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三高农业与土壤和肥料有密切的关系。地力是作物产量的重要基础,要取得高产,就必须坚持不懈地培肥地力。综合地力、土壤中营养元素及有害或有毒物质的含量、肥料类型和施肥技术,都对农产品的品质有很大的影响。要提高农产品的产量和质量,就要因土种植,合理施肥。高产优质是经济效益的主要构成因素,因而,培肥地力、因土种植、合理施肥能提高经济效益。忽视土肥工作,将影响三高农业的发展。  相似文献   

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通过对原料林基地建设项目内容的分析 ,认为对“生态林”的界定标准 ,不能仅仅依据树木种类 ,还应考虑栽种的目的 ,这一观点在退耕还林的实际工作中具有一定的借鉴意义。  相似文献   

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McCauley SJ  Rowe L  Fortin MJ 《Ecology》2011,92(11):2043-2048
Nonconsumptive predator effects are widespread and include plasticity as well as general stress responses. Caged predators are often used to estimate nonconsumptive effects, and numerous studies have focused on the larval stages of animals with complex life cycles. However, few of these studies test whether nonconsumptive predator effects, including stress responses, are exclusively sublethal. Nor have they assessed whether these effects extend beyond the larval stage, affecting success during stressful life-history transitions such as metamorphosis. We conducted experiments with larvae of a dragonfly (Leucorrhinia intacta) that exhibits predator-induced plasticity to assess whether the mere presence of predators affects larval survivorship, metamorphosis, and adult body size. Larvae exposed to caged predators with no ability to attack them had higher levels of mortality. In the second experiment, larvae reared with caged predators had higher rates of metamorphic failure, but there was no effect on adult body size. Our results suggest that stress responses induced by exposure to predator cues increase the vulnerability of prey to other mortality factors, and that mere exposure to predators can result in significant increases in mortality.  相似文献   

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谈"动态对等"的缺陷   总被引:1,自引:0,他引:1  
美国著名翻译理论家Nida提出的"动态对等"原则是对翻译理论界的一大贡献.笔者在承认这个原则的同时,从它概念的几个关键词入手,指出这个概念中几个值得商榷的地方,认为它的理论基础不牢靠,并分析了它所忽视的翻译所涉及的几个要素,由此表明,翻译这种涉及到许多因素的复杂活动不能依靠一种理论来指导.  相似文献   

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周青 《生态环境》2007,16(5):1583-1584
环境问题本质是人的问题,具体表现于人口问题和人的德行问题。文章认为导致我们系列环境政策没有起到预想结果的原因在于我们"德行"中存在的认识误区,分析了这些认识误区;提出解决环境问题的根本途径是改造我们的"德行"并知道我们生活在地球"极限之内"。  相似文献   

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