Comparison and ranking of different modelling techniques for prediction of site index in Mediterranean mountain forests

Forestry science has a long tradition of studying the relationship between stand productivity and abiotic and biotic site characteristics, such as climate, topography, soil and vegetation. Many of the early site quality modelling studies related site index to environmental variables using basic statistical methods such as linear regression. Because most ecological variables show a typical non-linear course and a non-constant variance distribution, a large fraction of the variation remained unexplained by these linear models. More recently, the development of more advanced non-parametric and machine learning methods provided opportunities to overcome these limitations. Nevertheless, these methods also have drawbacks. Due to their increasing complexity they are not only more difficult to implement and interpret, but also more vulnerable to overfitting. Especially in a context of regionalisation, this may prove to be problematic. Although many non-parametric and machine learning methods are increasingly used in applications related to forest site quality assessment, their predictive performance has only been assessed for a limited number of methods and ecosystems.In this study, five different modelling techniques are compared and evaluated, i.e. multiple linear regression (MLR), classification and regression trees (CART), boosted regression trees (BRT), generalized additive models (GAM), and artificial neural networks (ANN). Each method is used to model site index of homogeneous stands of three important tree species of the Taurus Mountains (Turkey): Pinus brutia, Pinus nigra and Cedrus libani. Site index is related to soil, vegetation and topographical variables, which are available for 167 sample plots covering all important environmental gradients in the research area. The five techniques are compared in a multi-criteria decision analysis in which different model performance measures, ecological interpretability and user-friendliness are considered as criteria.When combining these criteria, in most cases GAM is found to outperform all other techniques for modelling site index for the three species. BRT is a good alternative in case the ecological interpretability of the technique is of higher importance. When user-friendliness is more important MLR and CART are the preferred alternatives. Despite its good predictive performance, ANN is penalized for its complex, non-transparent models and big training effort.     

上海市火电行业NOx排污费征收标准及情景分析

基于火电行业典型样本的脱硝成本,以调整排污征收标准使得企业得到相对收入,即未脱硝排污费大于脱硝后总支出为判别标准,得出NOx排污征收标准最低值应为1.2元/0.95kg,最终需达到4.0元/0.95kg以上,当征收标准为1.2~10.0元/0.95kg时脱硝总支出占单位电量收入为0.5%~5.0%.根据情景分析,“十二五”征收标准为1.2元/0.95kg时5a总排污费达3.4~4.4亿元,如作为推动企业脱硝建设补贴资金来源,则可补贴额度为23~30元/kW,占实际建设支出的23.1%~30.6%,单位电量总支出占单位电量收入比例为1.5%~1.6%.“十三五”NOx排污征收标准调整为2.4元/0.95kg时5a总排污费为2.9~4.4亿元,可作为NOx超量削减奖励资金,发挥经济杠杆作用,挖掘脱硝设施减排潜力.     

辽河流域氨氮水质基准与应急标准探讨

水质基准是水质标准制/修订的科学依据,针对我国流域状况进行水质基准研究,并以此为依据制/修订我国相关水质标准已成为迫切需求.针对辽河流域的水生生物分布和水质状况,借鉴美国氨氮基准方法学,对氨氮毒性数据进行分析,得出了以水体温度和pH值为自变量的辽河流域氨氮急性和慢性基准函数方程,由方程可知,pH值8.0,25℃时,辽河流域的氨氮急性和慢性基准分别为3.06,0.364mg/L.利用荷兰和澳大利亚的水质基准技术对推算结果进行了验证和比较,结果表明3种方法得值在同一数量级,且荷兰基准技术方法相对保守.此外,基于生态风险评估对氨氮水质基准向应急水质标准的转化进行了探讨.     

基于成本核算的城镇污水处理收费标准设计研究

针对目前存在的分档计费定量依据不足等问题,基于全国第一次污染源普查数据,构建城镇污水治理投资和运行费用函数模型.计算在现有城镇污水处理成本核算体系下的东、中、西部不同污染负荷、不同排放标准的单位污水平均治理成本,将未纳入现有核算体系的管网折旧费?化验监测费用以及污泥处理费用进行成本核算,在此基础上设计一套东部?中部?西部三个地区的基于成本的污水处理收费标准体系,为城镇污水处理收费标准改革提供定量依据.     

