USING TREND INDICES FOR ENDANGERED SPECIES

Initial appraisals of the status of endangered large-mammal populations may have to depend on indices of population trend. Such indices may possibly be improved by using auxiliary variables. Various models were studied for populations of the Florida manatee (Trichechus manatus latirostris), Yellowstone grizzly bear (Ursus arctos horribilis), and Hawaiian monk seal (Monachus schauinslandi). Several criteria for checking validity of the fitted models were considered, and the simple R² criterion appears to provide useful comparisons. Multiple regression models overestimated the rate of change of the East Coast manatee population as determined from three other sources (a covariance model, a non-linear model, and the rate estimated from reproductive and survival data). A multiple regression model for grizzly bears using three auxiliary variables exhibited a fairly high R² (0.84) and appeared to provide a better fit than did a non-linear model. A beach count index for Hawaiian monk seals seemed to be unreliable for year-to-year comparisons in contrast to total population counts and estimates from a capture-recapture method. The use of auxiliary variables for checking and improving trend index data appears feasible and well worthwhile.     

Additional Circular Systematic Sampling Methods

Several systematic sampling methods have been used to estimate the population mean when size of the population is a multiple of sample size. Among these, only few methods have been extended and used to estimate mean of the population when its size is not a multiple of sample size. In this paper, new methods called balanced circular systematic sampling and centered circular systematic sampling are introduced by extending balanced systematic sampling method and centered systematic sampling method respectively. These methods are compared with circular systematic sampling using average variance of corrected sample means for populations exhibiting approximate linear and parabolic trends. The suggested methods are found suitable to estimate the population mean.     

Markov Systematic Sampling

In this paper, a new systematic sampling scheme with Markovian behaviour which yields positive first order inclusion probabilities for all units and positive second order inclusion probabilities for all pairs of units is introduced. The suggested method has been compared with sample random sampling, stratified random sampling, linear systematic sampling and systematic sampling with two random starts for the populations exhibiting exponential trend, autocorrelatedness and randomness. Throughout the discussion, the sample size is assumed to be even and the population size is a multiple of the sample size. The suggested method works well for estimating a finite population total for the population exhibiting exponential trend.     

中国碳交易市场的特征、动力机制与趋势——基于国际经验比较

建立和完善碳交易市场是目前各国政府控制温室气体排放、积极应对全球气候变化的重要途径之一,厘清其发展特征和动力是推动碳交易的前提。将碳交易市场作为自然-经济-社会复合生态系统反馈机制的一环,从国际、国内两个尺度对碳交易市场的特征、动力机制和趋势做了分析,发现国际气候谈判的核心利益、减排的融资需求、货币霸权是碳交易市场全球化和金融化的主要驱动力。中国碳交易市场发展具有分阶段、市场规模大、发展不平衡、试点区域构建了碳交易政策体系等特征。鉴于中国经济增速快、碳排放增量大、能源依赖性大、区域发展不平衡、政府主导经济发展和外围保障体系不够完善等因素影响下,国内减排压力和国际声誉作为内在驱动机制,与国际相通的驱动机制共同促使形成具有中国特色的全国统一碳交易市场。同时,中国碳交易市场存在规模和业务扩大、制度更加完善、成为有世界话语权的碳交易市场等发展趋势。     

中国西北干旱区蒸散发时空动态特征

利用MODIS ET数据集中2000—2014年的地表实际蒸散发量产品,运用变异系数、Theil-Sen median趋势分析与MannKendall检验和Hurst指数法,研究了中国西北干旱区蒸散发的空间格局、不同维度的空间异质性和时间变化特征及未来趋势预测。结果表明:(1)2000—2014年全区蒸散发量总体较小,蒸散发量小于200 mm的区域占总面积的38.329%。在空间上ET自山区向两侧平原减少,不同土地覆盖的ET大小为:林地农用地草地稀疏植被。受降水和土地覆盖的综合影响,ET的高值区(400 mm)主要在降水丰富的山区林地和草地,而低值区(200 mm)主要在降水较少的平原稀疏植被区和草地。(2)近15年全区蒸散发变异程度不明显,以相对较低的波动变化为主。各亚区内波动较低区域的比例为:北疆天山祁连山内蒙西部河西走廊南疆。(3)15年间全区年均蒸散发量呈波动变化,总体有微弱的减小趋势,变化率为-0.9348 mm/a。基于像元尺度的分析也表明全区ET以减小的变化趋势为主,但各亚区的减小程度各异:天山内蒙西部河西走廊北疆祁连山,仅南疆有增加趋势。(4)全区ET的Hurst指数均值为0.689,Hurst指数大于0.5的范围所占比例为80.033%,未来全区蒸散发的变化趋势以持续性减小为主。其中22.003%区域的变化趋势无法确定。未来各亚区ET的减少趋势为:内蒙西部天山河西走廊北疆祁连山南疆。     

OBSERVER VARIABILITY IN PINNIPED COUNTS: GROUND-BASED ENUMERATION OF WALRUSES AT HAUL-OUT SITES

Pinnipeds are often monitored by counting individuals at haul-out sites, but the often large numbers of densely packed individuals at these sites are difficult to enumerate accurately. Errors in enumeration can induce bias and reduce precision in estimates of population size and trend. We used data from paired observers monitoring walrus haul-outs in Bristol Bay, Alaska, to quantify observer variability and assess its relative importance. The probability of a pair of observers making identical counts was < 0.1 for walrus groups with >50 individuals. Mean count differences ranged up to 25% for the largest counts, depending on beach and observers. In at least some cases, there was a clear tendency for counts of one observer to be consistently greater than counts of the other observer in a pair, indicating that counts of at least one of the observers were biased. These results suggest that efforts to improve accuracy of counts will be worthwhile. However, we also found that variation among observers was relatively small compared to variation among visits to a beach so that efforts to account for other sources of variation will be more important.     

