瑞典区域气候模拟计划(SWECLIM)综述

瑞典区域气候模拟计划(SWECLIM)是一个历时6年半的国家研究网络计划,该研究网络主要涉及区域气候模拟、区域气候变化预测以及水文影响评估,并且为广大的利益相关人士提供相应信息.大部分研究活动主要针对北欧区域气候系统.最终促使建立一个先进的大气-海洋-水文相耦合的区域气候模型系统和一套区域气候变化预测体系,并促成了相关数据的积累和相关过程研究的进步.反过来,作为对不同社会部门影响分析的一个起点,这些也可以用来作为信息源和为教育服务,而且还为国际气候研究做出了贡献.     

恢复力与可持续发展:在瞬息万变的世界中增强适应能力

由于在以往的自然资源政策上逐渐暴露出了两个带根本性的错误,人们开始意识到在环境管理理论和实践方面需要进行一场全球性的重大改革.第一个错误是毫无保留地假定生态系统对人类利用所作出的反应是呈线性关系、是可以预测和控制的.第二个错误是认定人类社会与天然系统可以分别对待,不必联系在一起进行考虑.然而,从世界各地收集到的证据表明,天然系统和人类社会系统是以非线性方式运行的、在其动态运行过程中均有其显著的极限,而且,人类社会与生态系统表现为一种紧密相联的、复杂的且不断演变的综合系统.本文是代表瑞典政府环境咨询委员会编写的一份报告的摘要,这份报告是作为向2002年8月26日～9月4日在南非约翰内斯堡召开的可持续发展世界首脑会议献礼的论文而撰写的.从概念上说,恢复力是一种能缓冲变化所带来的影响、学习知识和求得发展的能力,我们将它作为在一个纷纭复杂、快速变化的世界中,是否真正懂得如何维护和提高适应能力的一种参照标准来使用.在社会、生态综合系统中,有两种有用的工具可用来提高恢复力,一种是结构严谨的工作方案,另一种是积极的适应力管理.这两种工具都需要而且有助于形成这样一种社会环境:具有灵活开放的组织机构和多层次的监管体制,允许学习适应力方面的知识和提高适应力但又不妨碍对未来的发展作出选择.     

Temporal changes in Ohio amniocentesis utilization during the first twelve years (1972–1983), and frequency of chromosome abnormalities observed

The history of amniocentesis utilization in the seventh largest state of the United States is documented from its inception in 1972 through the first half of 1984. Amniocentesis utilization ratios for Ohio residents aged ⩾35 have increased from 0.21 per cent (19/9091) in 1972 to 23.4 per cent (1655/7531) in 1983, representing an average annual growth rate of 43.1 per cent. Of the amniocenteses performed from January 1, 1978–July 1, 1984, 71 per cent were referred for advanced maternal age (⩾35), 15 per cent for maternal anxiety (30–34), 10 per cent for family history or previous child with a genetic defect, and 4 per cent for other reasons. Between 1978-1983 utilization by women 45 years of age was only 20 per cent higher than women 35 even though their risk of giving birth to a Down syndrome child was about one order of magnitude higher. In addition, various factors were tested as to whether they affected utilization of amniocentesis by women ⩾35 during 1978 1983. A strong correlation of +0.89 existed between county population size and utilization ratios. No difference in utilization was found between whites and nonwhites, regardless of county population size. When utilization ratios were compared separately between Protestants, Catholics and other religions in Ohio's most populated county, no statistical differences were found. From 1978–July 1, 1984, the frequency of all cytogenetically abnormal chromosome results observed in Ohio amniocenteses to women ⩾35 was 2.48 per cent (187/7536). Of these, 2.15 per cent (162/7536) had unbalanced karyotypes. Future maximum amniocentesis utilization for women ⩾35 is estimated at 60–70 per cent.     

A novel role of computers in the natural products field

We describe several computer programs developed in our laboratory as aids in the determination of unknown molecular structures. These programs include CONGEN [1], for determination of all plausible structural candidates; REACT [2, 3], for simulation of sequences of chemical reactions; and STRUCC, for evaluating candidates and planning new experiments. We stress the importance of symbiosis between chemist and computer, the combination building on their respective strengths to increase the speed and accuracy of structural assignments.     

应对不确定性:呼吁建立新的科学政策论坛

科学界和政策界具有不同的目标,这就自然导致了对构成某种变化或现象的"检验"标准的差异,以及用不同的方法去描述不确定性和风险的持性及传达不确定性和风险.这些差异可能损害科学家、决策者和公众之间的有效沟通,同时也限制了科学家所愿意研究的社会紧迫问题的类型.本文主要回顾了一系列处理不确定性问题的方法,阐述了当科学和政策不能很好协调时所可能引起的一些错误.并在此基础上,特别针对解决不确定性问题提出了一些具体建议,包括重构科学规范,建立由科学、政策两方面领导广泛参加的科学政策论坛.     

