市民与城市林业

今天,美国许多林业工作者正在研究城市林业。城市居民和社会团体每天都要接触都市环境,管理和使用城市林业资源,因此,城市林业与市民的关系是非常密切的。其相互作用也是非常重要的。 城市林业资源的管理和使用与普通林业有广泛地联系,有时,市民们是直接按普通林业的方式来管理城市林业的。 本文论述了在城市环境中,市民与城市林业的关系、说明了城市林业的多种效益、提出了与城市林业有关的一些论点。     

Isolating the impact of sediment toxicity in urban streams

Several factors can contribute to the ecological degradation of stream catchments following urbanization, but it is often difficult to separate their relative importance. We isolated the impact of polluted sediment on the condition of an urban stream in Melbourne, Australia, using two complementary approaches. Using a rapid bioassessment approach, indices of stream condition were calculated based on macroinvertebrate field surveys. Urban stream reaches supported impoverished macroinvertebrate communities, and contained potentially toxic concentrations of heavy metals and hydrocarbons. Using a field microcosm approach, a bioassay was carried out to assess sediment pollution effects on native macroinvertebrates. Sediment from urban sites substantially altered the microcosm macroinvertebrate community, most likely due to elevated heavy metal and hydrocarbon concentrations. Macroinvertebrate surveys combined with a bioassay approach based on field microcosms can help isolate the effect of stream pollutants in degraded ecosystems.     

中国经济系统地震易损性分析

本文分析了地震对经济系统功能的破坏。在现有数据的基础上建立了一个经济模型，用于定量分析地震对经济的破坏。并进一步提出了一个动态区域经济模型的原理和基本结构，当数据条件具备即可建立模型。这样一个动态模型可确切地描述地震对经济系统的破坏及破坏后的恢复过程。     

关于美国城市环境管理的启示

城市环境管理是我国环保工作的重点之一,美国城市环境管理中的经验和教训,可以为我们提供一些借鉴。     

四川瓦屋山原生和次生常绿阔叶林的群落学特征

利用野外调查资料，比较分析了瓦屋山中山段（halt 1500-1900m)自然恢复的次生和原生常绿阔叶林的群落外貌，群落主要乔木物种组成，高度和径阶结构等特征。结果表明：（1）恢复42a的次生常绿阔叶林已基本形成中亚热带湿性绿阔叶的生活型外貌和以中小型单叶为主，草质叶明显的特征，但与原生的中亚热带湿性常绿阔叶林相比，落叶的中小矮高位芽植物明显较多，地面芽和地下芽植物偏少；（2）次生常绿阔叶林乔木层树种有67种，而原生林仅57种，次生和原生常绿阔叶林乔木层主要优势物种组成相似，但次生林优势种更明显，并存在较多的处于伴生状态（局部地段还居于优势地位）的落叶乔木种类；（3）次生林较相同面积上的原生林乔木层的平均胸径DBH＜2.9cm。次生林具有小径阶个体多，大径阶个体少的明显特点，但两类森林乔木大小结构分布与其它地区的异龄林基本一致，均遵从指数分布关系；（4）次生林6400m^2内h≥3m的乔木有1199株。垂直高度h分化不明显，hmax=22.8m,hav仅9.7m，而原生林6400m^2内h≥3m的乔木有1045株，平均高度12.8m。次生林缺失Ⅶ高度级（＞25m)，而Ⅵ高度级仅8株（原生林有55株），低高度级（Ⅱ-Ⅳ级）株数的比例大，占总株数的87．12％。说明次生林乔木拥挤度大，乔木层个体正竞争强烈，群落处于不稳定的发展阶段，其进一步发展必将发生乔木自疏和它疏过程；（5）次生与原生林群落学特征比较表明，严重破坏后42a来通过封山育林自然恢复的次生林已经恢复常绿阔叶林的群落外貌，已经具有了原生常绿阔叶林群落结构特征，到达了常绿阔叶林阶段，自然恢复是迅速而成功的。研究发现，自然恢复是生态恢复重建的可行性途径之一，而群落外貌（生活型、叶型谱）、主要树种组成，群落结构很好地说明了常绿阔叶林破坏后的恢复状况是良好的，因些这些指标可以作为森林恢复评价的可选指标。图2表4参35     

Improving suitability of urban canals and canalized rivers for transportation,thermal energy extraction and recreation in two European delta cities

Canals and canalized rivers form a major part of surface water systems in European delta cities and societal ambitions to use these waters increase. This is the first assessment of how suitability of these waters can improve for three important uses: transportation, thermal energy extraction (TEE) and recreation. We assess suitability with Suitability Indices (SIs) and identify which alterations in the water system are needed to improve SI scores in Amsterdam, The Netherlands, and Ghent, Belgium. The results show spatial variability in suitability scores. Current suitability for transportation is low (SI score = 1) to excellent (SI score = 4), for TEE fair (SI score = 2) to excellent (SI score = 4), and suitability for recreation is low (SI score = 1). Suitability could improve by enlarging specific waterway dimensions, increasing discharge and clarity, and by enhancing microbiological water quality. The same methodology can be applied to optimize designs for new water bodies and for more water uses.Supplementary InformationThe online version contains supplementary material available at 10.1007/s13280-022-01759-3.     

Effects of habitat and landscape fragmentation on humans and biodiversity in densely populated landscapes

Landscape fragmentation has often been seen as an only ecological problem. However, fragmentation also has a societal perspective, namely, in how humans perceive landscape fragmentation and in how landscape fragmentation potentially influences human well-being. These latter aspects have rarely been addressed so far. The inter-relationship of ecological and human dimensions of landscape fragmentation becomes especially evident when looking at the landscape where most people in industrial countries live, namely in suburban and urban areas. In these areas, landscape planners and environmental managers are confronted with the problem that landscapes should fullfil various functions, often with conflicting goals, e.g. nature reserves to enhance species richness vs. recreational areas for city-dwellers. We reviewed the ecological and sociological literature relevant for fragmentation in suburban and urban landscapes. In an interdisciplinary approach, we evaluated whether there are similarities and dissimilarities between the ecological and the human aspects of landscape fragmentation. We found important similarities. An example is that for both, humans and biodiversity, the loss of semi-natural areas has more drastic effects than the fragmentation of these areas per se. However, there are also relevant differences. We concluded that in densely populated landscapes a shift from responsive planning to an intentional design of environments is therefore needed.     

浅议城市矿产示范基地建设的融资途径

针对发展循环经济的重点领域中的热点话题,在密切关注国家相关政策走向并结合本地区实际的基础上,通过开展＂城市矿产＂示范基地建设项目前期工作,探索性地提出了资源再生利用规模化发展的建设项目融资途径,并简述了政府推进循环经济发展的相关政策措施。     

城市交通系统抗灾变研究进展

在总结城市交通系统抗灾变问题及其特点的基础上,综述了城市交通抗灾变研究的国内外进展,并对该问题的研究方向进行了分析.     

重庆城市电网工频电磁环境现状及安全性分析

在现场实测的基础上,分析研究了重庆城市电网中各种电压等级、各种类型变电站周边环境,多种形式架空线路下方区域以及地下电缆周围工频电磁环境的现状,对比国家现行标准限值,评价重庆城市电网的工频电磁环境的安全性,同时也指出随着架空线密度的增加,周围工频电场不但不增加,反而有降低的现象.目前擅自在输电线路下建房或增加房屋高度是危及电磁环境安全的主要问题,应加大监管力度,减少日后不必要的环保纠纷.