阳离子型聚丙烯酰胺投加量对絮体性状特征的影响

应用激光粒度仪、影像分析及沉降分析技术研究了阳离子型聚丙烯酰胺(PAM)对混凝过程絮体的粒度、强度及分形维数等微观特性及絮体沉降速率的影响.结果表明,絮体的粒度、强度及分形维数等微观特性与阳离子型PAM的投加量有关,存在一个PAM的最佳投加剂量.在此最佳投加剂量下,系统内絮体的粒度与强度最大、分形维数最小、絮体沉降速率最大.     

福建梅花山国家级自然保护区拟赤杨种群分布格局的分形分析

分形理论中的计盒维数、信息维数和关联维数能分别从空间占据程度、格局强度和个体空间关联的尺度变化角度,揭示种群分布格局的尺度变化特征.本文应用以上3个分形维数探讨了福建梅花山国家级自然保护区拟赤杨种群分布格局的多尺度分布规律,计算结果表明,拟赤杨种群的分布格局具有分形特征,其计盒维数为1.0298～1.2982,信息维数为0.9728～1.2464,关联维数为0.5089～0.8047.拟赤杨种群的计盒维数、信息维数较高,而关联维数较小,表明该种群的分布格局强度相对较高,结构相对复杂,具有集聚分布的趋势.     

飞灰残炭分形特征对汞吸附反应的影响

在残炭汞吸附模拟试验的基础上,采用分形理论,研究了飞灰残炭物理结构的分形特征及其对残炭汞吸附反应的影响,残炭的比表面积与残炭及其炉前煤的分形维数大致呈正相关关系．汞的吸附量不仅同其比表面积相关,而且与分形维数有关．     

絮凝体的DLA分形模拟及其分形维数的计算方法

运用有限扩散凝聚(DLA)模型对絮凝体的成长过程进行了二维模拟.模拟絮凝体分别采用密度函数法、回转半径法、图像分析法进行分形维数计算,分形维数均随模拟絮凝体尺寸的增大而减小.三种计算方法的结果显示,密度函数法和回转半径法得到的分形维数基本相当,但图像分析法所得到的分形维数较小,约为密度函数法和回转半径法所得到的分形维数的0.8左右,其原因可能是图像分析过程中计算机对图像的识别误差所致.以DLA模型模拟得到的絮凝体内部的孔隙率随絮凝体尺寸的增大而增加.絮凝体中孔隙率的增加是絮凝体密度减小、结构松散的主要原因,也是絮凝体分形维数降低的主要因素.     

分形理论及其在混凝研究中的应用

随着人们对分形理论研究的深入,其在混凝研究中的应用日趋广泛.分形理论的出现使人们更清楚地认识了混凝过程中出现的复杂现象及无规则形态,从而为今后对混凝过程的进一步研究提供了有力工具.该文不仅对分形理论的基本知识进行了简单地介绍,并且还对其在絮体形态学和混凝动力学方面的研究应用进行了阐述,同时列举了分形维数在混凝工艺中的具体应用实例,最后提出了目前存在的问题及自己的见解.图1,参21.     

基于多元线性模型、支持向量机(SVM)模型和地统计方法的地表水溶解性总固体(TDS)估算及其精度对比——以艾比湖流域为例

地表水溶解性总固体(TDS)是地表水各组分浓度的总指标,是地表水水化学特性长期演变的最终结果,也是表征水文地球化学作用过程的重要参数,TDS的高低直接影响地表水的含盐量.本研究以艾比湖流域为研究对象,结合实测地表水TDS数据;选用准同步的Landsat OLI数据,首先,利用光谱诊断指数选取与地表水TDS相关性较高的波段,其次,利用地统计方法、多元线性回归模型和支持向量机(SVM)模型对TDS进行预测,并对其结果进行精度比较.结果表明,SVM模型为最优估测模型,拟合决定系数R2为0.97,均方误差(RMSE)为50.59;多元线性回归模型的精度与SVM模型精度较为接近,拟合决定系数R2为0.9,RMSE为66.55;地统计克里格插值法预测精度最低,拟合决定系数R2为0.87,RMSE为95.73.遥感估测SVM模型预测值在大区域能较好地反映出艾比湖流域TDS的总体特征.该模型在水质遥感领域的应用中具有良好的可行性和有效性,其预测结果也与艾比湖流域水体TDS的实际分布相吻合,因此遥感估测SVM模型在水质估测中具有一定的应用潜力.     

