北京翠湖湿地水环境恢复效果     

李伟  崔丽娟  赵欣胜  张曼胤  王义飞  商晓静 《湿地科学与管理》2014,(3):53-56

2010年、20111年和2012年7月对北京翠湖湿地水环境进行跟踪调查与监测,评估湿地恢复之后翠湖湿地水环境的改善效果。恢复区水体pH值、总氮(TN)、总磷(TP)、电导率(EC)和溶解氧(DO)等指标在3年间都表现为下降趋势。其中,pH值从2010年的8.36降到2012年的7.44;TN从2010年的1.94 mg/L降到2012年的1.76 mg/L;TP从2010年的0.129 mg/L降到2012年的0.117 mg/L。说明翠湖湿地经过湿地恢复后,总氮(TN)、总磷(TP)去除效果明显,湿地水环境良好改善,水体自净能力得到加强。本研究可为湿地水环境恢复评估及管理提供一定的科学依据。  相似文献   

宁化县紫色土侵蚀区治理年限对不同治理模式植物多样性的影响     

谭建金  陈松林  禤虹杏  黄锦祥  廖善刚 《亚热带资源与环境学报》2014,(4):36-43

以宁化县紫色土侵蚀区4种主要治理模式的植物群落调查资料为基础,采用丰富度指数、均匀度指数和多样性指数对其进行分析。研究结果表明：1）与对照区相比,各治理样地植物群落物种多样性、丰富度和均匀度指数均有不同程度提高,植物群落结构趋于复杂稳定。2）随着演替的进展,群落多样性指数在乔灌草混交及封禁治理模式增大,但在油茶园改造模式中变化不明显。3）经济林模式治理年限短,受人为干扰强烈,植物多样性差异较大,其随治理年限的变化有待于进一步观察。4）植物多样性与植物生长型的关系：物种丰富度和多样性指数在治理初期为草本层大于灌木层,随着群落演替的进展,灌木层逐渐大于草本层;均匀度指数的变化,在油茶园改造及乔灌草混交模式中草本层大于灌木层,而在经济林和封禁模式中,多表现为灌木层大于草本层。因此,后续治理应注意：侵蚀劣地的生态恢复必须进行科学的人为干预,生物措施应合理配置乔灌草物种数和个体数,对树种单一的群落需进行补植修复;针对不同治理阶段和治理模式,生态恢复侧重点要有差异。  相似文献   

日本福岛7.3级地震灾害损失总结与讨论          下载免费PDF全文

陈相兆  张桂欣  孙柏涛  武继双  陈洪富 《世界地震工程》2021,(2):058-65

2021年2月13日,日本本州东岸近海发生7.3级地震,没有造成人员死亡,仅150余人受伤,导致建筑物和基础设施发生不同程度的破坏和功能中断。此次强震并未造成大量的人员伤亡和工程结构本体破坏,但出现非结构构件破坏较为普遍以及基础设施功能中断的情况。介绍了各机构的震后灾害损失快速评估工作,总结了工程结构破坏和功能影响、人员伤亡和经济损失情况。对此次地震的灾害特征进行了总结和思考,认为随着各地区抗震能力的提高,非结构构件破坏、地震灾害链、基础设施功能中断与恢复、抗震韧性将成为今后研究的重点。  相似文献   

Seepage mechanisms and permeability differences between loess and paleosols in the critical zone of the Loess Plateau     

Kai Hou  Hui Qian  Yuting Zhang  Haike Wang 《地球表面变化过程与地形》2021,46(10):2044-2059

The soil in the Loess Plateau has special permeability characteristics due to the alternating distribution of loess and paleosol layers. Using an analysis of the physical properties, microstructure and thermogravimetric analysis of loess and paleosol, this paper examines strata seepage mechanisms in the loess tableland area and considers the applicability of a hydraulic conductivity empirical formula. The analysis shows that hydraulic conductivity attenuation with depth can be represented by a negative exponential model, while hydraulic conductivity values are not normally distributed. The best-fitting models of hydraulic conductivity in the horizontal (K_H) and vertical (K_V) directions are Gaussian models, and both have strong spatial correlations. This study of the difference in permeability between loess and paleosol found that the depositional environment was the dominant causal factor, making the average hydraulic conductivity of most loess layers greater than that of the underlying paleosol layers. Different microstructures between loess and paleosol also confirmed the microscopic explanation in permeability anisotropy and their permeability difference. Thermogravimetric analysis determined temperature ranges for different types of water lost by heat, and then calculated ratios of bound water mass to liquid limit, with an average of 0.768. A modified formula suitable for loess was obtained by integrating the consistency index method and effective porosity ratio model into the hydraulic conductivity empirical formula. Compared with the results of laboratory tests and uncorrected formulas, the modified formula provides a good estimate of strata hydraulic conductivity. Accurate understandings of seepage mechanisms and permeability differences in the loess area are important, promoting ecological restoration and providing scientific guidance for the sustainable development of the Loess Plateau.  相似文献   

A dynamic riparian forest structure model for predicting large wood inputs to meandering rivers     

John C. Stella  Li Kui  Gregory H. Golet  Frank Poulsen 《地球表面变化过程与地形》2021,46(15):3175-3193

