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1.
通过测坑定位试验,研究了3种施肥处理下稻田土壤微生物多样性变化。试验结果表明,有机肥能提高土壤微生物的丰富度和多样性。施肥后,稻田上层土壤的土壤微生物群落结构发生了明显的改变。有机肥处理的土壤DNA丰富度最大,为19;无机肥处理的最小,为14。3种施肥处理的DNA序列Shannon-Weaver指数分别为:混施肥处理1.85,有机肥处理2.30和无机肥处理1.60,均匀度指数分别为:混施肥处理0.73,有机肥处理0.82和无机肥处理0.64。上层土壤中,无机肥处理和混施肥处理的微生物多样性相似系数为79%,而施用有机肥的处理与混施肥处理、无机肥处理的相似系数为62%,这表明施用有机肥能明显改变稻田土壤微生物的种群结构。下层土壤各处理仍然具有较高的相似性。 相似文献
2.
不同施肥处理对茭白田土壤中氮素变化动态的影响 总被引：2，自引：0，他引：2
为探索茭白田氮素的流失规律,减少水体富营养化,本文以测坑定位试验为基础,研究了在3种不同施肥处理下黄浦江上游地区茭白田水中氮素变化动态。结果表明。茭白田水中的氮素分布和其它水田作物相类似。各处理茭白田坑面水中氮素形态以NH4^＋-N为主;渗漏水中流失的氮素主要以NO3^--N为主,分别占总氮的化肥处理73．44％。混合肥处理67．62％和有机肥处理53.31％。由剖面水中氮素分布可知,实际生产所施用的氮肥用量远远超过茭白生长所需。通过减少化肥用量而改施有机肥可减少施肥过后由暴雨引起的氮素径流流失和整个施肥期30％的地下水渗漏流失,同时对茭白产量没有显著影响。 相似文献
3.
海冰水灌溉配合农艺措施对棉田土壤水盐动态的影响 总被引：1，自引：0，他引：1
采用海冰水(含盐量3‰)灌溉,结合4种施肥措施(无机肥、有机肥与无机肥配施、土壤调理剂与无机肥配施和不施肥处理),研究海冰水灌溉配合农艺措施对土壤水分和盐分动态的影响。2007年-2008年结果表明:苗期和花期灌水后海冰水处理的土壤含水率均显著高于井水处理,尤其灌溉后播种前期0～40cm土层含水量差异显著;井水灌溉施加液膜处理的土壤含水率较未处理的显著提高。海冰水灌溉土壤1m土体脱盐率达40%。连续两年试验,两种灌溉水处理并配合不同农艺措施条件下均可有效淋洗土壤中盐分。2007年海冰水灌溉下,土壤调理剂与无机肥配施处理和有机肥与无机肥配施处理的小区0～40cm土壤脱盐率显著高于无机肥单施的处理(约53%～55%)。本试验研究得出,使用3‰的海冰水加液膜处理后灌溉棉田,并配合土壤调理剂与无机肥配施或有机肥与无机肥配施,能够加快灌溉后水分入渗和土壤盐分的淋洗。 相似文献
4.
海洋表层沉积物中的无机氮在扰动情况下的行为特征 总被引：1，自引：0，他引：1
本文模拟了海洋表层沉积物再悬浮对海水中NH+4-N、NＯ-3-N浓度的贡献。通过实验，观察到海水中NH+4-N的浓度与沉积物和海水的混合比例成负相关性。在不同震荡速率的试验中，60rpm震荡速率下的NH+4-N浓度逐渐降低到三种速率中的最低,120rpm震荡速率下的NH+4-N浓度升至最高。所选海区的沉积物在再悬浮过程中细粒径沉积物对上层水体NH+4-N的贡献最大，其次是中粒径沉积物、粗粒径沉积物。海水中NＯ-3-N的浓度与混合比例和震荡速率均成负相关性。粗、细粒径沉积物在试验过程中对水体的贡献具有很强的一致性，中粒径沉积物对水体的贡献要大于粗、细粒径沉积物的贡献。再悬浮过程中沉积物对海水中NＯ-3-N、NH+4-N的贡献主要来源于KCl浸取态氮和HAc-NaAc浸取态氮。 相似文献
5.
