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981.
Seasonal and interannual variations of carbon exchange over a rice-wheat rotation system on the North China Plain 总被引:2,自引:0,他引:2
Chen Chen Dan Li Zhiqiu Gao Jianwu Tang Xiaofeng Guo Linlin Wang Bingcheng Wan 《大气科学进展》2015,32(10):1365-1380
Rice-wheat (R-W) rotation systems are ubiquitous in South and East Asia, and play an important role in modulating the carbon cycle and climate. Long-term, continuous flux measurements help in better understanding the seasonal and interannual variation of the carbon budget over R-W rotation systems. In this study, measurements of CO2 fluxes and meteorological variables over an R-W rotation system on the North China Plain from 2007 to 2010 were analyzed. To analyze the abiotic factors regulating Net Ecosystem Exchange (NEE), NEE was partitioned into gross primary production (GPP) and ecosystem respiration. Nighttime NEE or ecosystem respiration was controlled primarily by soil temperature, while daytime NEE was mainly determined by photosythetically active radiation (PAR). The responses of nighttime NEE to soil temperature and daytime NEE to light were closely associated with crop development and photosynthetic activity, respectively. Moreover, the interannual variation in GPP and NEE mainly depended on precipitation and PAR. Overall, NEE was negative on the annual scale and the rotation system behaved as a carbon sink of 982 g C m-2 per year over the three years. The winter wheat field took up more CO2 than the rice paddy during the longer growing season, while the daily NEE for wheat and rice were -2.35 and -3.96 g C m-2, respectively. After the grain harvest was subtracted from the NEE, the winter wheat field became a moderately strong carbon sink of 251-334 g C m-2 per season, whereas the rice paddy switched to a weak carbon sink of 107-132 per season. 相似文献
982.
芬兰北部的金矿床数量众多,大多数金矿床(点)产出于古元古界中央拉普兰绿岩带(CLGB)和库萨莫—帕拉波加片岩带内,主要分为3种类型:造山型金矿、铁氧化物铜-金(IOCG型)矿床及砂金矿。其中造山型金矿绝大部分分布于中央拉普兰绿岩带中部及库萨默地区和帕拉波加地区,最常见的矿石矿物为黄铁矿、毒砂、黄铜矿和磁黄铁矿,其次为方铅矿、闪锌矿、黝铜矿等。围岩蚀变包括钠长石化、绢云母化、黑云母化、碳酸盐化及绿泥石化。造山型金矿床主要控制因素包括构造、岩性和造山期区域变质。IOCG型矿床主要分布在CLGB的西部克拉瑞地区,容矿围岩是钠长石-直闪石石棉型岩石,矿石中富含Fe-Cu-Au±Ag、Bi、Ba、Co、Mo、Sb、Se、Te、Th、U和轻稀土元素。围岩蚀变强烈,并且有明显的分带现象。IOCG型金矿床的形成受岩浆热液活动和构造的影响较大。砂金矿床包括古砂金矿床和现代砂金矿床,主要分布在CLGB东北部。芬兰北部金矿床的研究对北极圈及邻区的找矿勘查工作具有重要意义,也为中国胶东半岛、华北克拉通北缘、小秦岭和秦岭地区及新疆北部地区进一步金矿勘查提供参考。 相似文献
983.
渤海高地饱压差油藏有着高地饱压差、储层压力变化幅度大等特点,为明确此类油藏应力敏感特性对于其储层产能的影响,论文以Q油田W组油藏为例,在岩心覆压气测渗透率实验的基础上,通过改变岩心有效应力,得出了岩心渗透率与所受有效应力的变化规律。实验表明岩心渗透率与其所受有效应力存在着乘幂式关系,将此变化规律应用于产能分析中,推导考虑应力敏感的稳态产能公式,并绘制产能图版进行对比分析。考虑应力敏感后的产能明显出现整体降低的现象,在不同的储层渗透率下,都存在一个相应的最优生产压差限,这对于渤海高地饱压差油藏合理生产制度的制定具有指导意义。 相似文献
984.
运用模型分析法和比较研究法研究中国1982—2012年不同经济发展水平下粮食生产要素的生产弹性和贡献率的差异。我国粮食生产要素的生产弹性和贡献率在发达地区和中等发达地区存在显著性差异。首先,土地和化肥对两类地区的粮食生产都有显著的正向影响,其中,在发达地区,土地和化肥的生产弹性和贡献率显著高于中等发达地区;其次,劳动力、农业机械、有效灌溉面积和农村用电量对两个地区粮食产量的影响差异也很大。我国粮食生产要素的贡献与经济发展水平密切相关,生产要素价格对贡献率有重要影响。实现我国粮食增产的关键在于生产要素的优化配置。 相似文献
985.
Land consolidation: An indispensable way of spatial restructuring in rural China1简 总被引:36,自引:10,他引:26
LONG Hualou 《地理学报(英文版)》2014,24(2):211-225
The implementation of new type industrialization and urbanization and agricultural modernization strategies lacks of a major hand grip and spatial supporting platform, due to long-term existed "dual-track" structure of rural-urban development in China as well as un- stable rural development institution and mechanism. It is necessary to restructure rural pro- duction, living and ecological space by carrying out land consolidation, so as to establish a new platform for building new countryside and realizing urban-rural integration development in China. This paper develops the concept and connotation of rural spatial restructuring. Basing on the effects analysis of industrialization and urbanization on rural production, living and ecological space, the mechanism of pushing forward rural spatial restructuring by carry- ing out land consolidation is probed. A conceptualization of the models of rural production, living and ecological spatial restructuring is analyzed combining with agricultural land con- solidation, hollowed villages consolidation and industrial and mining land consolidation. Fi- nally, the author argues that a "bottom-up" restructuring strategy accompanied by a few "top-down" elements is helpful for smoothly pushing forward rural spatial restructuring in China. In addition, the optimization and restructuring of rural production, living and ecological space will rely on the innovations of regional engineering technology, policy and mechanism, and mode of rural land consolidation, and more attentions should be paid to rural space, the foundation base and platform for realizing urban-rural integration development. 相似文献
986.