Recent trends in Lake Ladoga ice cover

This contribution reviews diversity of turbellarian species by biogeographical regions, with comments on species biology. The review draws on the database available at http://www.devbio.umesci.maine.edu/styler/turbellaria. Comparisons between regions suggest that species richness may be at least one order of magnitude higher than the currently reported number of species. In the context of the recent reconstructions of phylogeny of Platyhelminthes based on molecular data, the paper allows inferences as to the history of colonization of freshwaters by turbellarians. Specifically, four, or perhaps six, major invasions of freshwater habitats may have occurred in the Pangean period, each of which gave rise to a monophyletic freshwater taxon. In addition, several occasional invasions by representatives of marine taxa must have taken place.     

恢复生态学焦点问题

就恢复生态学的概念、近期的发展趋势与前沿命题、传统生态学理论在生态恢复过程中的应用及恢复生态学的社会性等核心问题展开论述。恢复生态学是一门年轻的学科,迄今尚无统一的定义。代表性的有3方面的学术观点。第1种强调受损的生态系统要恢复到理想的状态;第2种强调其应用生态学过程;第3种强调生态整合性恢复。笔者认为,恢复生态学是研究生态系统退化的原因、退化生态系统恢复与重建的技术与方法、过程与机理的科学。从近年的国际恢复生态学大会来看,恢复生态学研究近期主要有3个方面的发展趋势。一是强调自然恢复与社会、人文的耦合。认为恢复生态是全球性的,不只是自然的过程,应有全社会的支持,包括政治、经济和人文的介入。二是强调无论是在地域上还是在理论上都要跨越边界。有效的生态恢复实践在地域上要求多地区甚至是多国家的合作,在理论上要求多学科的交叉与耦合。三是强调以生态系统为基点,在景观尺度表达。随着环境和经济问题的全球化,生态系统和景观尺度的恢复生态学研究引起了越来越多的关注。2004年第15届国际恢复生态学大会的会议主题已定为：恢复、景观与设计。在当前研究趋势的基础上,提出了恢复生态学当前研究的6个前沿命题：恢复生态学的学科理论框架研究、恢复生态系统的功益研究、生物多样性在生态恢复中的作用研究、生态恢复对全球变化的响应研究、生态恢复立法研究和生态恢复与社会、经济的整合性研究。退化生态系统的恢复与重建是一项十分复杂的系统工程,尤其需要生态学理论的指导。多数生态学理论已被应用于恢复生态学的研究与实践。结合实例,着重阐述了生态系统演替理论在生态恢复中的应用。恢复生态与全球变化间的相互作用研究越来越多的引起了人们的关注,但多数研究仍停滞在定性研究阶段。在广东的恢复生态学研究表明,广东省从1986年至1998年,植被覆盖从26％到51％,新造林绿化的植被每年可吸收、固定广东省年排放CO2量的一半。人类社会与自然环境的协调可持续发展,不仅要求实现生态环境的可持续,同时亦要求实现人类社会与经济的可持续发展。这就要求生态系统的恢复与重建必须同时实现生态、经济与社会效率的三重优化。中国科学院华南植物研究所生态中心在中国热带、南亚热带进行的退化生态系统的恢复与重建研究历时30余年,所产生的显著的经济和社会效益,在各个实验站点均已有所反映。     

太原市土壤中汞污染及成因研究

由于在城市的生产和生活等活动中长期排放含Hg的废弃物,致使城市土壤中的Hg含量越来越多,城市土壤的Hg污染越来越重,它所产生的危害已经引起人们的关注。本文通过对太原市不同地点的土壤中Hg含量进行监测,阐明了太原市土壤中Hg元素的含量、分布特征及其形成的原因,从而为太原市土壤Hg污染防治提供参考依据。     

植物群落物种共存机制:负密度制约假说

负密度制约假说主要描述由于资源竞争、有害生物侵害(比如病原微生物、食草动物捕食)等, 同种个体之间发生的相互损害行为; 它主要强调同种个体之间的相互作用, 解释自然群落物种共存的机理; 负密度制约机制主要在小尺度上降低群落内同种个体生长率, 同时提高个体死亡率, 从而为其他物种的生存提供空间和资源, 促进物种共存。目前负密度制约假说的检验研究主要侧重密度制约、距离制约、群落补偿效应等三个方面。最近, 研究者又探讨了近缘物种之间由于对相似资源的竞争所产生的负效应, 扩展了负密度制约假说, 进而提出异群保护假说和谱系多样性制约假说。负密度制约假说引起生态学家长久的探讨和关注, 世界范围内大尺度森林动态样地的建立, 又为探索不同尺度上密度制约效应的研究提供了条件。然而目前的研究仍然存在不足, 比如负密度制约假说的检验受到其他因素的干扰、区域研究不平衡等。因此, 生态学家们仍然怀疑负密度制约效应调节群落物种共存的重要性, 但是目前的研究还没有发现否定负密度制约假说的充分证据。