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排序方式: 共有871条查询结果,搜索用时 187 毫秒
111.
文章是将美国经济学家A.爱伦·斯密德的SSP分析范式运用于环境保护结构绩效研究的一次新的尝试.首先指出了斯密德的SSP范式与以往环境保护绩效研究工具的不同之处,适时给出了将SSP范式运用于环境保护结构绩效分析的几个理由.最后,本文将SSP范式运用于我国体制转型时期环境保护结构绩效的分析.  相似文献   
112.
变坡度情况下森林地表上坡火行为若干特征的实验研究   总被引:9,自引:3,他引:9  
应用自行研制的“多坡段固相材料火蔓延实验台”,模拟森林地表火的蔓延过程,对变坡度情况下森林地表上坡火行为规律进行了实验研究。研究发现,上坡火火焰随坡度的变化有三种火焰类型,即小坡度的缓慢燃烧,随坡度增加的火焰的抖动以及大坡度时的贴壁剧烈燃烧。  相似文献   
113.
起爆药雷管生产中产生大量有毒废水,且其运输、贮存存在安全隐患。为克服这些困难,笔者自行制备无起爆药雷管。采用圆筒式金属内管中装填超细PETN(季戊四醇四硝酸酯),作为起爆元件,代替起爆药部分,研究装药密度对内管燃烧转爆轰(DDT)的影响。研究结果表明,在内管壁厚1~2 mm,内径Φ4.0 mm,长25 mm,装压密度为0.8~1.14 g/cm3的范围内,内管能可靠实现燃烧转爆轰。  相似文献   
114.
This paper tackles the process of energy transition from a transactional perspective. It addresses the governance of energy transition by studying its local actualizations, moving beyond purely technical and normative readings. The paper shows that through the local socio-technological energy systems, sustainability governance filters down to the level of individual, everyday behavior, thus questioning the link between public and private spaces, especially regarding the issue of housing. Going beyond the results commonly yielded by transition studies, which favor large-scale analysis, it details how the discourse of citizen involvement, which often boils down to a mere call to control one’s individual energy consumption, conceals environmental inequalities, confirming the socioeconomic divide materialized in deprived areas such as public housing estates or remote rural areas. From a methodological standpoint, the analysis is based on four case studies in Northeast France, in more or less privileged areas, and in both urban and rural environments: the renovation of a heating network in the public housing estate of Cité de l’Ill, north of Strasbourg; the solar energy systems designed for property owners in Plobsheim, a residential suburb of Strasbourg; the energy-efficient equipment set up in a public housing estate in the city of Saint-Dié, in the Vosges; and citizen participation in a cooperative program to finance wind turbines in the small Alsacian city of Saâles, in a mountain rural area. The paper draws on the results of these sociological investigations, carried out using field observations, questionnaires and interviews.  相似文献   
115.
Voluntary and active participation by a wide variety of actors is a prerequisite for successful societal transitions towards sustainability. The ‘Commitment to Sustainable Development 2050’ is a national-level initiative in Finland, aiming to mobilise a large-scale transition involving various societal actors through openly communicated commitments to concrete actions. Each commitment should focus on at least one of the eight nationally defined sustainability objectives connected to the global Sustainable Development Goals. This article assesses the implementation and the development needs of the commitment process based on a range of materials. The results highlight the importance of securing adequate resources for long-term coordination and continuous development of the commitment process, trust creation through long-term and open communication, and flexibility allowing for experimentation aimed at finding new modes of interaction between the public and private sectors.  相似文献   
116.
本文介绍了南岳森林土壤颗粒组成状况及其与环境间的关系,以及土壤的颗粒组成状况对其理化性质的影响。研究表明,南岳土壤质地主要为粉壤土、面砂土和壤粘土等。土壤质地的差异主要受植被类型、植物生长状况、放牧严重与否的影响,其次是受坡度和气候条件的影响。土壤颗粒组成状况显著地影响土壤的速效磷、速效钾、浸水容重、吸湿率、烧失率、pH值等,对土壤紧实度、有机质、碱解氮也有一定的影响。  相似文献   
117.
