Comparing discriminant analysis, neural networks and logistic regression for predicting species distributions: a case study with a Himalayan river bird

We assessed the occurrence of a common river bird, the Plumbeous Redstart Rhyacornis fuliginosus, along 180 independent streams in the Indian and Nepali Himalaya. We then compared the performance of multiple discrimant analysis (MDA), logistic regression (LR) and artificial neural networks (ANN) in predicting this species’ presence or absence from 32 variables describing stream altitude, slope, habitat structure, chemistry and invertebrate abundance. Using the entire data (=training set) and a threshold for accepting presence in ANN and LR set to P≥0.5, ANN correctly classified marginally more cases (88%) than either LR (83%) or MDA (84%). Model performance was assessed from two methods of data partitioning. In a ‘leave-one-out’ approach, LR correctly predicted more cases (82%) than MDA (73%) or ANN (69%). However, in a holdout procedure, all the methods performed similarly (73–75%). All methods predicted true absence (i.e. specificity in holdout: 81–85%) better than true presence (i.e. sensitivity: 57–60%). These effects reflect species’ prevalence (=frequency of occurrence), but are seldom considered in distribution modelling. Despite occurring at only 36% of the sites, Plumbeous Redstarts are one of the most common Himalayan river birds, and problems will be greater with less common species. Both LR and ANN require an arbitrary threshold probability (often P=0.5) at which to accept species presence from model prediction. Simulations involving varied prevalence revealed that LR was particularly sensitive to threshold effects. ROC plots (received operating characteristic) were therefore used to compare model performance on test data at a range of thresholds; LR always outperformed ANN. This case study supports the need to test species’ distribution models with independent data, and to use a range of criteria in assessing model performance. ANN do not yet have major advantages over conventional multivariate methods for assessing bird distributions. LR and MDA were both more efficient in the use of computer time than ANN, and also more straightforward in providing testable hypotheses about environmental effects on occurrence. However, LR was apparently subject to chance significant effects from explanatory variables, emphasising the well-known risks of models based purely on correlative data.     

Winter bird use of seed-rich habitats in agri-environment schemes

To assess the effectiveness of over-winter seed provision by agri-environment schemes, bird use of patches of seed-bearing crops was compared with that of other seed-rich habitats on 53 farms in eastern Scotland over three winters. Seed-bearing crops were the most frequently selected habitat, and held 28% of birds of the 10 species recorded. Outside schemes, cereal stubble was the most selected habitat and held 44% of birds. For nine species, seed-bearing crops were used by more birds than expected from the area of crop available in at least one winter, and five species were more likely to occur in first-winter patches, reflecting a greater abundance of cereal grain than in second-winter patches. For cereal grain specialists such as buntings, sowing cereal-based crops annually would ensure that grain is available in each winter, whilst either a 1-year or a 2-year crop would be appropriate for finches that favour oilseeds, and species with a more generalist diet.     

Field-breeding birds on organic and conventional arable farms in the Netherlands

In this study territory densities of field-breeding farmland birds were compared on pairwise-selected organic and conventional arable farms for two years. Differences in territory densities between the two farm types were explained examining the effects of three factors on territory densities: (1) non-crop habitats, (2) crop types and (3) within-crop factors. In both years, densities of most species did not differ between organic and conventional farms. Only skylark and lapwing were more abundant on organic farms, but only skylarks showed a consistent pattern over both years. Differences in crop types grown between the two systems were the only explaining factor for differences in densities of skylark. For lapwing, the difference was only partly due to differences in crop type, but differences in within-crop factors (probably as a result of crop management) were likely to have had an effect as well. There were no significant differences in abundance of non-crop habitats between the two farming systems, so this could not explain differences in territory densities.     

“冰冻灾害”过程中长途汽车司机心理安全感与应付方式的初步调查

“春季冰灾”的严重后果无疑是“京珠高速”的瘫痪,而长时间滞留其中的长途汽车司机既是灾害当事人,也是灾害见证人。在灾害持续过程中了解当事人心理活动及其变化过程,在灾害心理学上无疑具有理论意义与实践价值。调查结果表明,灾害持续时间（车辆滞留时间）与当事人的心理活动有着密切的关系,灾害持续一周后,当事人的心理安全感显著下降,应付方式开始从成熟型应对向不成熟型应对退化。看来,灾害持续不仅消解心理健康,而且瓦解应变能力。     

城市绿地结构与鸟类栖息生境的营造

城市化对城市鸟类多样性产生了诸多不利影响。城市绿地结构是鸟类栖息生境选择的重要因素之一。在分析公园面积、连通性、岛屿化等影响城市鸟类多样性的城市绿地结构特征基础上,提出通过优化绿地结构营造鸟类栖息生境的原则,探讨了保护城市自然保留地、建设环城绿化带、构建河岸带与道路绿色廊道、复层植物群落配置、特殊空间绿化等途径作为鸟类生境营造的方法。     

