Modelling Ecological Presence–absence Data along an Environmental Gradient: Threshold Levels of the Environment

A methodology for estimating environmental thresholds of binary presence–absence data is presented where the level of the threshold is parameterised. Presence–absence data is fitted to three complementary different models: an independent null-model, a monotonically increasing or decreasing model, and an optimum model. The range of the three models is strictly between zero and one and the models are therefore well suited for modelling presence probabilities. The results of the three models may be combined by using Bayesian model selection methodologies. The proposed methodology is exemplified on observed binary presence–absence data of Bauera rubioides along an elevation gradient. Received: May 2005 / Revised: July 2005 An erratum to this article is available at.     

西双版纳热带雨林榕树种群变化与环境的关系

植物物种的多样性在生态环境保护中具有重要的地位。西双版纳热带雨林生物多样性极为丰富,是我国生物多样性研究的关键地区。榕树是热带雨林中的关键植物类群之一,关于该地区榕树种群变化与环境关系的研究结果表明：①西双版纳热带雨林内已知榕属植物有69种、变种和亚种,其中榕亚属有23个种和变种;白肉榕亚属有4个种;聚果榕亚属有2个种和变种;无花果亚属有41个种、亚种和变种;西双版纳是中国榕树种群最丰富的地区。②榕树的分布与环境有着密切的关系,榕树种类和数量以保护完好的热带原始雨林最为丰富,在该类环境中的榕以高大乔木、乔木为主;被破坏林地和次生林内的榕树种群则以小乔木、灌木、灌丛、木质藤本为主;而热带雨林环境破坏严重的地区中则以一部分先锋榕树种为主。③保护好热带雨林中的关键植物类群榕属,是保护和恢复热带雨林生态环境的重要措施之一。     

观赏果树在乌鲁木齐市绿化环境的效果及应用分析

为比较不同观赏果树在乌鲁木齐市对绿化环境的效果,分析不同观赏果树在乌鲁木齐市的应用方式.本实验以乌鲁木齐市20年生的常见观赏果树山桃、新疆梨等为实验材料,分析其可观赏性、生长期、生长状况、抗性、产量、滞尘量、绿化环境的不利因素,结果显示8种观赏果树绿化环境的效果从优往劣依次是黑桑、红果山楂、黄太平、毛杏、山桃、李子、新疆梨、葡萄.对乌鲁木齐市绿化环境的建设,这8种观赏果树与其他观赏植物配合进行花园立体绿化环境,效果更好.     

Modeling freshwater fish distributions using multiscale landscape data: A case study of six narrow range endemics

Species distribution models (SDMs) have become integral tools in scientific research and conservation planning. Despite progress in the assessment of various statistical models for use in SDMs, little has been done in way of evaluating appropriate ecological models. In this paper, we evaluate the multiscale filter framework as a suitable theoretical model for predicting freshwater fish distributions in the upper Green River system (Ohio River drainage), USA. The spatial distributions of six fishes with contrasting biogeographies were modeled using boosted regression trees and multiscale landscape data. Species biogeography did not appear to affect predictive performance and all models performed well statistically with receiver operating characteristic area under the curve (AUC) ranging from 0.87 to 0.98. Predictive maps show accurate estimations of ranges for five of six species based on historical collections. The relative influence of each type of environmental feature and spatial scale varied markedly with between species. A hierarchical effect was detected for narrowly distributed species. These species were highly influenced by soil composition at larger spatial scales and land use/land cover (LULC) patterns at more proximal scales. Conversely, LULC pattern was the most influential feature for widely distributed at all spatial scales. Using multiscale data capable of capturing hierarchical landscape influences allowed production of accurate predictive models and provided further insight into factors controlling freshwater fish distributions.     

