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101.
Effects of traditional salt placement and strategically placed mineral mix supplements on cattle distribution in the Western Italian Alps 下载免费PDF全文
M. Pittarello M. Probo M. Lonati D. W. Bailey G. Lombardi 《Grass and Forage Science》2016,71(4):529-539
Effects of traditional salt placement (TS) and strategically placed mineral mix supplements (MMS) on cattle distribution were compared in the Italian Alps. Salt was placed within flat and herbaceous sites following the traditional method of farmers, whereas MMS blocks were placed on steep and shrub‐encroached sites within three large pastures (44 ha on average). Each TS and MMS site was paired with a control site, and eleven cows were tracked with GPS collars. Within 10 and 50 m of TS and MMS, treatment sites were used more than control sites (P < 0·05). No differences were detected (P > 0·05) in the number of visits by cows within 10 and 50 m of TS and MMS placements. No differences were detected in time spent within 10 m of TS and MMS placements, but cows spent more time (P < 0·05) within 50 m of TS. With either TS or MMS, cattle preferred areas with gentler terrain, higher forage pastoral value and closer to water (P < 0·001). When MMS was available cattle also preferred areas near MMS (P < 0·001). Shrub and herbaceous cover decreased near MMS placements (P < 0·05) from cattle grazing and trampling. Placement of MMS is a promising tool to enhance cattle distribution and potentially reduce shrub encroachment in rugged mountain pastures. 相似文献
102.
Paralytic shellfish poisoning (PSP), due to saxitoxin and related compounds, typically results from the consumption of filter-feeding molluscan shellfish that concentrate toxins from marine dinoflagellates. In addition to these microalgal sources, saxitoxin and related compounds, referred to in this review as STXs, are also produced in freshwater cyanobacteria and have been associated with calcareous red macroalgae. STXs are transferred and bioaccumulate throughout aquatic food webs, and can be vectored to terrestrial biota, including humans. Fisheries closures and human intoxications due to STXs have been documented in several non-traditional (i.e. non-filter-feeding) vectors. These include, but are not limited to, marine gastropods, both carnivorous and grazing, crustacea, and fish that acquire STXs through toxin transfer. Often due to spatial, temporal, or a species disconnection from the primary source of STXs (bloom forming dinoflagellates), monitoring and management of such non-traditional PSP vectors has been challenging. A brief literature review is provided for filter feeding (traditional) and non-filter feeding (non-traditional) vectors of STXs with specific reference to human effects. We include several case studies pertaining to management actions to prevent PSP, as well as food poisoning incidents from STX(s) accumulation in non-traditional PSP vectors. 相似文献
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M. G. Moraes N. J. Chatterton P. A. Harrison T. S. Filgueiras R. C. L. Figueiredo‐Ribeiro 《Grass and Forage Science》2013,68(1):165-177
Non‐structural carbohydrates (NSC) are the primary energy available for growth and dry‐mass production in forage grasses. They are also associated with tolerance to environmental stresses, including drought. Soluble carbohydrates, especially fructans of temperate forage grasses, have been extensively studied; however, little is known about NSC of tropical grasses. These plants are abundant in the Cerrado, a savanna‐like vegetation with a definite seasonality in rainfall distribution. Such an environment presents an ideal condition for the occurrence of fructans. However, the present analysis of carbohydrates in aerial parts of twenty‐four tropical grass species, mainly from the Panicoideae subfamily in the Cerrado, shows a distinctively different NSC profile when compared with temperate grasses. Free glucose and starch are common NSC found in most plant organs. However, free fructose and sucrose‐based oligosaccharides were only found in very low amounts. Sucrose was detected in higher amounts only in stems. A linear series of malto‐oligosaccharides was found in leaf blades, sheaths and stems of most of the Cerrado grasses, except for those from the Andropogoneae tribe. These results indicate a diversity of regulatory pathways of NSC metabolism in tropical forage grasses from the Cerrado. 相似文献
105.
油气管道运行寿命按其性质分为设计寿命、物理寿命和经济寿命,经济寿命的确定方法包括年均成本最小法和费用效益法,而费用效益法又包括年均利润最大法和总体收益分析法。年均成本最小法主要适用于成本中心和收入状况比较稳定或收入受计划控制而偏重成本控制的人为利润中心;费用效益法主要从运行效益的角度,根据经营者的承受程度和偏好,给出不同的经济运行参考年限。基于东北管网某管道的实际数据选用年均成本最小法和年均利润最大法,分别从全寿命周期和剩余寿命期两个视角,采用动态计算法,对该管道进行经济寿命测算,取得了具有参考价值的评估结果。 相似文献
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This paper puts forward a construction method based on ontology for the Pearl River Basin fish production,to facilitate the domain knowledge analysis and information retrieval.By converting the concept... 相似文献
109.
底栖鱼类对水田土壤微生物的扰动效应(摘要) 总被引:4,自引:0,他引:4
[目的]研究底栖鱼类泥鳅对水田土壤微生物(区系、生物量、生理群)的扰动效应。[方法]通过田间定位定量试验,采用平板表面涂抹法和稀释法进行分析。[结果]试验水田的土壤微生物区系组成中,细菌数量最多,其次是放线菌和真菌。养鱼水田的细菌、放线菌和真菌数量均高于对照水田,分别达到显著(P〈0.05)、极显著(P〈0.01)、极显著差异水平(P〈0.01)。养鱼水田的土壤微生物生物量C和N明显高于对照水田,均达到极显著差异水平(P〈0.01);养鱼水田的土壤微生物生物量P也高于对照水田,但并未达到显著差异水平(P〉0.05)。底栖鱼类促进了土壤固氮菌、纤维素分解菌、硝化细菌、硫化细菌和氨化细菌的生长,抑制了反硝化细菌和反硫化细菌的繁殖。[结论]底栖鱼类对水田土壤微生物区系、生物量和生理群具有重要影响,改善了土壤微生物的生存条件,提高了土壤肥力和生化活性,有助于增加土壤N、P、S等养分元素的供给能力和养分利用效率。 相似文献
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