Fluvial processes strongly influence riparian forests through rapid and predictable shifts in dominant species, tree density and size that occur in the decades following large floods. Modelling riparian forest characteristics based on the age and evolution of floodplains is useful in predicting ecosystem functions that depend on the size and density of trees, including large wood delivered to river channels, forest biomass and habitat quality. We developed a dynamic model of riparian forest structure that predicts changes in tree size and density using floodplain age derived from air photos and historical maps. Using field data and a riparian forest chronosequence for the 160-km middle reach of the Sacramento River (California, USA), we fit Weibull diameter distributions with time-varying parameters to the empirical data. Species were stratified into early and late successional groups, each with time-varying functions of tree density and diameter distributions. From these, we modelled how the number and size of trees in a stand changed throughout forest succession, and evaluated the goodness-of-fit of model predictions. Model outputs for the early successional group, composed primarily of cottonwoods and willows, accounted for most of the stand basal area and large trees >10 cm DBH for the first 50 years. Post-pioneer species with slower growth had initially low densities that increased slowly from the time of floodplain creation. Within the first 100 years, early successional trees contributed the most large wood that could influence fluvial processes, carbon storage, and instream habitat. We applied the model to evaluate the potential large wood inputs to the middle Sacramento River under a range of historical bank migration rates. Going forward, this modelling approach can be used to predict how riparian forest structure and other ecosystem benefits such as carbon sequestration and habitat quality respond to different river management and restoration actions.  相似文献   

The nappe structure of the central Northern Calcareous Alps and its disintegration during Miocene tectonic extrusion—a contribution to understanding the orogenic evolution of the Eastern Alps     

W.?FrischEmail author  H.-J.?Gawlick 《International Journal of Earth Sciences》2003,92(5):712-727

The classical concept of the nappe structure of the central Northern Calcareous Alps (NCA) is in contradiction with modern stratigraphic, structural, metamorphic and geochronological data. We first perform a palinspastic restoration for the time before Miocene lateral tectonic extrusion, which shows good continuity of structures, facies and diagenetic/metamorphic zones. We present a new nappe concept, in which the Tirolic unit practically takes the whole area of the central NCA and is divided into three subunits (nappes): Lower and Upper Tirolic subunit, separated by the Upper Jurassic Trattberg Thrust, and the metamorphic Ultra-Tirolic unit. The Hallstatt (Iuvavic) nappe(s) formed the highest unit, but were completely destroyed by erosion after nappe stacking. Remnants of the Hallstatt nappes are only represented by components of up to 1 km in size in Middle/Upper Jurassic radiolaritic wildflysch sediments ("Hallstatt Mélange" belonging to the Tirolic unit). Destruction of the continental margin started in Middle to Upper Jurassic time and prograded from the oceanic side towards the shelf. The original substratum of the external nappes (Bavaric units) of the NCA was largely the Austroalpine crystalline basement, of the internal nappes (Tirolic units) the weakly metamorphosed Palaeozoic sequences (Greywacke Zone and equivalents). Eocene movements caused limited internal deformation in the Tirolic unit.  相似文献   

高能天文中成像和解谱的直接方法     

李惕碚  吴枚 《中国天文和天体物理学报》1993,(3)

本文提出了用迭代计算直接解成像方程以复原图像的方法.同一方法可应用于一维谱形复原.迭代中应用合理的约束条件对过程进行非线性控制.用拟合技术处理成像方程抑制噪声和提高分析灵敏度.对蒙特卡罗样本和空间高能天文实测数据的分析都显示出直接方法比传统的成像法灵敏度高、分辨能力好,可以同时显示对象的弥散和分立结构,能用于统计性更差的观测数据.直接方法原则上可以应用于其它领域各种类型的图像和谱形复原工作.  相似文献   

THE USE OF A RATIO METHOD AS AN ALTERNATIVE TO CONSTRAINED DECONVOLUTION     

PAUL BENJAMIN CRIEEY The University of Tennessee Knoxville  Department of Electrical  Computer Engineering  Ferris Hall  Knoxville  TN -  U.S.A. 《地理学报(英文版)》1991,(2)

This paper will consider the use of an iterative ratio technique called Gold's ratio method as an alternativeto iterative constrained deconvolution methods for the restoration of overlapped and noisychromatograpic peaks.The study will consist of first describing the technique and then evaluating itsperformance with respect to Jansson's deconvolution procedure.A Hewlett-Packard 5890A gaschromatograph will be used to generate most of the test data.The evaluation criteria will includeconvergence rates,peak area errors and variances,retention time variances and noise performance.  相似文献   

露天矿区土地复垦及生态重建数据库的设计与实现   总被引：1，自引：0，他引：1  

师华定  王立  白中科 《地球信息科学学报》2005,7(4):81-85

矿区土地复垦与生态重建研究以及复垦模式的验证、推广,都需要借助数据库技术对多年研究数据进行有效的组织管理。本文论述了土地复垦与生态重建数据库设计过程中的用户需求分析、概念结构设计、逻辑结构设计、物理结构设计以及数据库的实施与维护。该研究促进了矿区土地复垦与生态重建工作的信息化。  相似文献   

Ecosystem scale evapotranspiration and net CO2 exchange from a restored peatland     

Richard M. Petrone  J. M. Waddington  Jonathan S. Price 《水文研究》2001,15(14):2839-2845

An understanding of the symbiotic water and gas exchange processes at the ecosystem scale is essential to the development of appropriate restoration plans of extracted peatlands. This paper presents ecosystem scale measurements of the atmospheric exchange of water and carbon dioxide (CO₂) from a restored vacuum extracted peatland in eastern Québec, utilizing full‐scale micrometeorological measurements of both evaporation and CO₂. The results indicate that the adopted restoration practices reduce the loss of water from the peat, but CO₂ emissions are ～25% greater than an adjacent nonrestored comparison site. The blockage of drainage ditches and the existence of a mulch cover at the site keep the moisture conditions more or less constant. Consequently, the CO₂ flux, which is predominantly soil respiration, is strongly controlled by peat temperature fluctuations. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献