农民工大规模外出的经济增长效应研究

农民工大规模外出的影响和作用十分复杂.利用反设事实法,并运用Cobb-Douglas生产函数,分析了湖南省2001-2011年经济增长过程中资本投入、劳动投入和技术进步的贡献,并对于湖南省2001-2011年潜在经济增长进行了进一步推断.研究结果:如果不存在出省打工的数百万农民工,同期湖南将实现净增长428％,年均经济增长率18.10％,比现实经济增长率高出0.5个百分点.这表明农民工大规模外出尽管带来了可观的劳务收入,但也使得流出地区实际经济总量低于其可能的潜在总量,导致其实际经济增长率低于其潜在经济增长率,从而也间接证明了农民工大规模出省打工对于农民工流出地区的经济增长具有一定抑制作用.地方政府在将发展“劳务经济”作为发展战略的同时,还应认识到,“劳务经济”发展战略在带来较多劳务收入的同时,也会在一定程度上削弱地方社会经济的发展潜力.当前不宜将农村剩余劳动力转移作为对各级地方政府目标责任考核内容.     

农民工职业危害防护需求意愿调查分析

为了调查农民工职业危害防护的具体需求意愿及他们对企业职业危害管理现状的认知,分析农民工职业危害防护需求意愿与农民工职业危害防护行为之间的关系。采用问卷调查的定量调查方法进行调查。调查对象中男性农民工409人,女性农民工157人。参与问卷调查的农民工,均接触一种及以上的职业性有害因素。调查内容包括了解公司预防和控制职业病的政策,参与公司的职业危害管理决策,实施的职业性健康安全培训、健康监护、个人防护用品的使用等预防和控制职业病的管理措施等方面,本次调查显示,农民工对于预防职业危害表现出强烈的需求愿望,且对企业的职业危害防护现况表示了不满,倾向于采取极端的行为维护自身的健康权益。但另一方面,农民工实际参与企业职业危害防护的行为率较低,与他们的需求意愿相比有明显的差距。     

鄱阳湖湿地候鸟栖息地微塑料污染特征

微塑料(粒径5 mm的塑料)污染问题日益严重.以鄱阳湖湿地候鸟栖息地之一的白沙湖为研究区,采集了湖岸边、湖中心和候鸟活动区域的湖水、底泥和候鸟粪便,利用浮选分离法对其中的微塑料进行分离,分析其微塑料污染特征.结果表明:(1)研究区不同采样点水体和底泥中微塑料丰度有较大差异,表现为湖中心湖岸边候鸟活动区域,水体和底泥中微塑料平均丰度分别为263.28个·m~(-3)和215.9个·kg~(-1),候鸟粪便中微塑料平均丰度为4.93个·g~(-1).研究区存在颗粒、薄膜、碎片和纤维这4种不同形貌的微塑料.(2)水体中微塑料以颗粒类最多,颜色主要为红色,微塑料粒径丰度表现为1 mm1～2 mm2～3 mm3～5 mm,且基本呈随粒径增大丰度减小的趋势.(3)底泥中微塑料以纤维类为主,颜色主要为紫色,湖岸边和鸟类栖息地微塑料粒径以1 mm为主,湖中心以1～2 mm为主.(4)候鸟粪便内微塑料以颗粒类为主,颜色主要为红色,粒径以1 mm为主.(5)水体、底泥和候鸟粪便中微塑料类型分布无一致性,水体和候鸟粪便颜色和粒径分布保持一致.可见,鄱阳湖鸟类栖息地已经受到了微塑料的污染,鸟类也无可避免地接触到了微塑料,警示人们微塑料将会是候鸟的新兴威胁.     

Interspecific Patterns of Genetic Diversity in Birds: Correlations with Extinction Risk

Abstract:  Birds are frequently used as indicators of ecosystem health and are the most comprehensively studied class in the animal kingdom. Nevertheless, a comprehensive, interspecific assessment of the correlates of avian genetic diversity is lacking, even though indices of genetic diversity are of considerable interest in the conservation of threatened species. We used published data on variation at microsatellite loci from 194 bird species to examine correlates of diversity, particularly with respect to conservation status and population size. We found a significant decline in mean heterozygosity with increasing extinction risk, and showed, by excluding species whose heterozygosity values were calculated with heterospecific primers, that this relationship was not dependent on ascertainment bias. Results of subsequent regression analyses suggested that smaller population sizes of threatened species were largely responsible for this relationship. Thus, bird species at risk of extinction are relatively depauperate in terms of neutral genetic diversity, which is expected to make population recovery more difficult if it reflects adaptive genetic variation. Conservation policy will need to minimize further loss of diversity if the chances of saving threatened species are to be maximized.     

应用GPRS技术的环境状况远程实时自动监测系统

GPRS（General Packet Radio Service）无线通信网络具有永远在线、快速登录、高速传输、分组交换、费用低廉的优势。针对当前城乡饮用水源和废水污染严重,企业排出废气大幅度超标。区域环境噪声、交通噪声升级等日益严峻的环境现状,提出了“应用GPRS移动通信新技术,实现昼夜不问断、无盲点的远程实时环境自动监测系统”方案,大幅度提升“环境监测、环境治理”的科技水平。