Analysis of the relation between the cellulose,hemicellulose and lignin content and the thermal behavior of residual biomass from olive trees

The heterogeneity of biomass makes it difficult if not impossible to make sweeping generalizations concerning thermochemical treatment systems and the optimal equipment to be used in them. Chemical differences in the structural components of the biomass (cellulose, hemicellulose, and lignin) have a direct impact on its chemical reactivity. The aim of this research was to study the influence of the organic components of the raw material from olive trees (leaves, pruning residues, and wood) in the combustion behavior of this biomass, as well as to find the component responsible for the higher ash content of olive leaves. Accordingly, the study used a thermogravimetric analyzer to monitor the different states and complex transitions that occurred in the biomass as the temperature varied. The decomposition rates of the different samples were analyzed in order to establish a link between each combustion phase and the composition of the raw materials. Two methods were used to determine the hemicellulose and cellulose contents of biomass from olive trees. Significant differences among the results obtained by the different methods were observed, as well as important variations regarding the chemical composition and consequently the thermal behavior of the raw materials tested.     

Use of Community‐Composition Data to Predict the Fecundity and Abundance of Species

Abstract: Species distribution models are critical tools for the prediction of invasive species spread and conservation of biodiversity. The majority of species distribution models have been built with environmental data. Community ecology theory suggests that species co‐occurrence data could also be used to predict current and potential distributions of species. Species assemblages are the products of biotic and environmental constraints on the distribution of individual species and as a result may contain valuable information for niche modeling. We compared the predictive ability of distribution models of annual grassland plants derived from either environmental or community‐composition data. Composition‐based models were built with the presence or absence of species at a site as predictors of site quality, whereas environment‐based models were built with soil chemistry, moisture content, above‐ground biomass, and solar radiation as predictors. The reproductive output of experimentally seeded individuals of 4 species and the abundance of 100 species were used to evaluate the resulting models. Community‐composition data were the best predictors of both the site‐specific reproductive output of sown individuals and the site‐specific abundance of existing populations. Successful community‐based models were robust to omission of data on the occurrence of rare species, which suggests that even very basic survey data on the occurrence of common species may be adequate for generating such models. Our results highlight the need for increased public availability of ecological survey data to facilitate community‐based modeling at scales relevant to conservation.     

Are politicians office or policy motivated? The case of U.S. governors' environmental policies

Are elected politicians primarily motivated by holding office, thus choosing environmental policies accordingly? Or are they motivated by the chance to implement their preferred environmental policies? Do governors have character, in the sense that they promise and implement environmental policies consistent with their own preferences? To answer these questions, we study the differences in environmental spending across both re-electable and lame duck governors from the two main political parties. In our empirical analysis, we make use of parametric and non-parametric regression-discontinuity approaches. While re-electable governors do not set significantly different policies, lame duck governors do. We argue that in the area of environmental policy governors appear to be primarily office motivated and lack character.     

现代统计信息分析技术在安全工程方面的应用——因子分析

因子分析是一种多元统计分析方法。因子分析的主要功能是寻求隐藏在观测数据背后,支配变量的公因子,以最简单的形式表达事物的本质概念。文中介绍了因子分析的计算方法。     

试论安全生产中的几个关系

近年来 ,我国国民经济快速发展 ,但安全生产状况不容乐观 ,安全事故频繁发生 ,事故死亡人数居高不下。笔者在对 1993～ 2 0 0 0年我国安全生产数据进行分析的基础上 ,应用最小二乘法拟合技术研究安全生产与安全事故的内在联系 ;建立人均GDP、人均安全投入、人均安措投入、人均劳保投入与 10万人死亡率和亿元GDP死亡率的函数关系 ;探讨造成安全生产事故的原因 ;进一步完善了安全理论。上述对安全生产中若干问题研究的思路和方法 ,为安全生产的宏观决策和预防事故的发生提供了重要理论和科学依据。     

许昌市浅层地下水中离子总量与电导率间关系的研究

通过实验,用回归分析法,研究了许昌市浅层地下水中离子总量与电导率间的定量关系,可用电导法快速了解水质中的离子总量和衡量水质全分析中主要被测离子总和的质量.