Cause-effect relationships in analytical surveys: an illustration of statistical issues

Establishing cause-effect is critical in the field of natural resources where one may want to know the impact of management practices, wildfires, drought, etc. on water quality and quantity, wildlife, growth and survival of desirable trees for timber production, etc. Yet, key obstacles exist when trying to establish cause-effect in such contexts. Issues involved with identifying a causal hypothesis, and conditions needed to estimate a causal effect or to establish cause-effect are considered. Ideally one conducts an experiment and follows with a survey, or vice versa. In an experiment, the population of inference may be quite limited and in surveys, the probability distribution of treatment assignments is generally unknown and, if not accounted for, can cause serious errors when estimating causal effects. The latter is illustrated in simulation experiments of artificially generated forest populations using annual plot mortality as the response, drought as the cause, and age as a covariate that is correlated with mortality. We also consider the role of a vague unobservable covariate such as `drought susceptibility'. Recommendations are made designed to maximize the possibility of identifying cause-effect relationships in large-scale natural resources surveys.     

电除尘器中离子风对除尘效果的影响

目的研究电除尘器中离子风对除尘过程的影响。方法分析电除尘器中离子风对除尘效果的影响,建立完整的颗粒荷电模型,在Fluent软件平台上进行计算。结果离子风在电极线附近呈双螺旋结构,正对电极线位置的离子风速度最大,在远离电极线的方向上逐渐变小,越靠近电极线,速度下降的梯度越大,对流场有扰动作用,随流速增加,离子风效应被逐渐削弱。当主流速小于等于0.5 m/s时,离子风体现为增大驱进速度,颗粒更快到达极板,有利于改善除尘效率。结论电极线的偏置可以提高除尘效率,当电极线置于电场宽度方向1/4处时,可以获得最佳除尘效果。     

Side biases in humans (Homo sapiens): three ecological studies on hemispheric asymmetries

Hemispheric asymmetries and side biases have been studied in humans mostly in laboratory settings, and evidence obtained in naturalistic settings is scarce. We here report the results of three studies on human ear preference observed during social interactions in noisy environments, i.e., discotheques. In the first study, a spontaneous right-ear preference was observed during linguistic exchange between interacting individuals. This lateral bias was confirmed in a quasi-experimental study in which a confederate experimenter evoked an ear-orienting response in bystanders, under the pretext of approaching them with a whispered request. In the last study, subjects showed a greater proneness to meet an experimenter’s request when it was directly addressed to the right rather than the left ear. Our findings are in agreement both with laboratory studies on hemispheric lateralization for language and approach/avoidance behavior in humans and with animal research. The present work is one of the few studies demonstrating the natural expression of hemispheric asymmetries, showing their effect in everyday human behavior.     

A population comparison of the strength and persistence of innate colour preference and learning speed in the bumblebee <Emphasis Type="Italic">Bombus terrestris</Emphasis>

Studies of innate colour preference and learning ability have focused on differences at the species level, rather than variation among populations of a single species. Initial strength and persistence of colour preferences are likely to affect colour choices of naïve flower visitors. We therefore study the influence of both the strength and persistence of innate colour preference (for blue) on an operant learning task (associating food reward with yellow flowers) in two populations of the bumblebee Bombus terrestris. We found that both strength and persistence of blue preference differed significantly between populations: B. terrestris dalmatinus had a weaker and less persistent blue preference than B. terrestris audax. These differences in preference also influenced learning performance. Considering only landing behaviours, one-trial learning occurred in the majority (73%) of bees, and was achieved sooner in B. terrestris dalmatinus because of its weaker blue preference. However, compared to landing behaviours the relative frequency of approach flights to rewarding and unrewarding flower types changed more slowly with task experience in both populations. When considering both approaches and landings, the rate of learning, following the first rewarded learning trial, was faster in B. terrestris audax than B. terrestris dalmatinus. However, the net effects of population differences in blue preference and learning dynamics result in similar final levels of task performance. Our results provide new evidence of behavioural differences among isolated populations within a single species, and raise intriguing questions about the ecological significance and adaptive nature of colour preference.     

不同施工顺序对陡坡偏压小净距隧道围岩稳定性的影响研究

为了研究陡坡偏压条件下不同施工顺序对小净距隧道围岩稳定性的影响,结合工 程实例,考虑“先浅后深”与“先深后浅”两种施工顺序,通过有限元软件ABAQUS建立 三维弹塑性分析模型进行了施工全过程数值模拟,重点分析了不同施工顺序对地表边坡 、拱圈特征点围岩以及中夹岩柱的影响,并计算了不同施工顺序下的隧道开挖安全系数 。结果表明:先施工深埋侧隧道会加剧围岩整体偏压效应,并会对中夹岩柱处围岩产生 往返的扰动,不利于围岩稳定性的控制,且先开挖浅埋侧隧道的安全性高于先开挖深埋 侧隧道。     

