Nitrogen fixation in marine shipworms

Nitrogen fixation is associated with four shipworl species. A bacterium capable of fixing nitrogen under anaerobic conditions and of liquefying cellulose in culture has been isolated from the gut of one species. High fixation rates (up to 1.5 micrograms of nitrogen per milligram dry weight per hour), which resulted in a doubling of cellular nitrogen in as little as 1.4 days, was associated with Teredora malleolus from the Sargasso Sea. Three species from coastal waters were assayed, and of these juveniles showed the highest fixation rates. Nitrogen fixation activity appeared to be inversely related to the ability of shipworms to obtain combined-nitrogen compounds in their diet. It could be a significant source of nitrogen for shipwornms and perhaps other oceanic organisms that ingest terrestrial plant material.     

A Chemoautotrophically Based Cave Ecosystem

Microbial mats discovered in a ground-water ecosystem in southern Romania contain chemoautotrophic bacteria that fix inorganic carbon, using hydrogen sulfide as an energy source. Analysis of stable carbon and nitrogen isotopes showed that this chemoautotrophic production is the food base for 48 species of cave-adapted terrestrial and aquatic invertebrates, 33 of which are endemic to this ecosystem. This is the only cave ecosystem known to be supported by in situ autotrophic production, and it contains the only terrestrial community known to be chemoautotrophically based.     

鄱阳湖湿地两种优势植物叶片C、N、P动态特征

2011年2—6月在鄱阳湖南矶湿地国家级自然保护区逐月测定了灰化苔草(Carex cinerascens)、南荻(Triarrhena lutarioriparia)叶片C、N、P含量及其地上生物量，以阐明鄱阳湖湿地优势植物C、N、P含量及化学计量比动态特征与控制因子，探讨湿地养分利用与限制状况。结果表明：1）两种优势植物叶有机碳含量变化范围分别为365.3—386.6 mg/g和352.6—393.2 mg/g，平均值(?标准差)分别为(375.5?17.4) mg/g和(371.7?12.5) mg/g；叶N含量分别为6.96—17.59 mg/g和5.50—20.68 mg/g，平均值分别为(11.35?1.40) mg/g和(11.54?0.84) mg/g；叶P含量变化范围为0.65—2.14 mg/g和0.57—2.25 mg/g，平均含量为(1.56?0.69) mg/g和(1.55?0.68) mg/g。两种植物C:N、C:P、N:P平均值分别为37.65、413.60、9.62和41.05、410.29、9.57，C、N、P及其化学计量比种间差异不显著(P>0.05)。2）气温与地上生物量是N、P及其化学计量比季节变化的主要控制因子，气温和生物量对两种优势植物叶片氮、磷含量的影响要高于对叶有机碳含量的影响。3）植物C:N、C:P与地上生物量变化趋势基本一致，显示N、P养分利用效率随植物的快速生长而提高；根据两种优势植物及土壤N、P含量与化学计量比来判断，研究区植物更多地受氮限制。     

Solar wind record on the moon: deciphering presolar from planetary nitrogen

Ion microprobe analyses show that solar wind nitrogen associated with solar wind hydrogen implanted in the first tens of nanometers of lunar regolith grains is depleted in 15N by at least 24% relative to terrestrial atmosphere, whereas a nonsolar component associated with deuterium-rich hydrogen, detected in silicon-bearing coatings at the surface of some ilmenite grains, is enriched in 15N. Systematic enrichment of 15N in terrestrial planets and bulk meteorites relative to the protosolar gas cannot be explained by isotopic fractionation in nebular or planetary environments but requires the contribution of 15N-rich compounds to the total nitrogen in planetary materials. Most of these compounds are possibly of an interstellar origin and never equilibrated with the 15N-depleted protosolar nebula.     

沼泽湿地土壤氮矿化对温度变化及冻融的响应

通过室内控制培养试验方法,研究了不同温度和冻融循环过程对沼泽湿地土壤有机氮矿化影响.结果表明,湿地土壤中无机氮以铵态氮为主,温度和培养时间显著影响土壤有机氮的矿化,在温度-25～30℃之间,N的矿化速率、硝化速率随温度增加而增加,30℃时矿化速率(1.17mg·k-1·d-1)和硝化速率(0.79mg·k-1·d-1)最大.沼泽湿地土壤有机氮矿化培养时间以4～5周较为适宜.冻结温度和冻融次数显著影响土壤有机氮矿化过程,且-25～5℃冻融循环比-5～5℃冻融循环矿化累积量高.冻融循环促进了土壤有机氮的矿化,有利于土壤中有效氮的累积,为春季植物生长提供足够的氮素,对维持生态系统稳定有重要意义.     

不同生态系统土壤可溶性有机氮（SON）的研究

土壤可溶性有机氮在氮的生物地球化学循环和陆地生态系统氮循环中起着重要作用。对近年来国内外有关不同生态系统土壤可溶性有机氮的来源组成、含量、化学本质以及在氮循环、转化中的作用进行综述,并对今后的研究工作进行了展望,为进一步开展不同生态系统土壤可溶性有机氮研究提供依据。     

Robinson B: Attack autotomy: a defense against predators

The response of five species of crabs to simulated predator attack was examined. Two terrestrial species autotomized their chelipeds after the chelae were firmly attached to the predator. Selection for attack autotomy is balanced by selection for retention of the cheliped whenever the cheliped is important in social or maintenance functions.     

