高坝对乌江下游底栖动物群落结构的影响     

池仕运  陈胜  李嗣新  汪红军  周连凤  赵先富  郑金秀  胡俊  胡菊香 《湖泊科学》2019,31(2):469-481

基于2006-2016年近10年的长期监测数据,对乌江下游两座高坝的修建对底栖动物群落结构的影响效应进行研究.结果表明：大坝蓄水前后底栖动物群落结构发生显著变化,不同时期的群落结构差异明显.蜉蝣目稚虫对生境的剧烈变动不适应,软体动物田螺科和觹螺科的一些种类对生境的剧烈扰动较为适应,生活史较短的机会主义物种在水库淹没区和坝下河段逐渐定殖下来.建坝以及大坝的运行调度对乌江下游底栖动物的群落结构产生了重大影响,底栖动物群落结构随着时间发生一定程度的演替.在底栖动物所有类群中,软体动物对栖息地的丧失以及流量的剧烈波动具有较高的耐受性,水生昆虫相对较不耐受环境的剧烈变化,而甲壳动物的适应性极强.百分比模式相似性指数（Percent Model Affinity,PMA）的变动趋势可有效地反映大坝对底栖动物群落的影响效应,其均值随离坝距离的增加而呈现逐步增加的趋势,表明大坝调度对水生态造成的负面影响会随着离坝距离的增加而逐步弱化,这与河流不连续体理论（Serial Discontinuity Concept,SDC）的预测趋势基本一致.根据长期监测成果,蜉蝣目扁蜉科、四节蜉科、细裳蜉科以及毛翅目纹石蛾科的种群恢复状况以及PMA指数可作为评估大坝不利影响减缓措施效果的依据.  相似文献   

Analysis of the compression of structured soils using the disturbed state concept     

M. D. Liu  J. P. Carter  C. S. Desai  K. J. Xu 《国际地质力学数值与分析法杂志》2000,24(8):723-735

The aim of this note is to quantify the influence of soil structure on the compression behaviour of natural soils using the disturbed state concept (DSC). The behaviour of the fully adjusted state is chosen to be that of the corresponding soil in a reconstituted condition so that the disturbance function is a direct measure of the effects of soil structure. A new DSC compression model is proposed. This model is able to describe the compression behaviour of structured soils under loading, swelling and reloading. Special versions of the proposed model are also described for situations (a) where the compression behaviour of the corresponding reconstituted soils is linear in the e–ln p′ space and (b) where the compression is one‐dimensional. The ability of the proposed model and its various versions to describe the compression behaviour of structured soils has been verified. Copyright © 2000 John Wiley & sons, Ltd.  相似文献   

Changes in climate,vegetation cover and vegetation composition affect runoff generation in the Gulf of Guinea Basin     

Elias Nkiaka  Gloria Chinwendu Okafor 《水文研究》2024,38(3):e15124

Although considerable effort has been deployed to understand the impact of climate variability and vegetation change on runoff in major basins across Africa, such studies are scarce in the Gulf of Guinea Basin (GGB). This study combines the Budyko framework and elasticity concept along with geospatial data to fill this research gap in 44 nested sub-basins in the GGB. Annual rainfall from 1982 to 2021 show significant decreasing and increasing trends in the northern and southern parts of the GGB, respectively. Annual potential evapotranspiration (PET) also shows significant increasing trends with higher magnitudes observed in the northern parts of the GGB. Changing trends in climate variables corroborates with shift to arid and wetter conditions in the north and south, respectively. From 2000 to 2020 vegetation cover estimated using enhanced vegetation index (EVI) shows significant increasing trends in all sub-basins including those experiencing a decline in annual rainfall. Vegetation composition measured using vegetation continuous fields (VCFs) from 2000 to 2020 show an increase in tree canopy cover (TC), a decline in short vegetation cover and marginal changes in bare ground cover (BG). Elasticity coefficients show that a 10% increase in annual rainfall and PET may lead to a 33% increase and 24% decline in runoff, respectively. On the other hand, a 10% increase in EVI may lead to a 4% decline in runoff while a 10% increase in TC, SV and BG may reduce runoff by 4% and increase runoff by 3% and 2%, respectively. Even though changes are marginal, decomposing vegetation into different parameters using EVI and VCFs may lead to different hydrological effects on runoff which is one of the novelties of this study that may be used for implementing nature-based solutions. The study also demonstrates that freely available geospatial data together with analytical methods are a promising approach for understanding the impact of climate variability and vegetation change on hydrology in data-scarce regions.  相似文献   