基于高光谱技术的土壤镉污染分级评价研究

提出一种利用高光谱技术进行土壤镉污染分级评价的方法。以FieldSpec 3地物光谱仪采集厂矿区土壤光谱反射率175份,随机分成校正集（135份）和检验集（40份）。光谱经小波去噪和标准归一化（SNV）处理后,以主成分分析法（PCA）降维。将降维所得的前5个主成分数据为输入变量,分别采用Fisher线性判别、Byes逐步判别、模糊模式识别、BP-ANN判别以及SVM 5种方法建立了土壤镉污染分级评价模型,并利用40个未知样对模型进行检验。结果表明：Fisher线性判别准确率为77.5%,Byes逐步判别与模糊模式识别预测为80.0%,BP-ANN模型预测精度为82.5%,SVM模型预测精度最高,达85.0%。说明采用高光谱技术进行土壤镉污染分级评价是可行,其中SVM是建模的优选算法。     

神经网络模型在黄河水质预报中的应用分析

为提高黄河水质预测的精度和实用性,引入神经网络技术建立黄河水质预测模型,采用LM(Levenberg-Marquardt)算法提高预测精度,并将模型应用于黄河小花段(小浪底-花园口段)的水质预测.预测结果表明,在建立黄河入河污染物和功能区水质的输入响应关系模型的实际应用中,神经网络模型和LM算法可以取得较好的预测效果.     

干热河谷植物沙丘形态及植物功能性状特征与土壤分形维数的关系北大核心CSCD

为了解植物沙丘形态及植物功能性状特征对坡面泥沙拦截的作用机制,以干热河谷典型区蒋家沟流域为研究区,采用典型样地调查、野外实地观测和室内试验处理的方法,测定失稳性坡面42个植物沙丘(包括扭黄茅20株、拟金茅13株、丛毛羊胡子草9株)的形态特征、植物功能性状特征和沙丘土壤的颗粒组成,并运用分形理论计算分形维数,分析分形维数与植物沙丘形态特征及功能性状特征间的相关关系.结果表明:(1)3种植物沙丘的形态特征及植物的功能性状特征均无显著差异性.(2)3种植物沙丘间、沙丘与上方30 cm处的土壤各粒径百分比含量和分形维数均无显著差异.(3)干热河谷植物沙丘土壤颗粒的分形维数(D)与植物含水率、根系深度呈极显著正相关性(P <0.01),与沙丘长度显著正相关(P <0.05),与植物其他形态、功能性状特征和沙丘其他形态特征间均无显著相关性.上述研究表明不同植物沙丘各类特征间均无显著差异;沙丘未改变坡面原有土壤颗粒的分布特征;沙丘土壤分形维数可表征植物含水率、根系深度及沙丘长度的大小.结果有助于加深植物控制土壤侵蚀效应的认识,可为干热河谷水土流失治理提供科学依据.(图5表1参35)     

洪涝灾害干扰下受损自然恢复林地土壤基本性状及分形维数特征

选取重大洪涝灾害干扰下受损自然恢复3种不同林地(毛竹林、杉木林、次生阔叶林)为研究对象,以未受损林地为对照,测定不同林型土壤基本性状指标(包括土壤颗粒组成在内的物理性质、主要养分含量),并运用分形理论计算了分形维数D值,探讨分形维数与土壤基本性状的相关关系.结果表明:(1)3种不同林型土壤均以粉粒含量占比最大,分形维数在2.58-2.70之间,0-10 cm土层分形维数表现为毛竹林杉木林次生阔叶林,受损自然恢复林地未受损林地,其中次生阔叶林的受损自然恢复林地与未受损林地差异显著.(2)毛竹林与次生阔叶林土壤容重表现为受损自然恢复林地显著大于未受损林地,土壤含水量、毛管持水量、非毛管孔隙度与总孔隙度则相反,受损自然恢复与未受损杉木林间土壤物理性质的差异较小;各林型土壤养分含量随土层深度的增加而降低,且受损自然恢复林地显著低于未受损林地,总体恢复状况表现为杉木林次生阔叶林毛竹林.(3)土壤分形维数与土壤黏粒含量、土壤容重存在显著正相关关系,与有机质、全氮、土壤含水量、毛管持水量、非毛管孔隙度及总毛管孔隙度存在显著负相关关系.因此,分形维数能够客观地表征土壤的结构特征以及土壤养分肥力特征;受损恢复林地土壤条件还未达到未受损林地的水平,对恢复状况较差的毛竹林,可以适当地进行人工植树造林,优化群落结构,进而改善土壤条件,促进灾害干扰下受损植被的恢复进程.     