生产建设项目建设过程中会产生大量的弃土,弃土养分极度缺乏、结构紊乱。为了给黄土高原沟壑区弃土场培肥提供一定的技术依据,试验在黄土高原陕西省长武农业生态试验站模拟弃土场进行。试验选取白三叶、草木樨、紫穗槐、柠条、黑麦草5种植物,探究在不同施肥处理下各植物小区0~10 cm、10~20 cm土层的养分含量。设施有机肥(羊粪),施肥量为30000 kg/hm~2;施秸秆,施肥量为9000 kg/hm~2,以及不施肥三种施肥处理,探寻植物在单播、混播模式下对弃土场的土壤培肥效果。黑麦草+白三叶在三种处理下的土壤肥力均较高,培肥效果较好。 相似文献
6.
为了研究大型海藻对海水养殖水体的净化效果,选取羊栖菜(Sargassum fusiforme)、细基江蓠(Gracilaria tenuistipitata)和裙带菜(Undaria pinnatifida)等3种大型海藻为研究对象,考察了3种大型海藻在72h内对海水养殖水体中无机氮和活性磷酸盐的净化效果。结果显示,3种大型海藻对海水养殖水体中无机氮和活性磷酸盐均有较好的去除效果。羊栖菜、细基江蓠、裙带菜对养殖水体中NH+4-N的最大去除率分别为79.87%、83.96%、75.62%;对养殖水体中NO-3-N的最大去除率分别为65.99%、72.22%、59.11%;对养殖水体中PO3-4-P的最大去除率分别为59.61%、84.56%、67.37%。其中细基江蓠对养殖水体中NH+4-N、NO-3-N及PO3—4P的净化去除效果最好。 相似文献
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8.
施用不同有机肥对盆栽大豆土壤可溶性有机质和无机氮含量的影响 总被引：1，自引：0，他引：1
通过大豆的盆栽试验,研究了施用两种常见的有机肥——腐殖酸有机肥和甲壳素有机肥后紫色土可溶性有机碳、氮的变化特征。试验结果表明:与未施肥处理相比,在整个大豆生长期间,施用腐殖酸和甲壳素有机肥处理均显著增加了土壤硝态氮含量;只有施用腐殖酸有机肥处理,在发芽期和出枝期,土壤铵态氮含量显著高于未施肥处理,而两种有机肥都是在结荚期显著低于未施肥处理。与未施肥处理相比,在整个生育期,除施腐殖酸有机肥的开花期和结荚期,施用腐殖酸和甲壳素有机肥处理均显著提高了土壤可溶性有机碳含量;除出枝期,施用有机肥处理均显著降低了土壤可溶性有机氮含量。 相似文献
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10.
《资源科学》2017,(1)
气候变暖已成为全球关注的热点话题,农业温室气体是气候暖化的重要排放源。目前许多学者研究了不同施肥措施下温室气体排放的特征,但实验结果之间存在一定的差异。为了综合评价区域内不同施肥措施(单施无机氮(N)、无机氮磷钾(NPK)和有机无机配施(OF))下土壤温室气体排放的特征及其净减排潜力,本文基于长江中下游地区40篇关于施肥对稻田温室气体CH_4和N_2O排放的文献,筛选出339组样本数据,采用Meta分析方法从施肥类型、施肥时间和施肥水平三个方面定量研究了3种施肥措施对稻田CH_4和N_2O排放的影响,并在前期研究的基础上,估算了各个施肥处理下的综合增温潜势、净增温潜势以及温室气体排放强度。结果表明:N、NPK和OF处理下CH_4周年排放的效应值分别为0.24、0.27和0.63,N_2O周年排放的效应值分别为1.25、1.26和1.41。随着施肥次数的增加,N、NPK和OF处理下温室气体排放的效应值均逐渐增大;随着施肥量的增加,N处理表现为增加的趋势,NPK处理表现为减少的趋势,OF处理表现为先增后减的趋势。对于3种施肥处理下的净增温潜势大小为OFNPKN,其中CH_4排放对温室气体的贡献最大;3种施肥处理下的温室气体排放强度大小为OFNPKN。从粮食增产和温室气体减排两方面综合考虑,施用氮磷钾(NPK)是长江中下游地区稻田较适宜的施肥方式。 相似文献
11.
