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1.
细化中小尺度农业系统碳足迹的研究既可为当地低碳农业的发展提供科学依据,也可为大尺度农业系统的碳足迹研究提供基本素材。本论文基于投入产出视角,以位于农牧交错带的宁夏盐池县为案例区,通过分析种植业碳排放源,细化碳吸收的各类作物,选定主要投入要素的碳排放系数和各种作物的碳吸收率,重点分析了1995-2012年研究区农作物的碳吸收对农业化学物质及能源投入碳排放的消纳情况。结果表明：盐池县种植业的碳平衡处于碳生态盈余状态,净碳汇稳步上升,年平均增长率达13.31%。碳排放、碳吸收和碳足迹在1995-2000年、2000-2007年和2008-2012年3个时段存在显著性差异。根据相应时段的变异系数和当地生态退耕政策的影响,将碳足迹变化分为3个时期,即不稳定期1995-2000年、较稳定期2000-2007年和稳定期2008-2012年。然而,上述碳生态盈余状态并不能掩饰农业化学物质和能源投入不断增加所带来的不可再生资源年损耗的增加和农业面源污染潜在风险的加剧。 相似文献
2.
【目的】农业碳排放问题对于碳达峰碳中和目标实现具有重要意义,农地流转是重大农业变革,对农业碳排放具有显著作用,然而现有研究未深入探索农地流转对农业碳排放的影响,影响了农业碳减排工作的进一步推进。【方法】本文在理论探讨基础上结合2005—2020年中国30个省份面板数据,综合利用双固定效应回归模型、工具变量模型、中介效应模型、空间计量模型,在严格检验基础上实证分析了农地流转对农业碳排放的影响效应、中介路径及其空间特性。【结果】①农地流转对农业碳排放产生显著正向影响,即农地流转面积扩大会促进农业碳排放增加;②农业经营规模在农地流转促进农业碳排放增加过程中发挥部分中介效应,农地流转能通过提升农业经营规模进而增加农业碳排放;③考虑空间效应时,农地流转对本地区农业碳排放产生显著正向影响,对邻近地区农业碳排放产生显著负向影响,农业经营规模在农地流转对本地区农业碳排放的影响过程中发挥部分中介效应。【结论】农地流转对农业碳排放存在显著影响,农地流转推进过程应重视农业碳排放问题。 相似文献
3.
中国农业碳排放研究:测算、时空比较及脱钩效应 总被引：31，自引：1，他引：30
本研究基于农地利用、稻田、牲畜肠道发酵和粪便管理等四方面16类主要碳源,测算了我国1995年-2010年期间以及31个省(市、区)2010年的农业碳排放量。结果表明:①2010年我国农业碳排放总量为28673.23万t,较1995年增加了12.31%。其中,农地利用、稻田、肠道发酵和粪便管理所导致的碳排放量分别占农业碳排总量的34.29%、42.48%、17.77%和5.46%;分阶段来看,呈现较为明显的"上升-下降-上升"的三阶段变化特征;②横向来看,区域差异明显:农业碳排放总量,排在前10位的地区占全国农业总排放的59.61%,而排在后10位的地区仅占全国8.33%,传统农业大省尤其粮食主产省区是我国农业碳排放的主要来源地;基于碳排放比重差异,将31个地区划分为了稻田主导型、农地利用主导型、牲畜肠道发酵主导型、复合因素主导型等四种不同结构类型;农业碳排放强度,总体呈现出西高东低的特征,即西部>中部>东部。在此基础上,运用Tapio脱钩模型对我国农业碳排放与农业经济发展间的脱钩关系进行了分析,发现以弱脱钩和强脱钩为主,说明近年来我国在农业碳减排方面取得了一定成效。 相似文献
4.
检索并下载美国科技情报研究所(ISI)的Web of Science网络平台的文献数据进行计量分析,通过可视化的科学知识图谱和文献共被引网络中的节点突现率指标,探测国际科学合作领域演进的研究前沿。2000年以前的一段时间,国际上科学合作领域的研究前沿问题主要包括:对科学合作的起源、基本概念界定等,科学合作网络的结构、测度与网络模型,国际科学合作的测度和影响因素,医药和卫生领域的科学合作问题等;另一方面,2000年以后,科学合作领域研究前沿主要包括科学合作网络、国际科学合作、社会网络方法与技术、文献计量指标在科学合作研究中的应用等问题。 相似文献
5.
