Robert Chambers and Thomas Henry Huxley, Science Correspondents: The Popularization and Dissemination of Nineteenth Century Natural Science

Robert Chambers and Thomas Henry Huxley helped popularize science by writing for general interest publications when science was becoming increasingly professionalized. A non-professional, Chambers used his family-owned Chambers' Edinburgh Journal to report on scientific discoveries, giving his audience access to ideas that were only available to scientists who regularly attended professional meetings or read published transactions of such forums. He had no formal training in the sciences and little interest in advancing the professional status of scientists; his course of action was determined by his disability and interest in scientific phenomena. His skillful reporting enabled readers to learn how the ideas that flowed from scientific innovation affected their lives, and his series of article in the Journal presenting his rudimentary ideas on evolution, served as a prelude to his important popular work, Vestiges of the Natural History of Creation. Huxley, an example of the new professional class of scientists, defended science and evolution from attacks by religious spokesmen and other opponents of evolution, informing the British public about science through his lectures and articles in such publications as Nineteenth Century. He understood that by popularizing scientific information, he could effectively challenge the old Tory establishment -- with its orthodox religious and political views -- and promote the ideas of the new class of professional scientists. In attempting to transform British society, he frequently came in conflict with theologians and others on issues in which science and religion seemed to contradict each other but refused to discuss matters of science with non-professionals like Chambers, whose popular writing struck a more resonant chord with working class readers. This revised version was published online in July 2006 with corrections to the Cover Date.     

Long‐term responses of leaf litter decomposition to temperature,litter quality and litter mixing in plateau wetlands

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Levels of organization in biology: on the nature and nomenclature of ecology's fourth level

Viewing the universe as being composed of hierarchically arranged systems is widely accepted as a useful model of reality. In ecology, three levels of organization are generally recognized: organisms, populations, and communities (biocoenoses). For half a century increasing numbers of ecologists have concluded that recognition of a fourth level would facilitate increased understanding of ecological phenomena. Sometimes the word "ecosystem" is used for this level, but this is arguably inappropriate. Since 1986, I and others have argued that the term "landscape" would be a suitable term for a level of organization defined as an ecological system containing more than one community type. However, "landscape" and "landscape level" continue to be used extensively by ecologists in the popular sense of a large expanse of space. I therefore now propose that the term "ecoscape" be used instead for this fourth level of organization. A clearly defined fourth level for ecology would focus attention on the emergent properties of this level, and maintain the spatial and temporal scale-free nature inherent in this hierarchy of organizational levels for living entities.     

Seasonal patterns of carbohydrate translocation and synthesis of structural carbon components in <Emphasis Type="Italic">Typha angustifolia</Emphasis>

Quantitative studies of material budgets and resource allocation patterns of emergent plants are needed to fully understand nutrient and carbon cycling in wetlands. Whole-plant translocation patterns of nonstructural carbohydrates and synthesis of structural carbon were documented using two (shallow and deepwater) populations of Typha angustifolia in floodplain habitats of the Arakawa River, Japan. Monthly and bimonthly measurements of the concentrations of total carbon, non-structural carbohydrates, and water-soluble carbohydrates, as well as, estimates of standing stocks of aboveground (AG) and belowground (BG) biomass for both populations from 2002 to 2004 are described here. Annual patterns of carbon gain, rates of carbohydrate translocation between AG and BG organs, and rates of synthesis of structural carbon were estimated. Upward translocation supported all AG production for approximately 30 days. Afterward, the fraction of AG production supported by upward translocation decreased linearly with time, and completely diminished by Day 80 (counted from first day of growth; March 15). At Day 80, material translocation was directed downward and the percentage of downward translocation relative to AG net production increased until Day 170; there was a vigorous increase in downward translocation prior to senescence. In early summer (Day 80–110), more than half of the translocated materials were transformed into structural components, but by Day 125 only 30% was synthesized into total structural carbohydrates. Prior to senescence, there was a greater percentage of nonstructural carbohydrates in the rhizomes. Across the growing season (Day 60–153), the total amount of downward translocation was found to be proportional to AG production and the quantitative evaluation of the carbon budget shed further insight into the translocation process of this rhizomatous aquatic plants. In addition, insights on the differences between shallow and deepwater populations were gained. Especially, the deepwater population supported a higher fraction of vertical rhizomes compared to individuals sampled from the shallow water population. Handling editor: S. M. Thomaz.     

Emerging climate‐driven disturbance processes: widespread mortality associated with snow‐to‐rain transitions across 10° of latitude and half the range of a climate‐threatened conifer

Climate change is causing rapid changes to forest disturbance regimes worldwide. While the consequences of climate change for existing disturbance processes, like fires, are relatively well studied, emerging drivers of disturbance such as snow loss and subsequent mortality are much less documented. As the climate warms, a transition from winter snow to rain in high latitudes will cause significant changes in environmental conditions such as soil temperatures, historically buffered by snow cover. The Pacific coast of North America is an excellent test case, as mean winter temperatures are currently at the snow–rain threshold and have been warming for approximately 100 years post‐Little Ice Age. Increased mortality in a widespread tree species in the region has been linked to warmer winters and snow loss. Here, we present the first high‐resolution range map of this climate‐sensitive species, Callitropsis nootkatensis (yellow‐cedar), and document the magnitude and location of observed mortality across Canada and the United States. Snow cover loss related mortality spans approximately 10° latitude (half the native range of the species) and 7% of the overall species range and appears linked to this snow–rain transition across its range. Mortality is commonly >70% of basal area in affected areas, and more common where mean winter temperatures is at or above the snow–rain threshold (>0 °C mean winter temperature). Approximately 50% of areas with a currently suitable climate for the species (相似文献   

