Application of vertically integrated sampling approach to study of new production via ²³⁴Th-²³⁸U disequilibria     

Chen Feizhou  Huang Yipu  Chen Min 《海洋学报(英文版)》2000,19(2):37-44

I~IOWBecause of the imPOrtance of new production in the studies of the structure and function ofmarine eCOSystem and carhan cycleS, one should pay great attention tO the study of new production in biological oceanography, biogeOChendstry, and especially in the study of global change(Plait et al., 1992; Jiao and Wang, 1993; Wang, 1992). With the deepening of the study ofnew production, it has been found that the spatial and temporal distributions of new preductionvary largely in different…  相似文献   

Living (Stained) Benthic Foraminifera and their Response to the Seasonal Hydrographic Cycle, Periodic Hypoxia and to Primary Production in Havstens Fjord on the Swedish West Coast     

M. Gustafsson  K. Nordberg 《Estuarine, Coastal and Shelf Science》2000,51(6):743

Havstens Fjord on the Swedish west coast is a silled fjord that is characterized by strong stratification and stagnant bottom-water with periodically occurring hypoxic (0–2 ml l⁻¹) or anoxic (≤0 ml l⁻¹) conditions. Renewal of Havstens Fjord's deep-water occurs every year, mostly during winter or spring. The aim of this study was to discover how living benthic Foraminifera respond to hydrographic variations, periodic oxygen deficiency and variations in primary production. A long series of monthly hydrographic measurements combined with sediment sampling were performed from August 1993 to December 1994. Sampling was carried out at four different sites along a depth transect (12, 20, 30 and 40 m). Monthly values of chlorophyll a from the water surface down to 15 m were obtained. With increasing water depth, the foraminiferal fauna changed from a low diverse brackish fauna, through a diverse and abundant fauna, to a low diversity and sparse fauna characterized by species tolerant of oxygen depletion. At the deepest site (40 m) Elphidium magellanicum and Stainforthia fusiformis survived five months of anoxic or near anoxic conditions. At 30 m the periodic hypoxic conditions were severe enough to prevent a rich benthic macrofauna establishing, but there was enough oxygen for an abundant and diverse foraminiferal fauna to thrive. Under oxic conditions, freshly sedimented phytoplankton seem to be an important food source for the Foraminifera.  相似文献   

东海与泥底辟构造有关的天然气水合物初探   总被引：6，自引：2，他引：4  

赵汗青  吴时国  徐宁  王秀娟  张光学 《现代地质》2006,20(1):115-122

根据所获得的高分辨率地震资料分析,发现冲绳海槽南部西侧槽坡附近以及海槽内部发育有一系列泥火山（底辟）构造,在地形上表现为泥火山地貌,在穿过泥火山的地震剖面上,表现出典型的泥底辟构造。对穿过泥底辟构造的DMS01-5地震剖面进一步的处理和解释发现,泥底辟构造顶部存在明显的似海底反射（BSR）,其与海底反射波组极性相反,在BSR之上存在振幅空白带,在速度谱上出现速度异常,指示存在与泥火山有关的天然气水合物。从世界广泛发现的与泥底辟构造有关的天然气水合物来看,天然气水合物既可以在泥底辟构造的丘状外围成藏,也可以在其外围的海底沉积物中产出。在泥底辟构造的丘状外围附近,天然气水合物的形成机制类似于传统的矿物低温热液的形成;在泥底辟构造外围海底沉积物中,其形成过程类似于传统的矿物交代形成机制。冲绳海槽泥底辟构造的发育与很高的沉积速率和槽坡的活动断层有关。在冰期期间,长江携带大量的陆源物质直接输送到大陆坡地区,沉积速率达300 m/Ma,产生异常高压,同时张性断层极为发育,为流体的迁移提供了良好的通道,在异常压力以及上覆地层压力作用下大量流体向上运移,从而发育大量的泥底辟构造。富含甲烷的流体易在其外围及外围海底沉积物中形成天然气水合物藏。  相似文献   

多油层分层参数测试新方法研究与实践     

赵忠健  何志祥  李治平 《地质力学学报》2006,12(1):71-76

针对传统的压力恢复/压力降落试井方法存在的测试时间长、影响油井产量、难以获得分层地层参数等缺陷,将生产测井的流量流压资料应用到试井领域,提出了变流量法、流量-压力波动曲线法两种多油层试井新方法,实现了在油井正常生产的情况下,求取井下各小层的地层压力、渗透率、污染系数等分层地层参数,较好地解决了多层合采油井的分层参数测试难题。详细地阐述了两种多油层试井新方法的测试原理,并列举了其现场应用情况。   相似文献   

21世纪初中国主要余粮区的空间格局特征   总被引：16，自引：0，他引：16  

殷培红  方修琦  田青  马玉玲 《地理学报》2006,61(2):190-198

利用2000~2003年分县统计数据,以人均占有量为指标,重点研究21世纪初中国粮食主产区的空间格局及区域差异。研究结果表明：20世纪90年代后期以来,中国粮食生产重心进一步北移,同时出现“西扩”趋势。目前,20世纪90年代后期国家确立的粮食生产大县中近1/3人均粮食占有量已不足400kg,多分布在南方。全国3/4左右的余粮集中出产在东北地区、华北平原中南部地区、西部干旱、半干旱地区;2/3的余粮地区位于环境变化敏感地区,粮食产量波动大。这些地区的粮食丰歉直接影响到全国粮食市场价格的波动,中国粮食安全自然风险增大。加强上述地区的环境变化及粮食安全的自然风险研究,提高适应环境变化能力势在必行。  相似文献   