A research group led by Prof. ZHAI Qiwei from the Institute for Nutritional Sciences under the CAS Shanghai Institutes for Biological Sciences has discovered that even relatively low doses of resveratrol-a chemical found in the skins of red grapes in red wine-can improve the sensitivity of mice to the hormone insulin according to a report in the October issue of Cell Metabolism.…… 《中国科学院院刊(英文版)》2008,22(1):14-15
Aresearch group led by Prof. ZHAI Qiwei from the Institute for Nutritional Sciences under the CAS Shanghai Institutes for Biological Sciences has discovered that even relatively low doses of resveratrol--a chemical found in the skins of red grapes and in red wine--can improve the sensitivity of mice to the hormone insulin, according to a report in the October,2007 issue of Cell Metabolism. As insulin resistance is often characterized as the most critical factor contributing to the development of Type 2 diabetes, the findings“provide a potential new therapeutic approach for preventing or treating” both conditions, the researchers said. 相似文献
12.
《中国科学院院刊(英文版)》2008,22(1):2-3
CAS should stick to the principle of rendering service to, and giving impetus for, the development of China＇s science enterprise by making S＆T innovations, said CAS President LU Yongxiang. The CAS president made the remarks in a recent talk to communicate the gist of the winter session of the Party＇s Leading-member Group at CAS, which was held from 7 to 11 January in Beijing. 相似文献
13.
Marjorie Armstrong-Stassen Margaret Landstrom Ramona Lumpkin 《The Information Society》1998,14(2):153-164
This study examined how students who had no prior experience with videoconferencing would react to the use of videoconferencing as an instructional medium. Students enrolled in seven different courses completed a questionnaire at the beginning of the semester and again at the end of the semester. Students at the origination and remote sites did not differ in their reactions toward videoconferencing but there was a significant difference for gender. Women reacted less favorably to videoconferencing. Compared to the beginning of the semester, students reported significantly less positive attitudes toward taking a course through videoconferencing at the end of the semester. There were no significant differences in students' attitudes toward videoconferencing across courses at the beginning of the semester but there were significant differences across the courses at the end of the semester. The results suggest the need for better preparation for both students and instructors. 相似文献
14.
《中国科学院院刊(英文版)》2008,22(1)
With great care, Dr. ZHOU Zhonghe takes out a package wrapped by cotton tissue from a drawer and says: "This is the gem of our collections: the fossil of a bird that lived 125 million years ago!" Then, pointing at a tiny mound, he explains: "Look, this is the claw and that is the head. It was in the egg shell and ready to hatch ... The species fell into a family of waterside inhabitants." 相似文献
15.
A joint study by Prof. ZHANG Zhibin from the CAS Institute of Zoology his co-workers from Norway US Swiss have indicated that historical outbreaks of migratory locusts in China were associated with cold spells suggesting that China's projected climate warming could decrease the pest's numbers. The study was published in Proceedings of the National Academy of Sciences on September .…… 《中国科学院院刊(英文版)》2008,22(1):6-7
Ajoint study by Prof. ZHANG Zhibin from the CAS Institute of Zoology and his co-workers from Norway, US and Swiss have indicated that historical outbreaks of migratory locusts in China were associated with cold spells, suggesting that China＇s projected climate warming could decrease the pest＇s numbers. The study was published in Proceedings of theNational Academy of Sciences on 17 September, 2007. 相似文献
16.
