山东耕地生态保护存在的问题及对策     

王增如  许庆福  乔庆伟 《山东国土资源》2007,23(8):12-14,17

山东省作为一个粮食产销大省,国家的粮食主产区之一,搞好耕地保护十分重要。耕地生态保护是耕地保护的重要组成部分,是实现农业可持续发展的前提条件。从分析全省耕地数量及特点入手,阐述耕地生态环境存在的主要问题,针对存在的问题,提出耕地生态保护的对策。  相似文献   

我国耕地资源流失的原因及耕地保护对策研究     

成婧 《山东国土资源》2006,22(9):39-43

耕地资源是一种稀缺的公共资源,耕地保护是社会主义新农村建设的要务,是经济社会可持续发展的关键,是我国粮食安全的重要保障。在介绍我国耕地保护问题理论和现状的基础上,将耕地保护问题产生的原因归结为市场失灵,政府失败,法律制度的不完善及与经济发展、生态建设等的矛盾,并从制度层面提出了相应的对策建议。认为我国耕地保护应建立一个多元的管理体系,需要在耕地保护时引入公共管理的理念,利用“第三部门”来保护耕地。  相似文献   

日照市岚山区耕地需求与保护对策     

孟艳丽  白杨  丁喜莲 《山东国土资源》2007,23(9):21-23,27

日照市岚山区现有耕地虽能满足农产品需求,但不能保证建设用地需要。至2020年建设占用耕地需求量1 400hm2,耕地缺口较大;全区未利用土地质量差、开发难度大,耕地面临短缺的严峻形势。耕地保护的对策是控制人口增长,严格控制非农业建设占用耕地,积极进行土地整理复垦开发和改造中低产田,提高耕地生产力。  相似文献   

THE MIRE IN NORTHEAST OF CHINA     

张养贞  牛焕光 《中国地理科学(英文版)》1993,3(3):238-246

The northeast region is one of the principal mire distribution regions in China. According to the process of peat formation and accumulation , middle geomorphology type controlling water source supplement and the plant cover, 2 types, 10 subtypes and 27 mire bodies are divided. The mire area decreases gradually from north to south. There is more peat mire in the mountain and there is mainly gley mire without peat in the plain. The paper also explains the mire types in the principal mire distribution region and the utilization of mire in the fields of agriculture, forest, animal husbandry. The mire is a wetland ecosystem. It can reserve a lot of water, adjust rivers, humidify air. Thereby , attention must be paid to protecting ecological balance in the process of reclaiming mire and the mire protection.  相似文献   

Near‐infrared spectroscopy of a hydroecological indicator: new tool for determining sustainable yield for Floridan aquifer system     

Sydney T. Bacchus  Douglas D. Archibald  George A. Brook  Kerry O. Britton  Bruce L. Haines  Stephen L. Rathbun  Marguerite Madden 《水文研究》2003,17(9):1785-1809

Pond‐cypress (Taxodium ascendens Brong.) is a dominant canopy species in depressional wetlands of the south‐eastern Coastal Plain. Unsustainable withdrawals from the karst Floridan aquifer system have caused premature decline and death of pond‐cypress trees, presumably owing to altered hydroperiods (which alter the flow of water and nutrients in trees). There has been no scientifically based means to determine sustainable yield from this regional aquifer system or to detect early stages of physical/ecological damage associated with groundwater mining and aquifer storage and recovery (ASR, which also can alter natural hydroperiods). In this study, the relationship between visual symptoms (indicators) of stress or premature decline, and spectral reflectance was evaluated using dried, milled branch tips collected from natural stands of mature pond‐cypress. Depressional systems evaluated represented four of the six aquifer system subregions where subsurface perturbations from groundwater mining: (i) were presumed not to be occurring (reference wetlands); (ii) may be occurring but are not documented; and (iii) have been confirmed. Sampled trees were assigned to one of three stress classes (1, no/minimal; 2, moderate; 3, severe) based on the visual indicators. Partial least squares–linear discriminant analysis of second derivative spectral transformations in the visible/shortwave near‐infrared (NIR) region (400–1100 nm) and the NIR region (1100–2500 nm) was used to evaluate the samples in assigned classes. Class 1 samples were discriminated from combined class 2 and 3 samples in the NIR region with 100% and 97% accuracy for consecutive winter sample periods (before bud‐break). The percentage of correctly classified samples in this spectral region was lower (85%) for summer samples (full leaf‐out). Second‐derivative models for the NIR region developed from the winter data sets predicted assigned classes for alternate winter's samples with an accuracy of 97% and 100%. High correlation between spectral reflectance of dried, milled branch tips collected from mature pond‐cypress in winter and visual indicators of premature decline suggests in situ pond‐cypress are hydroecological indicators of anthropogenic subsurface hydroperiod perturbations. This approach provides objective means for early detection of unsustainable aquifer yield and adverse impacts from ASR activities in the south‐eastern Coastal Plain. Used in conjunction with hydrological monitoring and modelling, the hydroecological indicators should provide the means with which sustainable yield in the south‐eastern Coastal Plain can be achieved and maintained. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