Correcting for non-response bias in contingent valuation surveys concerning environmental non-market goods: an empirical investigation using an online panel

Data collection for economic valuation by using Internet surveys and pre-recruited Internet panels can be associated with severe disadvantages. Problems concerning sample coverage and sample representativeness can be expected. Representation errors may occur since people can choose whether to be part of an Internet panel and subsequently whether they wish to participate in the survey, thereby introducing two elements of potential self-selection. These elements may be correlated with preferences, thus making the respondents a non-random and non-representative sample, ultimately biasing results. This paper analyses a sample used for an Internet contingent valuation method survey eliciting preferences for improvements in water quality of a river. We find that some variables that affect the survey participation decision also affect willingness-to-pay, consequently biasing our welfare estimates. We show how adjusting willingness-to-pay for this bias can be accomplished by using a grouped data model incorporating a correlation parameter to account for selection.     

Inter-observer variation in habitat survey data: investigating the consequences for professional practice

Environmental assessments and land-use planning require reliable information on the botanical composition and distribution of habitats. There have been numerous academic studies of inter-observer variation in species-inventory and habitat mapping, but studies addressing the prevalence of inter-observer variation and consequences of poor quality data in professional practice are lacking. This paper addresses these questions via a questionnaire survey of environmental professionals, using the standard Phase 1 and National Vegetation Classification (NVC) survey methods in the United Kingdom. The survey revealed that misidentification of habitat types within survey reports was relatively common (approximating to 20% of all reports seen by respondents over the previous five years). Approximately 40% of respondents who had encountered erroneous reports stated that these had led to inaccurate initial site ecological assessments. Additional field surveys and discussions with surveyors were commonly used to resolve these issues, but for Phase 1 and NVC 26% and 34% of respondents, respectively, had encountered one or more cases where errors resulted in negative consequences for clients commissioning surveys (in terms of extra costs and project delays). Net loss of biodiversity arising from inaccurate reports was reported in at least one instance by 32% and 38% of respondents for Phase 1 and NVC surveys, respectively – results that may contribute to the attrition of natural capital within the UK. The study highlights the need to extend studies of inter-observer variation to consider impacts on environmental assessments and decision-making in professional practice. The potential benefits of introducing an accreditation scheme (favoured by the majority of respondents to the questionnaire) are discussed.     

Avoidance test with Enchytraeus albidus (Enchytraeidae): effects of different exposure time and soil properties

Enchytraeids are ecologically relevant soil species and are commonly used in standardized toxicity tests. Their rapid reaction to a chemical exposure can be used as a toxicological measurement endpoint that assesses the avoidance behavior. The objectives of this investigation were to determine the effects of soil properties on the avoidance behavior of Enchytraeus albidus and to optimize the duration of avoidance test. The avoidance tests included (1) exposures in OECD artificial soil with standard or modified properties (pH, clay or peat content), and (2) exposures to copper chloride, cadmium chloride, and to the organic pesticides dimethoate and phenmedipham for different time periods. Results showed that alteration of OECD soil constituents significantly affected the avoidance behavior of enchytraeids, and that the 48-h exposure was the optimal duration of the test. Consideration of soil properties is important for selecting appropriate experimental design and interpreting the results of the enchytraeid avoidance test.     

基于危险化学品储存的区域生态环境风险评价

借鉴现有的生态风险评价方法,提出适合危险化学品储存的区域生态风险评价体系,即区域生态风险受体确定,评价终点选择,暴露途径和方式,暴露剂量分析与计算,风险表征以及区域生态风险管理对策等。研究结果表明:在有风模式中,鸟类的不可接受风险范围最远可达下风向7km,蛙类的不可接受风险最远可达下风向27km。大部分敏感点的蛙类急性暴露剂量都超标,处于不可接受风险水平;80%的敏感点的鸟类处于不可接受风险水平。根据风险评价结果,提出从防范措施、应急预案、环境监测和生态补偿4个方面制定区域生态风险管理措施。该区域生态环境风险评价研究为同类型区域生态环境风险评价提供借鉴作用。     

化学氧化法处理资源回收后的J-酸和吐氏酸染料中间体废液

萘系磺酸染料中间体Ｊ－酸和吐氏酸废母液经有用资源的回收后,尚须进行最终出水的达标处理．通过吐氏酸和Ｊ－酸废母液萃余液的后处理试验,确定了盐回收－混凝沉淀－化学氧化的达标处理工艺方案,并确定了相应的工艺参数．其中化学氧化采用Ｆｅｎｔｏｎ试剂（以双氧水作氧化剂,绿矾为催化剂）,在经济合理的投量范围内经２—４ｈ反应,萃余液ＣＯＤＣｒ去除率达８０％以上,最终出水ＣＯＤｃｒ在２００ｍｇ／Ｌ以下,满足有关工业废水排放标准．