Achieving Open Access to Conservation Science

Conservation science is a crisis discipline in which the results of scientific enquiry must be made available quickly to those implementing management. We assessed the extent to which scientific research published since the year 2000 in 20 conservation science journals is publicly available. Of the 19,207 papers published, 1,667 (8.68%) are freely downloadable from an official repository. Moreover, only 938 papers (4.88%) meet the standard definition of open access in which material can be freely reused providing attribution to the authors is given. This compares poorly with a comparable set of 20 evolutionary biology journals, where 31.93% of papers are freely downloadable and 7.49% are open access. Seventeen of the 20 conservation journals offer an open access option, but fewer than 5% of the papers are available through open access. The cost of accessing the full body of conservation science runs into tens of thousands of dollars per year for institutional subscribers, and many conservation practitioners cannot access pay‐per‐view science through their workplace. However, important initiatives such as Research4Life are making science available to organizations in developing countries. We urge authors of conservation science to pay for open access on a per‐article basis or to choose publication in open access journals, taking care to ensure the license allows reuse for any purpose providing attribution is given. Currently, it would cost $51 million to make all conservation science published since 2000 freely available by paying the open access fees currently levied to authors. Publishers of conservation journals might consider more cost effective models for open access and conservation‐oriented organizations running journals could consider a broader range of options for open access to nonmembers such as sponsorship of open access via membership fees. Obtención de Acceso Abierto a la Ciencia de la Conservación     

Rapid,recurring, structured survey versus bioblitz for generating biodiversity data and analysis with a multispecies abundance model

A bioblitz inexpensively and quickly generates biodiversity data, but bioblitzes are often conducted with haphazard, unreplicated sampling. Results tend to be taxonomically, geographically, or temporally biased, lack metadata, and consist of lists of observed taxa that do not enable further analyses or correction for imperfect detection. A rapid, recurring, structured survey (RRSS) uses a structured sampling design and temporal and spatial replication to survey randomly selected sites on a conservation property. We participated in a loosely structured bioblitz and a subsequent RRSS at Big Canoe Creek Nature Preserve in Springville (St. Clair County), Alabama (USA) to compare observed richness derived from the 2 survey approaches. The RRSS data structure enabled us to fit models that accounted for imperfect detection to estimate abundances, occupancy probabilities, and habitat associations. The loosely structured bioblitz data could not be used in such models. We present a new integrated multispecies abundance model that we applied to avian RRSS data. Our model extension enables estimation for the community, employs data augmentation to estimate the number of undetected species, and incorporates covariates. The RRSS generated a more comprehensive and less biased list of observed taxonomic richness than the loosely structured bioblitz (e.g., 73 vs. 45 bird species and 104 vs. 63 insect families from the RRSS vs. loosely structured bioblitz, respectively). Models fit to the RRSS data identified seasonal patterns in avian community composition and allowed for estimation of habitat–occupancy relationships for insect taxa. The RRSS protocol has potential for broad transferability as a standardized, quick, and inexpensive way to inventory biodiversity and estimate ecological parameters while providing an outreach opportunity.     

Compliance with and ecosystem function of biodiversity offsets in North American and European freshwaters

Land-use change via human development is a major driver of biodiversity loss. To reduce these impacts, billions of dollars are spent on biodiversity offsets. However, studies evaluating offset project effectiveness that examine components such as the overall compliance and function of projects remain rare. We reviewed 577 offsetting projects in freshwater ecosystems that included the metrics project size, type of aquatic system (e.g., wetland and creek), offsetting measure (e.g., enhancement, restoration, and creation), and an assessment of the projects’ compliance and functional success. Project information was obtained from scientific and government databases and gray literature. Despite considerable investment in offsetting projects, crucial problems persisted. Although compliance and function were related to each other, a high level of compliance did not guarantee a high degree of function. However, large projects relative to area had better function than small projects. Function improved when projects targeted productivity or specific ecosystem features and when multiple complementary management targets were in place. Restorative measures were more likely to achieve targets than creating entirely new ecosystems. Altogether the relationships we found highlight specific ecological processes that may help improve offsetting outcomes.     