龙花楼 《地理学报(英文版)》2014,(2)
The implementation of new type industrialization and urbanization and agricultural modernization strategies lacks of a major hand grip and spatial supporting platform, due to long-term existed "dual-track" structure of rural-urban development in China as well as unstable rural development institution and mechanism. It is necessary to restructure rural production, living and ecological space by carrying out land consolidation, so as to establish a new platform for building new countryside and realizing urban-rural integration development in China. This paper develops the concept and connotation of rural spatial restructuring. Basing on the effects analysis of industrialization and urbanization on rural production, living and ecological space, the mechanism of pushing forward rural spatial restructuring by carrying out land consolidation is probed. A conceptualization of the models of rural production, living and ecological spatial restructuring is analyzed combining with agricultural land consolidation, hollowed villages consolidation and industrial and mining land consolidation. Finally, the author argues that a "bottom-up" restructuring strategy accompanied by a few "top-down" elements is helpful for smoothly pushing forward rural spatial restructuring in China. In addition, the optimization and restructuring of rural production, living and ecological space will rely on the innovations of regional engineering technology, policy and mechanism, and mode of rural land consolidation, and more attentions should be paid to rural space, the foundation base and platform for realizing urban-rural integration development. 相似文献
987.
World cities and international organizations: Political global-city status of Chinese cities 总被引:3,自引:1,他引:2
In this study, the authors use a political perspective to explore the relative global status of cities in China. Two questions are addressed. Firstly, by using international organizations as the subjects and quantitative analysis of the spatial distribution of their offices, the overall position of Chinese cities in the global distribution of international organizations is estimated. The results show that 22 Chi- nese cities are involved in international political affairs. Beijing, Shanghai and Guangzhou dominate these activities and have high po- litical global-city status. Secondly, through qualitative analysis of Guangzhou City, the authors explore how its status as a center for intemational organizations has been shaped in recent years. The locational decision-making process is analyzed and the factors are demonstrated at both national and city scales. The definition of international organizations as used in this study refers not only to those supranational bodies that have the ability to manage relations across states (such as the European Union), but also those in- ter-governmental organizations (IGOs), international non-governmental organizations (INGOs) and diplomatic representatives and delegations that today also manage and regulate relations between and among states. 相似文献
988.
Surplus production models are the simplest analytical methods effective for fish stock assessment and fisheries management. In this paper, eight surplus production estimators (three estimation procedures) were tested on Schaefer and Fox type simulated data in three simulated fisheries (declining, well-managed, and restoring fisheries) at two white noise levels. Monte Carlo simulation was conducted to verify the utility of moving averaging (MA), which was an important technique for reducing the effect of noise in data in these models. The relative estimation error (REE) of maximum sustainable yield (MSY) was used as an indicator for the analysis, and one-way ANOVA was applied to test the significance of the REE calculated at four levels of MA. Simulation results suggested that increasing the value of MA could significantly improve the performance of the surplus production model (low REE) in all cases when the white noise level was low (coefficient of variation (CV)=0.02). However, when the white noise level increased (CV=0.25), adding the value of MA could still significantly enhance the performance of most models. Our results indicated that the best model performance occurred frequently when MA was equal to 3; however, some exceptions were observed when MA was higher. 相似文献
989.
外向型汉语学习词典是为母语非汉语的学习者编纂的学习汉语用的词典。20世纪80年代以来,词典编纂成果数量较多,品种较全,类型意识在逐渐增强,培育出了几部品牌产品;但在类型定位、用户意识、编纂技术、品牌观念等方面仍需加强。在研究方面,出现了一批较有分量的论文和专著,研究内容不断深入,研究队伍不断壮大;但与国外发达水平相比,仍有较大差距,主要表现在理论研究滞后于编纂实践、学科仍不成熟、学术流派尚未形成等。 相似文献
990.
LONG Hualou 《地理学报》2014,24(2):211-225
The implementation of new type industrialization and urbanization and agricultural modernization strategies lacks of a major hand grip and spatial supporting platform,due to long-term existed "dual-track" structure of rural-urban development in China as well as unstable rural development institution and mechanism. It is necessary to restructure rural production,living and ecological space by carrying out land consolidation,so as to establish a new platform for building new countryside and realizing urban-rural integration development in China. This paper develops the concept and connotation of rural spatial restructuring. Basing on the effects analysis of industrialization and urbanization on rural production,living and ecological space,the mechanism of pushing forward rural spatial restructuring by carrying out land consolidation is probed. A conceptualization of the models of rural production,living and ecological spatial restructuring is analyzed combining with agricultural land consolidation,hollowed villages consolidation and industrial and mining land consolidation. Finally,the author argues that a "bottom-up" restructuring strategy accompanied by a few "top-down" elements is helpful for smoothly pushing forward rural spatial restructuring in China. In addition,the optimization and restructuring of rural production,living and ecological space will rely on the innovations of regional engineering technology,policy and mechanism,and mode of rural land consolidation,and more attentions should be paid to rural space,the foundation base and platform for realizing urban-rural integration development. 相似文献