共查询到20条相似文献，搜索用时 46 毫秒
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根据 2 0 0 1年 11至 2 0 0 2年 1月间北部湾海域秋、冬季 2个航次的底拖网渔业资源调查资料 ,对北部湾海域甲壳类的种类组成及分布进行研究。本次调查共渔获虾类 2 4种 ,隶属于 6科 11属 ;蟹类 30种 ,隶属 9科 19属 ;虾蛄 9种 ,隶属 2科 6属。各种类沿水深和地理分布有明显变化 ,主要集中分布于湾中部水深 2 1～ 80m海域。 相似文献
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Mollisols properties and changes in Ukraine and China 总被引：4，自引：2，他引：2
Soils are the foundation of civilizations and the basis for human food production.Mollisols in Ukraine and Northeast China are two out of the four major Mollisol regions in the world.The natural areas from which Mollisols developed are the prairies and steppes that experience temperate and freezing conditions.This review paper introduces the general climate,vegetation,and topography of Mollisols regions in Ukraine and Northeast China,analyzes their properties,including soil texture,soil organic matter content,soil bulk density,pH,cation exchange capacity and other chemical properties,and compares the property changes and management practices of Mollisols in relation to sustainable grain production. 相似文献
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Pak-TaoLeung CarlH.Gibson 《中国海洋湖沼学报》2004,22(1):1-23
Turbulence is defined as an eddy-like state of fluid motion where the inertial-vortex forces of the eddies are larger than any of the other forces that tend to damp the eddies out. Energy cascades of irrotational flows from large scales to small are non-turbulent, even if they supply energy to turbulence. Turbulent flows are rotational and cascade from small scales to large, with feedback. Viscous forces limit the smallest turbulent eddy size to the Kolmogorov scale. In stratified fluids, buoyancy forces limit large vertical overturns to the Ozmidov scale and convert the largest turbulent eddies into a unique class of saturated, non-propagating, internal waves, termed fossil-vorticity-turbulence. These waves have the same energy but different properties and spectral forms than the original turbulence patch. The Gibson (1980, 1986) theory of fossil turbulence applies universal similarity theories of turbulence and turbulent mixing to the vertical evolution of an isolated patch of turbulence in a stratified fluid as its growth is constrained and fossilized by buoyancy forces. Quantitative hydrodynamic-phase-diagrams (HPDs) from the theory are used to classify microstructure patches according to their hydrodynamic states. When analyzed in HPD space, previously published oceanic datasets showed their dominant microstructure patches are fossilized at large scales in all layers. Laboratory and field measurements suggested phytoplankton species with different swimming abilities adjust their growth strategies by pattern recognition of tur-bulence-fossil-turbulence dissipation and persistence times that predict survival-relevant surface layer sea changes. New data collected near a Honolulu waste-water outfall showed the small-to-large evolution of oceanic turbulence microstructure from active to fossil states, and revealed the ability of fossil-density-turbulence patches to absorb, and vertically radiate, internal wave energy, information, and enhanced turbulent-mixing-rates toward the sea surface so that the submerged waste-field could be detected from a space satellite (Bondur and Filatov, 2003). 相似文献
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JIN Huijun SUN Guangyou YU Shaopeng JIN Rui HE Ruixia 《中国地理科学(英文版)》2008,18(1):62-69