Caroline Haythornthwaite 《The Information Society》2001,17(3):211-226
A computer-mediated group is a complex entity whose members exchange many types of information via multiple means of communication in pursuit of goals specific to their environment. Over time, they coordinate technical features of media with locally enacted use to achieve a viable working arrangement. To explore this complex interaction, a case study is presented of the social networks of interactions and media use among members of a class of computer-supported distance learners. Results show how group structures associated with project teams dominated who communicated with whom, about what, and via which media over the term, and how media came to occupy their own communication niches: Webboard for diffuse class-wide communication; Internet Relay Chat more to named others but still for general communication across the class; and e-mail primarily for intrateam communication. Face-to-face interaction, occurring only during a short on-campus session, appears to have had a catalytic effect on social and emotional exchanges. Results suggest the need to structure exchanges to balance class-wide sharing of ideas with subgroup interactions that facilitate project completion, and to provide media that support these two modes of interaction. 相似文献
17.
Active biological molecules functional structures can be fabricated into a bio-mimetic system by using molecular assembly method. Such materials can be used for the drug delivery disease diagnosis therapy new nanodevice construction.…… 《中国科学院院刊(英文版)》2008,22(1):22-22
Active biological molecules and functional structures can be fabricated into a bio-mimetic system by using molecular assembly method. Such materials can be used for the drug delivery, disease diagnosis and therapy, and new nanodevice construction. 相似文献
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Electronic data interchange (EDI) provides means for interorganizational communication, creates network externalities, requires an advanced information technology (IT) infrastructure, and relies on standards. In the diffusion of such innovations, institutional involvement is imperative. Such institutions contain governmental agencies, national and global standardization organizations, local government, and nonprofit private organizations like industry associations. The last type of organizations we call intermediating institutions. They intermediate or coordinate ("inscribe") the activities of a group of would-be adopters. Unfortunately, little is known of how these organizations shape the EDI diffusion trajectory. In this article we examine one specific type of intermediating organizations?industry associations?and how they advanced the EDI diffusion process in the grocery sectors of Hong Kong, Denmark and Finland. We identify six institutional measures, placed into a matrix formed by the mode of involvement (influence vs. regulation) and the type of diffusion force (supply push vs. demand pull), that can be mobilized to further the EDI diffusion. Industry associations were found to be active users of all these measures to varying degrees. Their role was critical especially in knowledge building, knowledge deployment, and standard setting. Furthermore, institutional involvement varied due to policy and cultural contingencies and power dependencies. 相似文献
19.
Leah A. Lievrouw 《The Information Society》2000,16(2):155-159
This essay focuses on universal service and the Internet as means to support social and political participation. The emphasis on access to telecommunications systems in conventional approaches to universal service is contrasted with access to content. A model of the information environment is described that accounts for the roles of content and conduit, both of which are necessary conditions to achieve true access. A method is outlined for employing information indicators to observe or measure the information environment. 相似文献
20.
Puay Tang 《The Information Society》1998,14(1):19-31
The increasing prospects of digital piracy has prompted the perceived need by electronic publishers to adopt technical systems of protection, and governments to reform their copyright laws. This article is a preliminary study of the management of intellectual property by electronic publishers, defined as those involved in the production of online databases, and CD-ROMs. It focuses on three main issues: (1) how electronic publishers view the increasing threat of piracy; (2) the methods of protection employed to protect intellectual property in digital format; and (3) the importance of technological protection of intellectual property in electronic publications. The analysis is based on a sample of 23 UK electronic publishers. The interviews revealed an interesting assortment of protection methods and did not show that technological protection was a preferred way. Instead, the means of protection, in addition to copyright law, comprised niche markets, pricing, trust, bad publicity, and nontechnical and technical means. 相似文献