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101.
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在金钱龟的人工养殖过程中,观察到部分个体发生了腐皮、肺炎、腹泻等疾病。通过对细菌的实验室诊断和生化特性鉴定,发现引起金钱龟腐皮和腹泻的病原体为嗜水气单胞菌,而肺炎则是由温度突变引起的感冒造成。因此,进一步研究了人工养殖条件下金钱龟的常见疾病与一些环境因子的关系。研究表明,温度差异对金钱龟的生理机能有显著的影响,而水质条件和养殖密度的调控也关系到金钱龟的健康生长,这也为金钱龟防治疾病及健康养殖模式提供一些参考依据。 相似文献
103.
《Scandinavian Journal of Forest Research》2012,27(6):555-573
Nitrogen (N) is the only nutrient that promotes forest growth when given individually. An extra stem growth of 15 m 3 ha -1 is obtained during a 10 yr period following an application of 150 kg N ha -1 . Larger growth increases have often been the result of more intensive N fertilization. Lime or wood ash give a minor growth stimulation on sites with a carbon (C) to N ratio below 30 in the humus layer, while the opposite effect prevails on N-poor sites. Nutrients given as soluble fertilizers are readily taken up by trees. Boron deficiency may be induced in northern Sweden after N fertilization or liming. The ground vegetation may be altered by single-shot N fertilization, but long-term effects occur only for intensive regimes. Lime or wood ash may modify the flora if soil pH is significantly altered: the change will be in response to N availability. Fruit-body production of mycorrhizal fungi is disfavoured by chronic N input, but also by lime or ash. However, the mycorrhizal structures on root tips are less affected. Faunistic studies are not common and those present are mostly devoted to soil fauna. A practical N dose of 150 kg N ha -1 has no clear effect, but higher doses may reduce the abundance in some groups. Hardened wood ash does not significantly affect the soil fauna. Lime favours snails and earthworms, while other groups are often disfavoured. The response of aquatic fauna to terrestrial treatments has hardly been studied. N fertilization generally results in insignificant effects on fish and benthic fauna. Lime and wood ash reduce the acidity of the topsoil, but practical doses (2-3 t ha -1 ) are too low to raise the alkalinity of runoff unless outflow areas are treated. N fertilizer use in forestry and N-free fertilizers lack effects on acidification. N fertilization may, however, be strongly acidifying if nitrification is induced and followed by nitrate leaching. N fertilization often results in increased long-term C retention in trees and soil, but does not promote significant N 2 O losses. N may temporarily reduce CH 4 oxidation in soil, but there are indications of a long-term opposite effect. Lime and poorly hardened wood ash may cause losses of C from N-rich soils. Only a few per cent of added N are leached to surface water following practical N fertilization, while N-free fertilizers do not induce N leaching. Soil incubations and soil-water studies suggest an increased risk for nitrate formation and leaching where lime or wood have been added to N-rich soils, but increased leaching to surface water has not been observed. Wood ash causes a temporal increase in bioavailability of cadmium (Cd). Other fertilizers may indirectly increase the availability of heavy metals. Wood ash may contain radioactive caesium 137Cs, but addition of such ash does not increase radioactivity in plants and soil. 相似文献
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105.
文章通过对东乌珠穆沁旗林地资源及其质量的分析,研究林地资源的发展对保护草原牧区生态环境的重要作用。 相似文献
106.
基于作物模型的温室环境管理系统设计与实现 总被引:3,自引:1,他引:2
为改进温室环境管理系统的性能,获取实时动态生成的决策信息,建立了基于作物模型的温室环境管理系统。在借鉴前人先进研究成果的基础上,通过实验建立了简化的温室番茄和黄瓜作物生长模型;其次,通过收集资料和专家经验建立了温室环境管理知识库;最后,应用农业环境实时监测数据,综合利用模型预测和知识推理建立了温室环境管理决策支持系统。通过实际运行表明,系统可实时动态输出室内温度、光照等参数的优化值及其它相关辅助决策信息,通过进一步完善可望取得更好的应用前景。 相似文献
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108.
Rebecca C. Bott Elizabeth A. Greene Katherine Koch Krishona L. Martinson Paul D. Siciliano Carey Williams Nathalie L. Trottier Amy Burk Ann Swinker 《Journal of Equine Veterinary Science》2013
Horses' physical and digestive well-being is often enhanced when allowed to graze on pastures. Furthermore, a well-managed pasture can contribute to economic viability. Grazing can however have deleterious effects on the environment if not properly managed. Although equine grazing, defecating, and ground trampling behavior is unique from that of other livestock species, pasture management practices are often based on those derived from cattle grazing. This review summarizes the current knowledge of impacts of equine grazing on pasture quality and environment and identifies gaps where further information is needed to formulate and recommend sustainable grazing methods specific to equine. 相似文献
109.
《Plant Production Science》2013,16(3):231-241
AbstractThe water crisis is threatening the sustainability of the irrigated rice system and food security in Asia. Our challenge is to develop novel technologies and production systems that allow rice production to be maintained or increased in the face of declining water availability. This paper introduces principles that govern technologies and systems for reducing water inputs and increasing water productivity, and assesses the opportunities of such technologies and systems at spatial scale levels from plant to field, to irrigation system, and to agro-ecological zones. We concluded that, while increasing the productivity of irrigated rice with transpired water may require breakthroughs in breeding, many technologies can reduce water inputs at the field level and increase field-level water productivity with respect to irrigation and total water inputs. Most of them, however, come at the cost of decreased yield. More rice with less water can only be achieved when water management is integrated with (i) germplasm selection and other crop and resource management practices to increase yield, and (ii) system-level management such that the water saved at the field level is used more effectively to irrigate previously un-irrigated or low-productivity lands. The amount of water that can be saved at the system level could be far less than assumed from computations of field-level water savings because there is already a high degree of recycling and conjunctive use of water in many rice areas. The impact of reducing water inputs for rice production on weeds, nutrients, sustainability, and environmental services of rice ecosystems warrants further investigation. 相似文献
110.