Recently, the degradation of permafrost and marsh environments in the Da and Xiao Hinggan Mountains has become a great concern as more human activities and pronounced climate warming were observed during the past 30 years and projected for the near future. The distr/bution patterns and development mechanisms of the permafrost and marshes have been examined both in theories and in field observations, in order to better understand the symbiosis of permafrost and marshes. The permafrost and marshes in the Da and Xiao Hinggan Mountains display discernible zonations in latitude and elevation. The marsh vegetation canopy, litter and peat soil have good thermal insulation properties for the underlying permafrost, resulting in a thermal offset of 3 ℃ to 4℃ and subsequently suppressing soil temperature. In addition, the much higher thermal conductivity of frozen and ice-rich peat in the active layer is conducive to the development or in favor of the protection of permafrost due to the semi-conductor properties of the soils overlying the permafrost. On the other hand, because permafrost is almost impervious, the osmosis of water in marsh soils can be effectively reduced, timely providing water supplies for helophytes growth or germination in spring. In the Da and Xiao Hinggan Mountains, the permafrost degradation has been accelerating due to the marked climate warming, ever increasing human activities, and the resultant eco-environmental changes. Since the permafrost and marsh environments are symbiotic and interdependent, they need to be managed or protected in a well-coordinated and integrated way. 相似文献
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小城市和建制镇土地集约利用程度低 发达国家的城镇化历程表明,城镇化水平达到30％后,城镇化即驶入快车道。目前,我国城镇化水平接近40％,已进入加速发展阶段,这一过程不依人们的意志为转移,也是我国实现现代化的必经之路。同时,我国城镇化水平还 相似文献
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城镇地籍调查是国土资源管理的一项重要的基础性工作,是城镇土地登记的法定程序,主要内容包括土地权属调查和地籍测量。该文分析探讨了土地权属调查政策、调查程序以及地籍测量技术的创新及应用,对城镇地籍初始和变更地籍调查具有一定的指导和借鉴作用。 相似文献
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Systematic studies of the changes in dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorus (DIP) and their
effects on phytoplankton over the last 30 years in the Bohai Sea are presented. The amount of sewage disposal, use of fertilizer
and the Huanghe River runoff were found to have a significant influence on the DIN or DIP concentrations in the Bohai Sea
over the last 30 years. Moreover, the changes in DIN and DIP resulted in changes in the limiting nutrients of phytoplankton
in the Bohai Sea from nitrogen in the early 1980s to nitrogen-phosphorus in the late 1980s, and then to phosphorus after the
1990s. In addition, changes in nitrogen and phosphorus had a significant effect on the phytoplankton community structure.
The half saturation constant (K
s) was used to evaluate the effect of nutrients on the phytoplankton community structure in the Bohai Sea over the last 30
years. Cell abundance percentages of dominant phytoplankton species with high K
s values for phosphorus and low K
s values for nitrogen have decreased since the 1980s, while those of dominant phytoplankton species with low K
s values for phosphorus and high K
s values for nitrogen increased during this period. 相似文献
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以章丘地区土壤为对象,系统分析了表层、深层土壤及8条剖面土壤中Se元素的含量水平,研究了土壤中Se的分布特征及其与土壤类型、成土母质、地形地貌和土壤理化性质及组分的关系。结果表明：章丘地区表层土壤中Se含量在0.1～0.8mg/kg之间,以中硒土壤为主,富硒土壤面积173km2。土壤类型中,水稻土Se平均含量水平最高,为0.55mg/kg;成土母质中以石炭—二叠纪泥页岩发育的土壤Se含量最高;剖面土壤中的Se主要在表层富集。影响章丘地区土壤Se含量分布的主要因素是成土母质、地形地貌、土壤pH、有机质及土壤中硫、铁铝氧化物等组分。 相似文献
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王有春 《广东海洋大学学报》2002,22(5):49-52
我国的民主党派既不同于执政党 ,也不同于反对党 ,它们是接受中国共产党领导、致力于社会主义现代化建设的参政党。所谓参政 ,首先是参加国家政权 ,其次是参与国家大政方和国家领导人人选的协商 ,其三是参与国家事务的管理。民主党派不仅要参政 ,还要对执政的中国共产党进行有效的监督 ,因为执政党 .的状况如何 ,路线、方、政策正确与否 ,直接关系到社会主义事业的兴衰成败。所以 ,作为执政党的中国共产党 ,一定要充分认识并切实发挥各民主党派的监督作用。 相似文献
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Selected trace metals(Pb, Cd, Cu, Hg) and arsenic in seawater and surface sediments of Laizhou Bay were determined, to evaluate their spatial distribution, pollution risk and potential ecological risk. Concentrations of the elements were 0.56–2.07, 0.14–0.38, 12.70–18.40, 0.014–0.094, and 1.13–2.37 μg/L in the seawater and 8.94–32.2, 0.18–0.67, 4.51–30.5, 0.006–0.058, and 5.75–15.3 mg/kg in sediments for Pb, Cd, Cu, Hg and As, respectively. High concentrations of the trace metals and arsenic in seawater and surface sediments were generally observed near the river estuary. The pollution risk result of the elements showed that Cu was the prominent trace metal pollutant in seawater, followed by Hg, Pb, Cd and As. The metal complex pollution index in seawater was at a medium level. The most important trace metal pollutant in sediments was Cd, followed by As, Cu, Pb, and Hg. Our pollution assessment suggests that trace metal pollution in Laizhou Bay sediments was at a low level. The potential ecological risk was also low in surface sediment. 相似文献