Nitrogen fixation in the marine environment

Cyanobacteria of the genus Oscillatoria (Trichodesmium) account for annual inputs of nitrogen to the world's oceans of about 4.8 x 10(12) grams while benthic environments contribute 15 x 10(12) grams. The sum of these inputs is one-fifth of current estimates of nitrogen fixation in terrestrial environments and one-half of the present rate of industrial synthesis of ammonia. When the total of all nitrogen inputs to the sea is compared with estimated losses through denitrification, the marine nitrogen cycle approximates a steady state. Oceanic nitrogen fixation can supply less than 0.3 percent of the calculated demand of marine phytoplankton. The minor contribution by nitrogen fixation to the overall nitrogen economy of the sea is not consistent with the supposition that nitrogen is the primary limiting nutrient and suggests that factors other than nitrogen availability limit phytoplankton growth rates.     

重庆合川市陆生野生脊椎动物资源调查报告

对重庆合川市进行了陆生野生脊椎动物资源调查,发现陆生野生脊椎动物29种,结合有关文献,共记载该地区动物105种,隶属于21目44科72属。其中,两栖类9种(2目5科7属),爬行类14种(2目5科13属),鸟类67种(13目26科40属),兽类15种(4目7科12属)。这4类动物分别占该类动物全国种类数的4.59%,4.38%,5.65%和3.33%。对该地区野生动物资源现状、生境状况、利用状况和保护管理现状进行了分析评价。     

美洲商陆和拉巴豆在不同氮磷肥组合下的竞争效应

以美洲商陆(Phytolacca americana)和拉巴豆(Dolichos lablab)为试验材料,通过室外盆栽试验,研究它们在不同氮磷施肥组合(低氮、高氮、低磷、高磷、低氮低磷、低氮高磷、高氮低磷、高氮高磷)下的竞争效应。结果表明：拉巴豆单种及与美洲商陆混种中,施磷肥和混合施肥均显著提高拉巴豆叶的生物量和总生物量;美洲商陆单种及与拉巴豆混种中,高氮和高氮高磷处理均显著提高美洲商陆的株高、根生物量和总生物量;单种时,高氮高磷肥力处理下美洲商陆叶磷含量、根氮含量和根磷含量显著高于对照;混种时,在高氮高磷肥力处理下美洲商陆叶磷含量、根氮含量和根磷含量显著低于对照;拉巴豆单种及与美洲商陆混种时,拉巴豆叶氮含量、根氮含量均在高氮高磷肥力处理下达到最高,叶氮含量分别为67.17、66.62,根氮含量分别为62.07、66.31 mg/g;美洲商陆与拉巴豆混种时,在所有施肥处理下美洲商陆的相对产量均小于1.0,说明拉巴豆对美洲商陆有明显的种间竞争抑制作用。     

贵州东北部五县陆生贝类资源调查及区系分析*(腹足纲:前鳃亚纲,肺螺亚纲)

笔者对贵州省东北部地区进行了陆生贝类资源调查,获得陆生贝类标本6000多号.经鉴定得69种,分隶于12科31属.区系分析表明:黔东北部地区的陆生贝类以东洋界西南区种类和华中区种类为优势.在69种中,有30种分布于华中区和西南区,约占总数的43.48%;有13种分布于华南区、华中区和西南区(即东洋界),约占总数的18.84%;有9种仅分布于华中区,约占总数的13.04%.将本调查结果与贵州南部地区陆生贝类物种进行比较,发现两地的种类差异明显.     

区域土壤有机氮迁移的研究进展

农田土壤氮素迁移是影响区域环境质量的重要过程。通过综述近期在区域有机氮迁移以及稳定性同位素和模型研究方法方面的进展,指出:我国有机氮源的氮素损失在人口稠密和养殖业发达的区域已经成为非点源污染的重要来源;小流域氮素输出中可溶性有机氮是一个重要组成,其输出过程受气候以及人为引起的植被、土壤及水文过程的变化的影响;稳定性氮氧同位素可以识别水体中陆源氮污染物的分布;基于GIS的过程模型可以定量分析区域氮素迁移的数量及其环境效应。进一步提出了目前需要加强农田有机氮迁移过程及其影响机制的研究,发展基于稳定性同位素的区域氮素迁移定量方法,建立稻田生态系统和水旱轮作系统的氮素迁移定量评价模型,并归纳了减少面源污染的区域氮素迁移调控措施。     

雅安十三种软体动物体内吸虫幼虫期的调查研究

1989年3-9月作者检查雅安9种淡水软体动物11838只,4种陆生软体动物790只,从中查出21种吸虫的胞蚴(或雷蚴)和尾蚴期。通过本次调查发现11种吸虫的中间宿主(或第一中间宿主)新记录共15个,文中对赤豆螺与人和动物间的相互关系作了讨论。     