Some polyphagous Homoptera gain protection from their natural enemies by feeding on the toxic plantsSpartium junceum andErythrina corallodendrum (Leguminosae)

Summary Interactions were studied among alkaloid-containing legumes (Erythrina corallodendrum andSpartium junceum) and non-toxic plants (Citrus sinensis, Cucurbita moschata andEuphorbia tirucalli), several polyphagous homopterans,Aphis craccivora (Aphididae),Icerya purchasi, I. aegyptiaca (Margarodidae),Lepidosaphes ulmi (Diaspididae) andPlanococcus citri (Pseudococcidae), and some major natural enemies of these homopterans. Significant reductions in survival due to negative effects of alkaloid containing as compared with non-alkaloidal plants were recorded for the predatorsRodolia cardinalis andChilocorus bipustulatus, but not forCryptolaemus montrouzieri (Coleoptera: Coccinellidae),Chrysoperla carnea (Neuroptera: Chrysopidae) andSympherobius sanctus (Neuroptera: Sympherobiidae). The development time of the larvae or pupae ofR. cardinalis, C. carnea andS. sanctus was longer on the toxic plants than on the non-toxic ones. The percentage of parasitism ofA. craccivora collected from the non-alkaloidal plantsVicia palaestina andMelilotus albus was much higher than that onS. junceum. The parasitoid complexes ofA. craccivora differed between both plant groups. The nutritive value of honeydew ofI. purchasi andA. craccivora, as expressed by the life span ofEncyrtus infelix (Hymenoptera: Encyrtidae) adults, was also investigated. Life spans were significantly longer when the wasps fed on honeydew produced on non-alkaloidal plants (C. sinensis andPittosporum tobira) than on alkaloid containing plants whenI. purchasi — but notA. craccivora — was the producer. It is suggested that the chemical defense ofE. corallodendrum andS. junceum is exploited by polyphagous phytophages to reduce predation. In nature, population growth and density of four of the investigated homopterans are conspicuously high when they developed on the alkaloid containing plant species, and very low on non-alkaloid plants. The efficiency of their natural enemies may be reduced by sequestration of alkaloids (or other toxic plant compounds) or their transfer into excreted honeydew. Therefore it is assumed that a generalist phytophagous homopteran may be protected from its natural enemies, although at different rates of efficiency, if it can safely sequester the host allelochemical when it develops on toxic species within its host range.     

A palaeo-hydrogeological model for arsenic contamination in southern and south-east Asia

An argument is presented in which areas of natural arsenic contamination of modern groundwaters throughout Asia have a common origin. Arsenic originally accumulated in oceanic ferro-manganoan sediments of the eastern Palaeo-Tethys. This was further concentrated through oceanic crustal extinction in what later became the south-east Chinese accreted mineralised terrain. Proto-Himalayan uplift of this area created the palaeo-drainage systems of the Ganges – Brahmaputra, Irrawaddy, Mekong, and Red Rivers, with consequent headwater erosion of arsenic-rich sediments. Their downstream deposition as immature and easily redistributed Neogene sandstones, silts, and iron-rich clays has created secondary and tertiary reservoirs of adsorbed and authigenic arsenic, from which the current arsenic-rich groundwaters have evolved. Considering river basins within the above palaeo-hydrogeological framework provides a basis for assessing the risk of arsenic in groundwater basins of south and south-eastern Asia.     

Sequestration of cucurbitacin analogs by New and Old World chrysomelid leaf beetles in the tribe Luperini

Summary Two South American polyphagous leaf beetles,Diabrotica speciosa andCerotoma arcuata, selectively accumulated the bitter tasting compound 23,24-dihydrocucurbitacin D in their body after ingesting root tissues of cucurbit plants. Similarly, three Asian Cucurbitaceae-feeding specialists in the genusAulacophora were found to sequester the same compound. Cucurbitacin analogs were shown to deter feeding by a bird predator, indicating an allomonal role for these compounds in cucurbitacin-associated chrysomelid leaf beetles both of New and Old Worlds. The strong affinity to cucurbitacins, selective sequestration of the analogs and consequent protection from predators suggested an ecological adaptation mechanism developed in common among these two geographically isolated subtribes in the Luperini.     

Effects of Controlled Fire and Livestock Grazing on Bird Communities in East African Savannas

Abstract: In East Africa fire and grazing by wild and domestic ungulates maintain savannas, and pastoralists historically set fires and herded livestock through the use of temporary corrals called bomas. In recent decades traditional pastoral practices have declined, and this may be affecting biodiversity. We investigated the effects of prescribed fires and bomas on savanna bird communities in East Africa during the first and second dry seasons of the year (respectively before and after the rains that mark the onset of breeding for most birds). We compared abundance, richness, and community composition on 9‐ha burned plots, recently abandoned bomas, and control plots in the undisturbed matrix habitat over a 3‐year period. Generally, recently burned areas and abandoned bomas attracted greater densities of birds and had different community assemblages than the surrounding matrix. The effects of disturbances were influenced by interactions between primary productivity, represented by the normalized difference vegetation index, and time. Bird densities were highest and a greater proportion of species was observed on burned plots in the months following the fires. Drought conditions equalized bird densities across treatments within 1 year, and individuals from a greater proportion of species were more commonly observed on abandoned bomas. Yearly fluctuations in abundance were less pronounced on bomas than on burns, which indicate that although fire may benefit birds in the short term, bomas may have a more‐lasting positive effect and provide resources during droughts. Several Palearctic migrants were attracted to burned plots regardless of rainfall, which indicates continued fire suppression may threaten their already‐declining populations. Most notably, the paucity of birds observed on the controls suggests that the current structure of the matrix developed as a result of fire suppression. Traditional pastoralism appears critical to the maintenance of avian diversity in these savannas.     