四川省企业环境经济效益的分析评价

目前对于企业环境经济效益的分析评价,缺乏科学易行的方法。本文根据污染物排放量与经济效益间的关系,提出了单位等标污染负荷利税法,即每排放单位等标污染物所产生的年利税值。据此对四川省6个行业44家企业的环境经济效益进行了统计分析,并对其应用Excel模糊聚类进行了分级评价。结果表明:不同企业间单位等标污染负荷利税值存在多个数量级差异。造纸、纺织企业环境经济效益最差,体现了行业性弊病。制药、建材、机械电子行业企业环境经济效益整体较好,但仍有部分"粗放型"企业环境经济效益差。部分机械电子、化工企业依赖技术革新,环境经济效益优良。与定性分析评价方法相比,单位等标污染负荷利税法更能发现"高产值、高污染"下的误区,该法结合应用Excel模糊聚类分析,可简易、客观分析评价不同企业、行业甚至不同经济规模单元间的环境经济效益。     

基于空间数据的太子河河流生境分类

在文献调研的基础上,结合河流特征和专家经验确定分类使用的指标,利用DEM、河流水系等空间数据,在ArcGIS软件下提取子流域,并计算子流域内河流系统的坡降、蜿蜒度、河网密度和河流等级4个分类指标值,应用聚类分析方法对太子河河流生境进行分类,将太子河河流生境分为源头陡峭河流生境、源头弯曲河流生境、源头河流生境、支流中下游河流生境、平原支流密集河网生境、支流弯曲河流生境、干流下游生境和干流蜿蜒河流生境等8种类型,各类型河流长度在223.8~773.1km之间,其中支流弯曲河流生境最长,而干流下游生境最短. 根据各生境类型的特征,提出了我国东北地区河流生境分类的指标参考值;根据不同生境类型的河道侵蚀、水量以及多样性潜力等特征,提出了不同河流生境类型的环境管理对策.      

Groundwater quality in the major industrial area of Thessaloniki,Greece part 1: Chemical composition‐geochemical processes

Adsorption rates of Sb(V) ions on an activated alumina (AA) were analyzed by batchwise experiments, while the continuous adsorption, desorption, regeneration of AA, and multiple reuse cycles were studied by flow column tests. The adsorption rates increased quickly with the increases of shaking speed and operation temperature. The adsorbed Sb(V) ions were desorbed easily by a 50 mM NaOH solution, and a 41–90 times concentrated Sb(V) solution was yielded correspondingly. AA was effectively regenerated by desorption operation and ca. 93% of the initial adsorption capacity was retained after six times adsorption/desorption cycles.     

Acephate-induced shortening of developmental duration and early adult emergence in a nontarget insect Drosophila melanogaster

Similar to several environmental monitoring studies, the present study used Drosophila melanogaster as a model nontarget organism to explore the interfering effects of an organophosphate (OP) insecticide acephate on insect life cycle parameters. Acephate, a common OP, is readily available in nature from agricultural sources as an environmental contaminant. Along with target pests, nontarget fruit flies also suffer exposure to such environmental chemical. To evaluate the effects of such exposure, initially, acute LC₅₀ of acephate for third instar larvae was investigated and found to be between 14 and 16 μg/ml. This information yielded the following experimental concentrations (0.5, 1.5, 2.5, 3.5, 4.5, and 5.5 μg/ml) of test chemical for evaluation of effect, if any, on the insect model. Results showed that mean larval duration of insect significantly decreased on treatment with acephate, whereas the mean pupal duration remained unaffected. Interestingly the decreasing trend was seen to persist in case of mean adult emergence, where treated flies emerged significantly earlier in comparison to controls. Thus, the study demonstrated that acephate-induced shortening of developmental time and early emergence in Drosophila melanogaster.     

Modelling global-scale potential grassland changes in spatio-temporal patterns to global climate change

Grassland is one of the most widespread vegetation types worldwide and plays a significant role in global carbon cycling. Understanding the sensitivity of grassland to climate change and the effect of climate changes on the grassland ecosystems is a key issue in global carbon cycling. One of the goals of this study was to evaluate the three net primary productivity (NPP)–climate models, i.e. the Miami model, the Schuur model and the classification indices-based model. Results indicated that the classification indices-based model was the most effective model at estimating large-scale grassland NPP. In this research, changes in the spatial pattern of global potential grassland from recent past (1950–2000) to future (2001–2050) A2a scenario were analysed with the integrated orderly classification system of grassland (IOCSG) approach in a Geographic Information System (GIS) environment. NPP was evaluated with the classification indices-based model. Results indicate that under recent past climatic conditions, the main parts of global grassland are the savanna and tundra and alpine grassland and will be converted into the savanna, steppe and semi-desert grassland in A2a scenario. As a whole, areas of grassland will increase by 31.76 million hectares. The classification indices-based model estimated a 12.40% increase of total NPP in grassland from recent past to A2a scenario. It will impose a new issue for future grassland researches to support sustainable development and to provide action relevant knowledge to meet the challenge of climate change.     

航空人为差错事故/事件分析(ECAR)模型研究

为深入研究航空人为差错事故/事件的影响因素,以人为差错相关理论为基础,对比分析几种典型的人为差错分析模型;通过借鉴ECCAIRS分析框架,并在基元事件分析(EEAM)逻辑和CCAR396部的分类方法基础上,构建航空人为差错事故/事件分析(ECAR)模型,它从事件层、描述层、原因层和组织因素与改进建议层,分析航空事故和不安全事件的人为差错。此外,还将组织因素概念引入该模型。