河北省曲周县农田生态系统碳循环及碳效率研究 总被引：4，自引：0，他引：4
农田生态系统在全球碳循环中具有突出地位,研究农田生态系统碳循环过程、掌握地区碳收支情况,对挖掘农田多功能性、发展低碳农业具有重要意义,同时为制定农业生态补偿提供依据。本文综合分析农田生态系统碳循环过程,并根据实际情况修正核算了碳排放系数,从碳输入、碳输出、固碳三个过程对曲周县农田生态系统碳源和碳汇以及碳效率进行研究。结果表明,2011年曲周县农田生态系统碳平衡值为-3.30万t,当年可固定碳17.61万t。土壤呼吸、农用机械以及氮肥、磷肥的使用是造成碳排的主要因素。各乡镇农田生态系统碳源和碳汇情况有所差异,曲周镇等乡镇由于高投入低产出导致当年系统为碳源,而候村镇、河南疃镇等乡镇由于低投入、高产出导致当年系统为碳汇。曲周县农田生态系统虽整体表现为碳源,但仍具有较强的碳汇能力以及较高的碳效率,在一定程度上可弥补碳排放对环境造成的影响。 相似文献
6.
低碳农业与农作物碳足迹核算研究述评 总被引：4，自引：0，他引：4
持续提高农业产量、提高土壤生产力、降低环境污染的低碳农业是21世纪发展的主旋律,碳足迹评价方法是支撑低碳农业技术转型、碳交易、碳标签等管理措施的基础。本研究收集了水稻、小麦、玉米3种作物的22个研究结果,发现碳足迹仍有很大的不确定性,目前国内外尚没有建立统一的碳足迹核算方法体系,导致同一作物碳足迹相差达十几倍,例如水稻碳足迹从1895 kgce/hm2（ce：CO2equal,即二氧化碳等当量）,到11 811kgce/hm2,而小麦和玉米的净排放却出现相反的两个结果,即固碳（净碳排放为负值）和排放（净碳排放为正值）。分析表明,主要问题在于模型边界、温室气体种类、数据获取途径、量化单位等方面不一致,因此需要重构作物生产碳足迹研究方法。本文提出了用生命周期方法量化农作物生产碳足迹的理论模型,提出以农业投入品上游排放、农田生产排放、以及土壤固碳为边界的生命循环为边界,量化全生命链条中的CO2、CH4、N2O等直接排放因子以及NH3和NO3-等间接排放因子,通过大样本数据建立关键排放因子的量化模型,实现区域性碳足迹的定量化分析。 相似文献
7.
研究控排企业的林业碳汇需求,对于引导企业科学选择减排路径与有效发挥林业碳汇抵消企业碳排放的作用而言至关重要。以控排企业为对象,将其对林业碳汇抵消碳排放机制的认知与响应统一纳入贝叶斯网络,从而揭示控排企业林业碳汇需求机理,并从林业碳汇减排量、抵消比例、价格决定、风险承担等多个维度进行仿真。研究表明：林业碳汇需求是控排企业自身及环境因素复杂作用的动态过程;尽管在森林增汇与减排方面表现出较高的认知与认可,但面对当前充裕的碳配额及不明确的林业碳汇市场预期,控排企业期望林业碳汇占CCER的比例及购买林业碳汇的意愿并不高,且倾向于林业碳汇的价格由政府主导,而风险由交易双方共担。因此,激发林业碳汇需求须在掌握控排企业阶段性特征的基础上,通过碳交易制度创新,推进排放配额管理及林业碳汇融入国家碳排放权交易体系,同时稳定企业购买林业碳汇的收益预期。 相似文献
8.
从低碳经济测评指标体系研究现状出发,构建低碳系统测算环节图,根据能源消耗、治理环节,将低碳评价所涉及测算方法按碳排放、碳足迹、碳源控制、碳汇建设、碳中和五大类进行归纳和评述。各方法分别涉及产业结构、消费结构、能源结构以及能源利用率等碳排放影响因素。 相似文献
9.
设施蔬菜生产系统碳足迹研究——以北京市为例 总被引：4，自引：0，他引：4
设施蔬菜生产系统碳足迹研究对构建低碳蔬菜产业具有重要意义。基于生命周期法和多目标灰靶决策模型,利用2013年实地调查数据对北京市设施蔬菜生产系统碳足迹进行分析和评价。结果表明:1总碳排放中以间接碳排放为主,来自工业的投入品是产生碳排放的主要原因;2总体上看,设施蔬菜生产系统光合作用碳汇大于总碳排放,对生态环境具有正外部性;3大棚优于温室,但两者的总碳排放均小于光合作用碳汇,对生态环境均具有正外部性;4各地区碳足迹的优劣顺序为大兴区、通州区、顺义区、房山区、平谷区、延庆县、密云县和怀柔区,且前四个地区对生态环境具有正外部性。最后,根据研究结论提出了推进低碳设施蔬菜产业发展的几点建议。 相似文献
10.
基于2007-2013年中文社会科学引文索引(CSSCI)收录的图书馆嵌入式服务研究的110篇文献,利用知识图谱可视化软件Citespace Ⅲ对相关数据进行文献共引、名词短语、突现词等的处理与分析,揭示国内图书馆嵌入式服务研究的代表作者、核心机构及演进路径、研究前沿与热点,以期为我国图书馆嵌入式服务的研究提供有益参考。 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.
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
13.
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
14.
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
15.
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
16.
《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
17.
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
18.
《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
19.
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
20.
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