新一轮区域规划若干问题探讨   总被引：13，自引：3，他引：10  

刘传明  曾菊新 《地理与地理信息科学》2006,22(4):56-60

对新规划理念与方法的应用、区域规划的空间尺度选择与规划重点、区域协调发展的空间管治分区与功能定位、空间发展模式的多样性选择以及各种规划间的关系如何衔接等问题进行探讨,认为新一轮区域规划应革新理念,坚持以“科学发展观”为指导思想,借鉴“反规划”方法,实行弹性规划期限;以县域规划作为基本规划单元,开展村镇小区域规划和城市群大区域规划;合理确定空间管治的分区与功能定位,选择多样性空间发展模式,完善区域规划体系,以理顺各种规划关系并提高规划的总体效用。  相似文献   

海洋科学文献中要规范使用的两组概念     

陈溥远 《海洋科学》2010,34(6):92-93

为了规范使用科学术语,根据全国科学技术名词审定委员会最新审定公布的概念内涵,并参考相关资料,对近年来在海洋科学文献中经常混用的两组概念:"抗菌活性"、"抗菌活力"、"抗菌能力";"潟湖"、"泻湖"进行了纠正,并建议有关人员在今后撰文中,注意使用规范的科学名词——"抗菌活性"和"潟湖";而勿用"抗菌活力"、"抗菌能力"和"泻湖"。  相似文献   

一种新概念潜浮平台操纵性仿真研究   总被引：1，自引：0，他引：1  

殷星杰  冯正平  易宏  李英辉 《海洋工程》2009,27(3):30-37

新概念潜浮平台是一种全新的船型,在建造实船之前对其操纵性能进行全面评估非常重要.首先在模型操纵性试验和理论分析的基础上建立考虑波浪干扰力和力矩作用的平台操纵运动数学模型,并用Simulink建立图形化的动力学仿真程序.基于该程序对水面和水下各种操纵情况进行仿真和分析,并就平台在波浪中的操纵性进行研究.仿真结果表明该平台具有良好的操纵性能,从而验证了设计,并为今后运动控制系统的设计提供了一个验证平台.  相似文献   

锋生切变型强对流概念模型在浙江中西部“3·21”过程中的应用探究          下载免费PDF全文

毛程燕  顾振海  龚理卿  孙杭媛  荆思佳 《气象科学》2023,43(3):393-401

利用ECMWF 0.25°×0.25°再分析资料,对照浙中西的强对流概念模型,对2019年3月21日发生在浙江中西部地区(简称"浙中西")的一次雷暴大风为主的强对流过程(简称"3·21"过程)进行诊断分析、经验总结。结果表明:该过程符合浙中西锋生切变型的强对流概念模型,出现该过程的环境条件是700 hPa西南急流脉动、850 hPa偏北和偏南两支气流强烈发展、地面低压倒槽和低层湿舌增强;探空曲线表现为上干下湿,对流层中层有明显的干侵入,大风指数I_w、对流有效位能 (Convective Available Potential Energy, CAPE)和500 hPa以下垂直风切变异常偏强形成动力强迫;对比不同强对流天气有不同的预报着眼点,设定阈值或可提高预报警报效率,如雷暴大风天气大风指数I_w > 18.5 m·s^-1、CAPE> 1 700 J·kg^-1、500 hPa的相对湿度小于46 %,冰雹天气则0 ℃层、-20 ℃层高度低于4.6 km和7.6 km且850 hPa与500 hPa气层温差高于26 ℃等,深刻理解该类强对流概念模型,是做好此类致灾性强对流潜势预报的关键点。  相似文献   

嵌入理论视角下的新时代国土空间规划基本框架          下载免费PDF全文

唐伟  许庆福  乔庆伟  王英  杨学作 《山东国土资源》2021,37(9)

2019年5月,《中共中央国务院关于建立国土空间规划体系并监督实施的若干意见》颁布实施,明确要求建立全国统一、责权清晰、科学高效的国土空间规划体系,整体谋划新时代国土空间开发保护格局,本文从新时代国土空间规划应遵循的基本理念入手,提出构建国土空间规划的框架的要求,深入分析多理念协调引导下的国土空间规划基本框架构建,引入地理学的"嵌入理论",提出国土空间规划"基本架构+要素嵌入"的逻辑结构,阐述了多视角的空间嵌套结构和要素嵌入的详细内容,形成了嵌入视角新时代国土空间规划逻辑框架。  相似文献