中国不同气候带各类型森林的生物量和净第一性生产力   总被引：27，自引：0，他引：27  

李高飞  任海 《热带地理》2004,24(4):306-310

根据<中国植被>的区划,将收集的全国984个样点的森林数据归并到5种气候带类型中,计算了各类型森林以及同一类型森林(分人工林和天然林)的生物量和净第一性生产力,还计算了不同气候带森林各器官的平均生物量和净第一性生产力.结果表明,从寒温带到热带各类型森林的生物量和净第一性生产力逐渐增加,天然林的生物量大于人工林生物量;除热带林外,人工林的净第一性生产力大于天然林净第一性生产力.  相似文献   

区域土地利用变化及其对粮食生产影响分析——以山东省为例   总被引：13，自引：2，他引：11  

邵晓梅 《地理科学进展》2003,22(1):30-37

土地利用变化及其效应是目前全球变化研究的热点之一。本文以山东省为例,在分析土地利用结构特点和粮食总产量的时间变化趋势的基础上,进一步探讨了土地利用变化对粮食生产的影响。其影响主要表现在:土地利用类型变化与粮食播种面积、土地利用程度变化与粮食总产、土地利用集约度与粮食单产等三个方面。针对上述影响进一步探讨了保障粮食生产可持续发展的措施及土地利用分区,可为区域土地利用取向和制定粮食发展政策提供科学依据。  相似文献   

用土工合成材料治理道路翻浆的研究   总被引：4，自引：1，他引：3  

霍凯成  张全林  罗国荣 《岩土力学》2003,24(1):45-48

介绍了各种土工合成材料的排水、隔离、渗滤、加筋等功能作用。根据路基土的物理力学性能和水力性能与土工合成材料的材料特性,决定采用复合土工膜、沥青玻璃布、沥青棉胶布、竹排等,工程实践表明,采用了土工合成材料后,大大减轻了路基冻害现象,不失为一种较为理想的治理路基翻浆冒泥的方法。土工合成材料治理道路翻浆,可以使路基的破损程度降到最低,为车辆运行提供平坦的路面。  相似文献   

Impacts of Land Fragmentation and Cropping System on the Productivity and Efficiency of Grain Producers in the North China Plain: Taking Cangxian County of Hebei Province as an Example     

WANG Xue  LI Xiubin 《资源与生态学报(英文版)》2020,11(6):580-588

Land fragmentation is widely known to have an impact on farm performance. However, previous studies investigating this impact mainly focused on a single crop, and only limited data from China are available. This study considers multiple crops to identify the impact of land fragmentation (LF), as well as cropping system (CS), on farm productivity and the efficiency of grain producers in the North China Plain (NCP), using Cangxian County of Hebei Province as an example. Detailed household- and plot-level survey data are applied and four stochastic frontier and inefficiency models are developed. These models include different sets of key variables in either the production function or the inefficiency models, in order to investigate all possibilities of their influences on farm productivity and efficiency. The results show that LF plays a significant and detrimental role, affecting both productivity and efficiency. A positive effect is evident with respect to the CS variable, i.e., multiple cropping index (MCI), and the wheat-maize double CS, rather than the maize single CS, is usually associated with higher farm productivity and efficiency. In addition to LF and CS, four basic production input variables (labor, seed, pesticide and irrigation), also significantly affect farmers’ productivity, while the age of the household head and the ratio of the off-farm labor to total labor are significantly relevant to technical inefficiency. Policies geared toward the promotion of land transfer and the rational adjustment of cropping systems are recommended for boosting farm productivity and efficiency, and thus maintaining the food supply while mitigating the overexploitation of groundwater in the NCP.  相似文献   

重庆市江津区乡村生产空间系统适应性评价及障碍因素分析   总被引：1，自引：0，他引：1  

王成  龙卓奇  樊荣荣 《地理研究》2020,39(7):1609-1624

研究在解析乡村生产空间系统适应性内涵、构建其分析框架的基础上,从易损性、稳定性、响应三个维度构建乡村生产空间系统适应性评价指标体系,运用适应性评价模型评价重庆市江津区近11年乡村生产空间系统运行状态,辅以障碍度模型诊断并测算其适应性障碍因子和适应性障碍度,进而提出针对性策略以破解其所面临的现实困境,结果表明：2007—2017年江津区乡村生产空间系统适应性总体呈波动上升且不断增强趋势,系统可持续发展能力稳步提高;系统适应性障碍度由稳定性、响应障碍向易损性障碍转变,其关键障碍因子为化肥使用量、农膜使用量、乡村生产总耗能、城镇工矿用地面积、乡村环保投资额占比等;以发展生态农业、有机农业,强化环境保护为前提降低系统易损性,拓展富硒特色农业增值空间和有效增加乡村资金、人才与技术投入提升稳定性与响应能力是增强乡村生产空间系统适应能力的关键。  相似文献