3):271-281
Impaired polymorphonuclear neutrophil leukocyte (PMN) function around parturition has been associated with increased clinical mastitis in dairy cows. Rolling and attachment of PMN to the endothelium is the first step in the recruitment process and is accomplished by interaction between L-selectin on PMN and its ligand on endothelial cells. Furthermore, tyrosine phosphorylation is involved in the initiation of many PMN functions. The objective of this work was to determine changes in expression of L-selectin and tyrosine phosphorylation in the perinatal period. Eight clinically healthy Holstein cows were used as PMN donors at d-21, -14, -7,0 (calving), +1, +2, +7, +14, +28. Evaluation of L-selectin expression was carried out on activated and resting PMN. Anti-bovine L-selectin monoclonal antibody (MAB) and flow cytometric analysis were used to measure the percentage of PMN fluorescing and receptor expression (log mean fluorescent channel, LMFC). Activated and resting PMN showed similar trends in % PMN fluorescence and LM FC. The percentage of PMN fluorescing tended to decrease at parturition, followed by a significant increase at d +14 and +28 (P < 0.02). For LMFC a decrease was observed on d +1 followed by an increase through d +28 (P < 0.01). Protein tyrosine phosphorylation of lysates prepared from PMN isolated throughout the study was detected by electrophoresis and western blotting using anti-phosphotyrosine MAB. Several protein bands were tyrosine phosphorylated. Two of these bands (42-44 kDa and 90 kDa) varied in intensity over time. The intensity of the 42-44 kDa band gradually increased from d -7, peaked at d +7 (P < 0.03), and steadily decreased to d +28 (P < 0.02). Antibody to activated mitogen protein kinase reacted with the 42-44 kDa band. Reduced PMN function during the periparturient period could be related to reduced L-selectin adhesion molecules on the cell surface, and to modulation in the phosphorylation of functionally important molecules. 相似文献
10.
Max Dingler 《Forstwissenschaftliches Centralblatt》1930,52(7-8):318-323
Ohne Zusammenfassung 相似文献