Litter Decomposition of Scirpus maritimus L. in a Mediterranean Coastal Marsh: Importance of the Meiofauna during the Initial Phases of Detached Leaves Decomposition

Growth, senescence and decomposition rates of Scirpus maritimus were studied in a Mediterranean brackish wetland. Plant tussocks were tagged in March, 2002 and were totally dead by September, 2002. Decomposition rates were determined over 360 days using litter bag technique and mass loss, nutrient dynamics, fungal biomass, meiofauna and macroorganisms were determined. Decomposition rate of detached S. maritimus litter was 0.00196 (k, day^–1) with a 54% of mass lost observed in 1 year. The pattern of mass loss was characterized by an initial phase of fast loss of organic matter with high density of meiofauna and a decrease of oxygen content, followed by two slower phases, with no significant losses from 50 to 180 days and with 21% of mass lost from 180 to 360 days. Nitrogen (N) and phosphorus (P) content of plant litter increased during decomposition process whereas atomic C:N and C:P ratios decreased, suggesting a nutrient immobilization on plant detritus. Fungal biomass measured as ergosterol content decreased after submersion of leaves, indicating that their importance in litter decomoposition decreases in submerged leaves during the first days of decomposition. An inverse relationship (r = –0.79, P < 0.005) was observed between ergosterol content and nematodes density on S. maritimus litter. Our results suggest that in Mediterranean brackish marshes, where large amounts of dead organic matter is accumulated over the sediment surface, decomposition process is greatly affected by extremely high temperatures in summer that, if water is available, accelerates microbial activity decreasing oxygen content thus slowing decomposition. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

挺水植物与浮叶植物光合荧光特性的差异

为探讨自然生境中不同生活型水生植物光合生理特征的差异,选取4种挺水植物菖蒲(Acorus calamus L.)、再力花(Thalia dealbata Fraser)、梭鱼草(Pontederia cordata L.)、茭草(Zizania latifolia(Griseb.)Stapf),以及4种浮叶植物黄睡莲(Nymphaea mexicana Zucc.)、莼菜(Brasenia schreberi J.F.Gmel.)、金银莲花(Nymphoides indica(L.)O.Kuntze)、菱(Trapa bispinosa Roxb.)为研究对象,比较其叶绿素荧光参数、色素组成和比叶重的差异。研究发现,高光强下挺水植物电子传递速率(ETR)、非光化学淬灭(NPQ)等光合荧光参数、以及低光强下ETR拟合曲线的初始斜率(α)均值显著大于浮叶植物。不同挺水植物间光系统Ⅱ(PSⅡ)最大光化学效率(F_v/F_m)、ETR、NPQ、最大潜在电子传递速率(Ps)、最大电子传递速率(ETR_m)及饱和光强(E_m)变化幅度较大;不同浮叶植物间上述参数变化幅度较小。挺水植物叶绿素(Chls)、类胡萝卜素(Cars)含量均值也高于浮叶植物。但由于比叶重(SLW)的影响,不同水生植物间单位叶面积和单位叶鲜重色素含量的变化规律略有不同。挺水植物中再力花、梭鱼草光合能力较强,其光合荧光参数和色素比例均符合典型阳生型特征;菖蒲、茭草光合能力略弱,部分指标符合阴生型特征。4种浮叶植物各指标均符合阳生型特征。实验推测,挺水植物和浮叶植物由于叶片所处环境不同,其光合适应机制存在明显分化。挺水植物叶片所处环境异质性较大,因而不同物种之间光合参数适应范围也大;浮叶植物叶片所处环境相对均一,因而光合参数差异也小。浮叶植物也不依赖NPQ进行高光保护。在湿地植被恢复工具种筛选过程中应综合考虑环境异质性和不同物种光适应能力的差异。     

土壤微生物削弱了水生-陆地系统补贴对植物生长的正向影响

土壤微生物削弱了水生-陆地系统补贴对植物生长的正向影响 水生-陆地系统补贴形成的联结作用在构建群落和调节生态系统功能方面发挥重要作用。在营养贫瘠的生态系统中(例如密歇根湖周围的淡水沙丘),水生-陆生系统补贴显得尤为重要。春季成年蠓在密歇根湖涌出,成群交配,然后死亡。蠓尸体在植物的基部形成土丘状,通过输入营养提高植物的生产力。然而,水生-陆地系统补贴对植物生产力的影响可能取决于其他生物的交互作用,特别是土壤微生物可能通过促进养分转化为植物可利用的形式或与植物竞争养分而发挥关键作用。在温室实验中,我们检验了湖生蠓(Chironomidae)的尸体和土壤微生物如何独立和相互影响一种常见沙丘草(沙拂子茅,Calamovilfa longifolia)的生长表现。为确定蠓是否影响土壤非生物特性,我们检验了添加蠓如何影响土壤养分和土壤湿度。研究结果显示,蠓极大地增加了植物生物量,但其效应的大小受土壤微生物的影响。在没有土壤微生物的情况下,添加蠓的植物生物量比没有添加的高7倍,而在有土壤微生物的情况下,植物生物量提高了3倍。蠓对植物生长的促进作用可能由于它们向土壤中输入养分所导致,因为与沙丘土壤相比,蠓的氮、磷、钾含量分别高100倍、10倍和150倍。我们的研究结果表明,土壤微生物可能与植物竞争这些养分。总之,我们发现蠓是重要的水生-陆地系统补贴,对密歇根湖沿岸植物生产力产生强烈和正向的影响,但水生-陆地系统补贴作用必须在生态群落内发生的复杂相互作用的背景下考虑。