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Evaluation and analysis of provincial differences in resources and environment carrying capacity in China 总被引：2，自引：0，他引：2
Resources and environment carrying capacity is central to not only regional sustainable development but also major function-oriented zoning. This paper presents an evaluation index system for resources and environment carrying capacity based on four aspects of carrying capacity(i.e., water resources, land resources, the environment, and ecosystems) by using a square deviation decision-making method, and on the basis of above effort evaluates the resources and environment carrying capacity across 31 provincial regions in China(not including Hong Kong, Macau and Taiwan regions of China). In addition, this paper evaluates the current state of socio-economic development, and analyzes the spatial distribution of resources and environment pressure. The results showed that distinct spatial differences in resources and environment carrying capacity and pressure across provincial regions. Resources and environment pressure is affected by both comprehensive resources and environment carrying capacity and socio-economic development. Regions subjected to lower degrees of resources and environment pressure will be restricted by resources and environmental problems through future courses of development owing to excessively low carrying capacities. By contrast, regions with higher comprehensive resources and environment carrying capacity will be subjected to excessively high levels of resources and environment pressure because of rapid socio-economic development. Both of resources and environment carrying capacity and pressure must therefore be considered in the allocation of country-binding targets to provincial regions. 相似文献
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Distribution of Aluminum and Fluoride in Tea Plant and Soil of Tea Garden in Central and Southwest China 总被引：4，自引：0，他引：4
The distribution of Al and F contents and the relationship between Al and F in tea plants and soils of 12 tea gardens in Central and Southwest China were investigated from October 31 to November 14, 2006. The results show that there were differences in pH, CEC, the contents of organic matter (OM), Al and F in the different soils of the tea gardens. The Al content ranged from 1196 to 7976mg/kg for old leaf, 370 to 2681mg/kg for young leaf and 285 to 525mg/kg for stem, whereas the content of F ranged from 221 to 1504mg/kg for old leaf, 49 to 602mg/kg for young leaf and 13.5 to 77.5mg/kg for stem. The concentrations of labile Al varied obviously in the different soils, but the distribution law of labile Al content for the same garden was Alexchangeable≈AlFe-Mn oxide>Alorganic>Alwater-soluble. The contents of different labile F fractions varied slightly in the different soils and the different soil layers, though the exchangeable F content was lowest among the labile F in the soils. The concentrations of Al and F in tea plants increased with increasing amount of water-soluble Al or F, especially the amount of water-soluble fractions in the soil layer of 0-20cm.The correlation between Al content and F content in the tea leaf was more significant than that in the tea stem. Furthermore, the correlation between Al content and F content in whole tea plant was strongly significant (r=0.8763, p<0.01, n=36). There were evident tendency that Al concentration increased with the increase of F concentration in different soil layers. The correlation of water-soluble Al with water-soluble F in all soils was also strongly significant (r=0.7029, p<0.01, n=34). The results may provide a proof that Al and F are jointly taken up by tea plants to some extent in natural tea gardens. 相似文献