Cost‐effective conservation of an endangered frog under uncertainty

How should managers choose among conservation options when resources are scarce and there is uncertainty regarding the effectiveness of actions? Well‐developed tools exist for prioritizing areas for one‐time and binary actions (e.g., protect vs. not protect), but methods for prioritizing incremental or ongoing actions (such as habitat creation and maintenance) remain uncommon. We devised an approach that combines metapopulation viability and cost‐effectiveness analyses to select among alternative conservation actions while accounting for uncertainty. In our study, cost‐effectiveness is the ratio between the benefit of an action and its economic cost, where benefit is the change in metapopulation viability. We applied the approach to the case of the endangered growling grass frog (Litoria raniformis), which is threatened by urban development. We extended a Bayesian model to predict metapopulation viability under 9 urbanization and management scenarios and incorporated the full probability distribution of possible outcomes for each scenario into the cost‐effectiveness analysis. This allowed us to discern between cost‐effective alternatives that were robust to uncertainty and those with a relatively high risk of failure. We found a relatively high risk of extinction following urbanization if the only action was reservation of core habitat; habitat creation actions performed better than enhancement actions; and cost‐effectiveness ranking changed depending on the consideration of uncertainty. Our results suggest that creation and maintenance of wetlands dedicated to L. raniformis is the only cost‐effective action likely to result in a sufficiently low risk of extinction. To our knowledge we are the first study to use Bayesian metapopulation viability analysis to explicitly incorporate parametric and demographic uncertainty into a cost‐effective evaluation of conservation actions. The approach offers guidance to decision makers aiming to achieve cost‐effective conservation under uncertainty.     

Parasitic wasps orient to green leaf volatiles

Summary Undamaged plants emit low levels of green leaf volatiles (GLVs), while caterpillar-damaged and artificially damaged plants emit relatively higher levels of certain GLVs. Female braconid parasitoids,Microplitis croceipes, oriented to both damaged plants and to individual GLVs in no-choice tests in a wind tunnel, but seldom oriented to undamaged plants. Female ichneumonid parasitoids,Netelia heroica, also oriented to individual GLVs in a wind tunnel. Males of both wasp species failed to orient to the GLVs. These data show that leaf-feeding caterpillars can cause the release of GLVs, and that parasitic wasps can respond to these odors by flying upwind (chemoanemotactic response), which brings the wasps to their caterpillar hosts. This supports the hypothesis that plants communicate with members of the third trophic level,i.e., plants under herbivore attack emit chemical signals that guide natural enemies of herbivores to sites of plant damage. In this interaction, the GLVs serve as tritrophic plant-to-parasitoid synomones. That parasitoids from two different wasp families oriented to GLVs suggests that the response may be widespread among the Hymenoptera.Mention of a commercial or proprietary product does not constitute an endorsement by the U.S. Department of Agriculture     

What Every Conservation Biologist Should Know about Economic Theory

Abstract: The last century has seen the ascendance of a core economic model, which we will refer to as Walrasian economics. This model is driven by the psychological assumptions that humans act only in a self‐referential and narrowly rational way and that production can be described as a self‐contained circular flow between firms and households. These assumptions have critical implications for the way economics is used to inform conservation biology. Yet the Walrasian model is inconsistent with a large body of empirical evidence about actual human behavior, and it violates a number of basic physical laws. Research in behavioral science and neuroscience shows that humans are uniquely social animals and not self‐centered rational economic beings. Economic production is subject to physical laws including the laws of thermodynamics and mass balance. In addition, some contemporary economic theory, spurred by exciting new research in human behavior and a wealth of data about the negative global impact of the human economy on natural systems, is moving toward a world view that places consumption and production squarely in its behavioral and biophysical context. We argue that abandoning the straightjacket of the Walrasian core is essential to further progress in understanding the complex, coupled interactions between the human economy and the natural world. We call for a new framework for economic theory and policy that is consistent with observed human behavior, recognizes the complex and frequently irreversible interaction between human and natural systems, and directly confronts the cumulative negative effects of the human economy on the Earth's life support systems. Biophysical economics and ecological economics are two emerging economic frameworks in this movement.