Efficient and sustainable management of complex forest ecosystems   总被引:1,自引:0,他引:1  
A large range of models has been developed for the analysis of optimal forest management strategies, with the well-known Faustmann models dating back to the mid-19th century. To date, however, there has been relatively little attention for the implications of complex ecosystem dynamics for optimal forest management. This paper examines the implications of irreversible ecosystem responses for efficient and sustainable forest management. The paper is built around two forest models that comprise two ecosystem components, forest cover and topsoil, the interactions between these components, and the supply of the ecosystem services ‘wood’ and ‘erosion control’. The first model represents a forest that responds in a reversible way to overharvesting. In the second model, an additional ecological process has been included and the ecosystem irreversibly collapses below certain thresholds in forest cover and topsoil depth. The paper presents a general model, and demonstrates the implications of pursuing efficient as well as sustainable forest management for the two forest ecosystems. Both fixed and variable harvesting cycles are examined. Efficient and sustainable harvesting cycles are compared, and it is shown that irreversible ecosystem behaviour reduces the possibilities to reconcile efficient and sustainable forest management through a variable harvesting cycle.  相似文献   
118.
根据我们对南岳广济寺森林群落的实地考察及其调查资料统计分析结果,发现该群落是一种尚未报道的新类型,即水丝梨+甜槠-尾叶山茶+花竹-蔓赤 车群丛(Association of Sycopsis sinensis+Castnopsis eyeri-Camellia caudata+Phyllostachys nidularia-Pellionia scabra)。该群落内有维管束植物69科116属149种;其属的区系是以热带性质成分为主,温带性质成分为辅,各占56.19%和43.81%;其种的区系成分以华夏、东亚、中国-日本和华东至华中等四种类型为主,同时本群落具有明显的华东至华中过渡交迭性质。在群落中木本植物和草本植物各占71.14%和28.86%,草本植物中的多年生和一年生类型各占22.82%和6.04%。本群落可以明显划分为乔、灌、草三个层次,每个层次又可以进一步划分为三个亚层。这一群落是中亚热带东部典型常绿阔叶林北部植被地理亚带中的常绿阔叶林,在演替过程中,群落仍将保持以水丝梨为优势种的常绿阔叶林,但其亚优势种——甜槠将可能会被多脉青冈、中华石楠、长叶石栎取代。  相似文献   
119.
Dissolved organic matter (DOM) is an important component of plant-soil systems. Its essential role in soil solution chemistry, soil-forming processes and its effects on biota, including soil fauna, bacteria, fungi and plants, is extensively documented in literature. in this contribution several forest leaf litter types are compared as sources of DOM and the released organics are subjected to gel permeation chromatography to reveal their molecular-size distribution. Moreover, complexing properties, as an indication for the podzolization potential of the litter leachates, were established. the occurrence and properties of DOM in different soil horizons were monitored beneath a stand of Scots pine. the effects of the different groups of soluble organics including phenolic, fulvic and humic acids, and of water-extractable humic substances on the performance of herbaceous plants of the forest floor are briefly reviewed.  相似文献   
120.
We present a strategy for using an empirical forest growth model to reduce uncertainty in predictions made with a physiological process-based forest ecosystem model. The uncertainty reduction is carried out via Bayesian melding, in which information from prior knowledge and a deterministic computer model is conditioned on a likelihood function. We used predictions from an empirical forest growth model G-HAT in place of field observations of aboveground net primary productivity (ANPP) in a deciduous temperate forest ecosystem. Using Bayesian melding, priors for the inputs of the process-based forest ecosystem PnET-II were propagated through the model, and likelihoods for the PnET-II output ANPP were calculated using the G-HAT predictions. Posterior distributions for ANPP and many PnET-II inputs obtained using the G-HAT predictions largely matched posteriors obtained using field data. Since empirical growth models are often more readily available than extensive field data sets, the method represents a potential gain in efficiency for reducing the uncertainty of process-based model predictions when reliable empirical models are available but high-quality data are not.  相似文献   
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