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《中国地理科学(英文版)》2019,(3)
Physical geography is the cornerstone of geography. In this article, the starting points of disciplines in physical geography in recent years in China are discussed. With the coupling of systems set as the research object, and sustainable development as the ultimate goal, the upgrade of physical geography can be deconstructed into three steps: deepen physical geography from the perspective of pattern-process coupling, improve the focus of physical geography from ecosystem processes to ecosystem services, and increase the understanding of the physical geography ‘pattern, process, service, sustainability' research cascade. The incorporation of human activities into physical geographic processes is essential to conduct integrated analysis on physical and human factors at different scales. The development of ecosystem service models that couple supply-demand and sustainable development are of great importance to bridge the role of ecosystem services between the natural environment and human well-being. Moreover, human-land systems and sustainable development have become the core areas and frontiers of integrated physical geography and even geography in general. China faces the great strategic demand of constructing an ecological civilization in a new era, and the development of the disciplines of physical geography should give full access to the advantages of intersecting and comprehensive disciplines, focus on the human-land system patterns,processes, and services in key research areas, and provide disciplinary support for regional, national, and global sustainable development. 相似文献
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本文利用全国1∶100万土地利用数据和1∶400万土壤肥力综合质量数据,从耕地的地形特征和土壤肥力两个角度,对贫困地区和非贫困地区的耕地自然质量进行比较研究。研究表明:贫困地区平原型、丘陵型耕地比重较低、山地型和陡坡型耕地比重较高;贫困地区耕地土壤肥力的平均水平和非贫困地区差别不大,但土壤肥力好和较好的耕地所占比重较小。本文还建立了包括地形特征和土壤肥力综合质量两个因素的耕地自然质量评价指数,从县域尺度对全国耕地自然质量进行定量评价,并发现贫困地区耕地自然质量评价指数在低值区集中的特征更为显著。 相似文献
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Investigations of natural and artificial radioisotopes including 90Sr,137Cs, gross B and U carried out in the Yellow Sea and adjacent southeast area in 1963. 1964, 1975 and 1978 showed that radioactive pollution by 90Sr and 137Cs from atmospheric fallout had gradually decreased with time due to the cessation of atmospheric nuclear weapons tests in the 70s. The distributions of natural and artificial radioactive isotopes (U, Ra, Th. 40K and 137Cs) in sediments southwest of Jizhou Island were uniform. The more uniform may be related to the soluble species of U[Uo2(CO3)4] in the seawater.The high value of Th at stations 3 and 6 was related to the sandy clay sediment; the low value at station 8 was related to sandy sediment. The content of 137Cs in the eddy area being less than about half of that in the China inshore area showed that the source of Cs may be insufficient orthat the conditions for enriching " Cs in the circulation eddy area were not favorable. 相似文献
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我国是一个人口大国,但土地资源有限。近年来,随着经济的迅猛发展,非农建设用地量的激增与有限的土地资源矛盾加剧。合理利用每一寸土地和切实保护好耕地,是我国长期坚持的一项战略目标和基本国策。为全面提高土地的利用率,提升土地综合生产能力,国家不断加强土地管理,把土地开发整理工作摆到了重要位置。东营市充分运用国家加强保护耕地的政策,紧紧围绕“三农”发展这一中心,充分发挥土地后备资源优势,积极争取、实施土地开发整理项目。提高了耕地质量,改善了农村生产、生活条件,有力地支持了社会主义新农村建设,促进了全市农业和农村经济持续快速健康发展。1土地开发整理项目基本情况东营市位于山东省北部黄河入海口处,辖区地理坐标为北纬36°55′~38°10′,东经118°07′~119°10′。辖3县2区,人口180万。东、北两面滨临渤海,总面积7 923 km2。东营市共有土地后备资源35万hm2,开发整理潜力大,通过开发整理复垦,全市可新增耕地87 826.55 hm2。多年来,在上级有关部门和东营市委、市政府的领导支持下,东营市土地开发整理工作取得了辉煌的业绩。自1999年新土地管理法实施以来,国家、省、市先后在东营市正式批复实施土地... 相似文献
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