NUMERICAL MODELLING FOR OFFSHORE PLATFORM CATHODIC PROTECTION-LOCAL SYSTEM   总被引：1，自引：0，他引：1  

曹圣山  王庆璋  张曼平 《中国海洋湖沼学报》1995,13(3):247-252

This paper discusses numerical methods for modelling cathodic protation (CP) using Boundary ElementMethods(BEM) for CP design analysis in comparision with the traditional methods and presentsseveral mathematical models (for CP design in 3-D infinite area) solvable by using BEM withmicrocomputer.  相似文献   

Resistance of salt marsh substrates to near-instantaneous hydrodynamic forcing     

Helen Brooks  Iris Möller  Simon Carr  Clementine Chirol  Elizabeth Christie  Ben Evans  Kate L. Spencer  Tom Spencer  Katherine Royse 《地球表面变化过程与地形》2021,46(1):67-88

Salt marshes deliver vital ecosystem services by providing habitats, storing pollutants and atmospheric carbon, and reducing flood and erosion risk in the coastal hinterland. Net losses in salt marsh areas, both modelled globally and measured regionally, are therefore of concern. Amongst other controls, the persistence of salt marshes in any one location depends on the ability of their substrates to resist hydrodynamic forcing at the marsh front, along creek margins and on the vegetated surface. Where relative sea level is rising, marsh elevation must keep pace with sea-level rise and landward expansion may be required to compensate for areal loss at exposed margins. This paper reviews current understanding of marsh substrate resistance to the near-instantaneous (seconds to hours) forcing induced by hydrodynamic processes. It outlines how variability in substrate properties may affect marsh substrate stability, explores current understanding of the interactions between substrate properties and erosion processes, and how the cumulative impact of these interactions may affect marsh stability over annual to decadal timescales. Whilst important advances have been made in understanding how specific soil properties affect near-instantaneous marsh substrate stability, less is known about how these properties interact and alter bulk substrate resistance to hydrodynamic forcing. Future research requires a more systematic approach to quantifying biological and sedimentological marsh substrate properties. These properties must then be linked to specific observable erosion processes, particularly at the marsh front and along creek banks. A better understanding of the intrinsic dynamics and processes acting on, and within, salt marsh substrates will facilitate improved prediction of marsh evolution under future hydrodynamic forcing scenarios. Notwithstanding the additional complications that arise from morphodynamic feedbacks, this would allow us to more accurately model the future potential protection from flooding and erosion afforded by marshes, while also increasing the effectiveness of salt marsh restoration and recreation schemes. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd  相似文献   

一种针对相交矿山巷道的三维建模方法     

唐敏  方源敏 《测绘科学》2011,36(4):240-241

利用传统的中线和断面结合的方法,对矿山巷道进行三维建模.一直以来传统的自动建模对巷道交汇处处理都有很大困难,本文主要研究处理巷道相交,特别是多条巷道相交情况下的平滑以及正确建模,提出各种实用的算法,给出解决方法并最终完成巷道建模.利用C语言完成编程实现,DirectX实现可视化,实验证明,建模方法可行,系统运行正常.  相似文献   

The existence of ‘complete similarities’ in the response of seismic isolated structures subjected to pulse‐like ground motions and their implications in analysis     

Nicos Makris  Michalis F. Vassiliou 《地震工程与结构动力学》2011,40(10):1103-1121

In this paper the seismic response of isolated structures supported on bearings with bilinear and trilinear behavior is revisited with dimensional analysis in an effort to better understand the relative significance of the various parameters that control the mechanical behavior of isolation systems. An isolation system that consists of lead rubber bearings or of single concave spherical sliding bearings exhibits bilinear behavior; whereas, when a double concave configuration is used the behavior is trilinear. For the case of bilinear behavior it is well known that the value of the normalized yield displacement is immaterial to the response of the isolated superstructure—or, in mathematical terms, that the response of the bilinear oscillator exhibits complete similarity in the dimensionless yield displacement. Similarly, for the case of trilinear behavior the paper shows that the presence of the intermediate slope is immaterial to the peak response of most isolated structures—a finding that shows the response of the trilinear oscillator exhibits a complete similarity in the difference between the coefficients of friction along the two sliding surfaces as well as in the ratio of the intermediate to the final slope. This finding implies that even when the coefficients of friction of the two sliding surfaces are different, the response of isolated structures for most practical configurations can be computed with confidence by replacing the double concave spherical bearings with single concave spherical bearings with an effective radius of curvature and an effective coefficient of friction. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

防雷装置设计审核和竣工验收行政许可档案管理的思考     

林常青  李嘉  林春 《气象与减灾研究》2011,34(3):68-71

防雷装置设计审核和竣工行政许可(简称防雷行政许可)是气象行政许可中的一个重要许可事项.防雷行政许可是各级气象行政主管机构根据公民、法人或者其他组织的申请,经依法审查,准予其从事防雷设计施工等相关活动的行政性管理行为.随着行政审批事项数量的逐年增大,要求防雷行政许可档案管理规范化、严格化.通过总结防雷行政许可工作实践经验...  相似文献