Effects of trace gases and water vapor on the diffusion coefficient of polonium-218

The two-filter method described by Thomas and LeClare was used to investigate the effects of trace concentrations of nitric oxide and nitrogen dioxide in dry nitrogen on the diffusion coefficient of radium A (polonium-218). Charged radium A was neutralized in 10 parts per million (ppm) nitrogen dioxide in dry nitrogen, in 8.3 ppm nitric oxide in dry 92 percent nitrogen and 8 percent oxygen, and in nitrogen with 20 and 80 percent relative humidity. No neutralization was seen in dry nitrogen, dry oxygen, dry air, or 10 ppm nitric oxide in dry nitrogen. The diffusion coefficient of the neutral radium A species was found to be 0.079 square centimeters per second, regardless of the relative humidity of the nitrogen gas atmosphere. Lower values were observed for charged species.     

低氮磷胁迫对五个玉米品种幼苗的影响

为了探求低氮、磷胁迫对玉米幼苗的影响,在不同低氮、磷间进行组合,对金穗98、先玉508、三峡玉9号、高瑞171和金13-2 5个玉米品种幼苗在低氮、磷胁迫下的丙二醛、可溶性糖、过氧化氢酶、过氧化物酶和超氧化物歧化酶5个指标进行检测。结果表明,氮和磷元素缺乏程度与由此而造成的损伤直接相关;不同氮、磷缺乏的胁迫对玉米幼苗的损伤呈现波动性变化,不同组合对所测定各生化指标的影响及程度不同;在不同氮、磷缺乏组合下,5个品种所观察各指标数值的变化趋势基本一致,但不同品种间数值大小存在差异。对生长逆境敏感的生理和生化指标的分析显示,最耐氮、磷缺乏的是先玉508,而三峡玉9号和金穗98对氮、磷缺乏较为敏感。     

Climatic niche shifts are rare among terrestrial plant invaders

The assumption that climatic niche requirements of invasive species are conserved between their native and invaded ranges is key to predicting the risk of invasion. However, this assumption has been challenged recently by evidence of niche shifts in some species. Here, we report the first large-scale test of niche conservatism for 50 terrestrial plant invaders between Eurasia, North America, and Australia. We show that when analog climates are compared between regions, fewer than 15% of species have more than 10% of their invaded distribution outside their native climatic niche. These findings reveal that substantial niche shifts are rare in terrestrial plant invaders, providing support for an appropriate use of ecological niche models for the prediction of both biological invasions and responses to climate change.     

Apollo 16 far-ultraviolet camera/spectrograph: Earth observations

A far-ultraviolet camera/spectograph experiment was operated on the lunar surface during the Apollo 16 mission. Among the data obtained were images and spectra of the terrestrial atmosphere and geocorona in the wavelength range below 1600 angstroms. These gave the spatial distributions and relative intensities of emissions due to atomic hydrogen, atomic oxygen, molecular nitrogen, and other species-some observed spectrographically for the first time.     

输变电工程对陆生脊椎动物的影响和保护措施

对四川雅安至安徽皖南1 000 kV交流特高压输变电工程项目沿线的陆生脊椎动物进行实地调查,分析了输变电工程的建设期和运营期对陆生脊椎动物的影响,并提出了相应的保护措施和建议。结果表明,在工程区域范围内共记录陆生脊椎动物4纲32目89科,502种;输变电工程建设、营运过程中会破坏动物的栖息地,造成陆生脊椎动物的直接死亡,使得大部分陆生脊椎动物迁移到其他地方,远离施工区范围。同时,对动物的觅食、生殖等活动都构成不同程度的影响。通过实行有效的保护措施以及陆生脊椎动物自身的调节能力能将影响降至最小。     

草地土壤微生物及酶活性对氮沉降的响应研究进展

区域性的氮沉降增加近年来受到广泛关注,有研究预测在未来的几十年内陆地表面的活性氮沉降量会不断增加。 草地作为陆地生态系统分布最广的植被,更易受氮沉降增加的干扰。土壤微生物能够影响土壤生态系统的结构、功能及过程,是维持土壤生产力的重要组分。因此,本文综述了氮沉降增加对草地土壤微生物及细胞外酶活性的影响研究进展,并对未来研究进行展望,以期为未来相关研究提供一些参考。     

Habitat split and the global decline of amphibians

The worldwide decline in amphibians has been attributed to several causes, especially habitat loss and disease. We identified a further factor, namely "habitat split"-defined as human-induced disconnection between habitats used by different life history stages of a species-which forces forest-associated amphibians with aquatic larvae to make risky breeding migrations between suitable aquatic and terrestrial habitats. In the Brazilian Atlantic Forest, we found that habitat split negatively affects the richness of species with aquatic larvae but not the richness of species with terrestrial development (the latter can complete their life cycle inside forest remnants). This mechanism helps to explain why species with aquatic larvae have the highest incidence of population decline. These findings reinforce the need for the conservation and restoration of riparian vegetation.