Cover of Perennial Grasses in Southeastern Arizona in Relation to Livestock Grazing

Tolerance of particular grasslands to the activities of domestic livestock may depend on their historic association with native grazing animals. Southwestern grama ( Bouteloua ) grasslands are floristically allied to the North American Central Plains but lie outside the historic range of the plains' principal ungulate grazer, alics bishop . We compared perennial grassland cover and species composition on eight sites transacted by the boundary fence of a 3160-ha, 22-year-old livestock exclosure in a grama grassland in southeastern Arizona. Total grass canopy cover was greatest on the ungrazed portion of each of the eight sites. Two short stoloniferous species ( Hilaria belangeri and Bouteloua eriopoda ) were the only taxa substantially more abundant on grazed quadrats overall. Among these and eight taller budgerigars, there was a strong positive correlation between potential height and response to release from grazing, with the three tallest species showing the greatest increases on ungraded treatments ( emization curtailment, Boilermaker barbarians , and emizations intermixed ). emization gracious , the most abundant grass in the region, showed an intermediate response to livestock exclusion, Gram grasslands at the Arizona site have changed more and in different ways following livestock exclusion than those on the Central Plains of Colorado. Contributing factors may include: (1) greater annual precipitation at the Arizona site, (2) the much larger size of the Arizona livestock exclosure, and (3) the absence of extensive grazing by native ungulates in the Southwest since the Pleistocene. Livestock grazing appears to be an exotic ecological force in these southwestern grasslands, and one destructive of certain components of the native flora and fauna.     

Crypsis versus intimidation—anti-predation defence in three closely related butterflies

Butterflies that hibernate exhibit particularly efficient defence against predation. A first line of defence is crypsis, and most hibernating butterflies are leaf mimics. When discovered, some species have a second line of defence; the peacock, I. io, when attacked by a predator flicks its wings open exposing large eyespots and performs an intimidating threat display. Here we test the hypothesis that butterflies relying solely on leaf mimicking and butterflies with an intimidating wing pattern, when attacked, exhibit different behavioural suites—because leaf mimicking is best implemented by immobility, whereas intimidating coloration is best implemented by intimidating behaviour. In laboratory experiments blue tits, Parus caeruleus, were allowed 40 min to attack single individuals of three species of butterfly: one relying solely on crypsis, the comma, Polygonia c-album; one relying on intimidating wing pattern in addition to crypsis, the peacock; and one intermediate species, the small tortoiseshell Aglais urticae. The results are in accordance with expectations and demonstrate that: (1) birds take longer to discover the leaf mimicking species, the comma, than the tortoiseshell and the peacock; (2) the comma remained motionless throughout experimental trials but small tortoiseshells and peacocks flicked their wings when attacked; (3) the most intimidating butterfly, the peacock, started flicking its wings at a greater distance from the attacking bird than the small tortoiseshell; and (4) the intimidating pattern and behaviour of peacocks was effective—when discovered, all peacocks survived interactions with blue tits, whereas only 22% of commas and 8% of small tortoiseshells survived.     

Do plant density, nutrient availability, and herbivore grazing interact to affect phlorotannin plasticity in the brown seaweed Ascophyllum nodosum

Plants have different strategies to cope with herbivory, including induction of chemical defences and compensatory growth. The most favourable strategy for an individual plant may depend on the density at which the plants are growing and on the availability of nutrients, but this has not been tested previously for marine plant–herbivore interactions. We investigated the separate and interactive effects of plant density, nutrient availability, and herbivore grazing on the phlorotannin (polyphenolic) production in the brown seaweed Ascophyllum nodosum. Seaweed plants grown at low or high densities were exposed either to nutrient enrichment, herbivorous littorinid gastropods (Littorina obtusata), or a combination of nutrients and herbivores in an outdoor mesocosm experiment for 2 weeks. Seaweeds grown at a low density tended to have higher tissue nitrogen content compared to plants grown at a high density when exposed to elevated nutrient levels, indicating that there was a density dependent competition for nitrogen. Herbivore grazing induced a higher phlorotannin content in plants grown under ambient, but not enriched, nutrient levels, indicting either that phlorotannin plasticity is more costly when nutrients are abundant or that plants responded to herbivory by compensatory growth. However, there were no significant interactive or main effects of plant density on the seaweed phlorotannin content. The results indicate that plants in both high and low densities induce chemical defence, and that eutrophication may have indirect effects on marine plant–herbivore interactions through alterations of plant chemical defence allocation.     

Nitrogen spatial heterogeneity influences diversity following restoration in a ponderosa pine forest, Montana.

The resource heterogeneity hypothesis (RHH) is frequently cited in the ecological literature as an important mechanism for maintaining species diversity. The RHH has rarely been evaluated in the context of restoration ecology in which a commonly cited goal is to restore diversity. In this study we focused on the spatial heterogeneity of total inorganic nitrogen (TIN) following restoration treatments in a ponderosa pine (Pinus ponderosa)/Douglas-fir (Pseudotsuga menziesii) forest in western Montana, USA. Our objective was to evaluate relationships between understory species richness and TIN heterogeneity following mechanical thinning (thin-only), prescribed burning (burn-only), and mechanical thinning with prescribed burning (thin/burn) to discern the ecological and management implications of these restoration approaches. We employed a randomized block design, with three 9-ha replicates of each treatment and an untreated control. Within each treatment, we randomly established a 20 x 50 m (1000 m2) plot in which we measured species richness across the entire plot and in 12 1-m(2) quadrats randomly placed within each larger plot. Additionally, we measured TIN from a grid consisting of 112 soil samples (0-5 cm) in each plot and computed standard deviations as a measure of heterogeneity. We found a correlation between the net increase in species richness and the TIN standard deviations one and two years following restoration treatments, supporting RHH. Using nonmetric multidimensional scaling ordination and chi-squared analysis, we found that high and low TIN quadrats contained different understory communities in 2003 and 2004, further supporting RHH. A comparison of restoration treatments demonstrated that thin/burn and burn-only treatments created higher N heterogeneity relative to the control. We also found that within prescribed burn treatments, TIN heterogeneity was positively correlated with fine-fuel consumption, a variable reflecting burn severity. These findings may lead to more informed restoration decisions that consider treatment effects on understory diversity in ponderosa pine/Douglas-fir ecosystems.