最近12 000年来青藏高原植被的时空分布

青藏高原30个点湖泊的孢粉记录综合研究显示: 在进入全新世之前(12 ka BP以前),除最东南部外,高原从东到西均发育为荒漠草原植被.全新世早期(12.0-9.0 ka BP)高原东南部(104°-98° E)为落叶阔叶林/针阔叶混交林; 中部(98°-92° E)为草甸或灌丛草甸,再向西至80° E左右为草原植被; 全新世中期(9.0-3.2 ka BP)高原由东向西古植被依次发育为针阔混交林和硬叶阔叶林(104°-98° E)→针阔混交林(98°-94° E)→灌丛草甸(94°-92° E)→草原(92°-80° E);全新世晚期(3.2 ka BP以后)由东向西古植被依次为硬叶阔叶林→针阔混交林→草甸→草原→荒漠.     

陇中黄土高原末次冰盛期以来的植被演替及其气候响应

末次冰盛期以来,地球系统经历了一次从冷到暖完整的气候旋回,是过去全球变化研究的一个重要时段。本文基于陇中黄土高原会宁硝沟剖面河湖相-水下黄土沉积序列的高分辨率地层孢粉记录,探讨该区末次冰盛期以来的植被演替及其气候响应模式,旨在为黄土高原生态环境建设的战略部署提供科学依据,且对进一步探讨区域气候演化机制、预测未来气候环境变化趋势具有重要意义。硝沟剖面的孢粉记录揭示,末次冰盛期以来该区的植被演替过程为:荒漠草原(寒冷的盛冰期)→针叶疏林/森林草原(逐渐增温的冰消期)→针阔叶混交林为主的森林草原→针阔叶混交林(温暖的盛间冰期)→针叶疏林草原→干草原/荒漠草原;相应的气候变化模式为:冷干→较温湿→较暖湿→暖湿→温凉偏干→较冷干。总体来看,末次冰盛期以来,研究区植被对气候环境变化的响应非常敏感,随着气候的冷暖干湿变化,森林/疏林草原带自东南-西北发生多次进退;区域顶极植物群落为中全新世气候最适宜期发育的针阔叶混交林,研究区早中全新世较长时期都有较大面积的针阔叶混交林发育;晚全新世植被退化为干草原/荒漠草原,一方面可能是气候持续变干的自然响应,另一方面可能也与此时强烈的人类活动对自然森林/草原植被的破坏导致的恶性循环有关。     

东北地区植被物候期遥感模拟与变化规律

使用1982—2003年GIMMS-NDVI数据,借助GIS空间分析功能,提取东北地区不同植被NDVI时间序列数据,使用分段式Logistic函数模拟了东北地区不同植被物候期,分析了1982—2003年不同植被物候期的变化趋势。结果表明:针叶林、阔叶林、草丛、草甸和沼泽植被生长季开始日期提前,生长季延长,其中沼泽植被生长季开始日期提前和生长季延长的趋势明显,针叶林次之;结束日期的变化趋势表现不一,针叶林和沼泽植被生长季结束日期推迟,阔叶林、草丛和草甸植被呈现微弱提前趋势;针阔混交林、灌丛、草原和农田植被生长季开始日期推迟,生长季缩短,其中农田植被生长季开始日期推迟和生长季缩短的趋势明显,草原次之;针阔混交林、灌丛、草原和农田4种植被生长季结束日期呈现提前的变化趋势,其中灌丛结束日期的提前趋势明显。     

浙江省生态公益林植被恢复过程中物种组成及多样性的变化

在浙江省生态公益林区域的现状植被中分析了6种主要群落类型的物种组成和多样性的变化格局,包括演替系列中的2种灌丛、松优势林、2种混交林和常绿阔叶林。结果表明含松较多的灌丛和松优势林常分布在环境退化较严重(土层瘠薄)的生境中,其中灌木层主要由阳性的映山红、木、白栎等组成,常绿阔叶林优势种木荷、青冈、苦槠、甜槠等在其中偶见,因此推断其自然恢复为常绿林的速度慢;含常绿阔叶树较多的灌丛及含松较少的混交林分布在土层较厚处,木荷、青冈、苦槠、甜槠等的频度和重要值都较大,较容易自然恢复为常绿阔叶林。各种群落中物种多样性指数——Gleason、Shannon-Wiener、Simpson指数基本上以常绿阔叶林为最高,其次是含松较少的混交林,含松较多的灌丛和松优势林各种多样性指数最低。本研究显示我国中亚热带东部森林植被恢复途径有3条:(1)灌草丛→针叶林(松)→针(松)阔混交林→常绿阔叶林;(2)灌草丛→针(松)阔混交林→常绿阔叶林;(3)灌草丛→常绿阔叶林。这意味着本区域的常绿阔叶林恢复可以不必经历松林阶段,在生境条件较好的地方通过人工干预、补种常绿阔叶树可以加速常绿阔叶林恢复。     

新疆巴里坤湖8.8cal.kaBP以来植被演替的花粉记录

本文利用新疆东部巴里坤盆地内巴里坤湖的地层孢粉记录,结合14C定年,重建了该地区8.8cal.kaBP以来植被的演化历史.结果表明在8.8-8.0cal.kaBP、8.0-4.3cal.kaBP、4.3-3.8cal.kaBP、3.8-0.6cal.kaBP以及0.6cal kaBP至今,植被分别经历了荒漠、荒漠草原/草原、荒漠、荒漠草原/草原再到荒漠的演化过程.研究区中全新世以来的这种植被变化模式与亚洲中部干旱区的其它研究记录具有很好的一致性.     

黄土高原西部4万多年以来植被与环境变化的孢粉记录

采集甘肃静宁、定西、秦安等地晚更新世晚期以来几个黄土剖面的孢粉样品,分别以晚更新世每个样品分辨率200—300年,全新世20—200年,揭示了黄土高原西部4万多年以来古植被曾经历过草原、森林草原(或疏林草原)、针叶林以及荒漠草原或荒漠几种植被的多次快速变化。在44.2—11kaBP期间,静宁地区植被主要表现为森林和草原成分的相互消长,其中44—29kaBP期间(MIS3)气候以湿润为主,发育针叶林,温度低于现在;23kaBP之后,气候冷干,以稀疏草原为主,在末次盛冰期植被甚至演化为荒漠草原。全新世大部分时间内是以草原或森林草原(或疏林草原)植被为主。在全新世中期,约7.6—5.8kaBP有近1700年时间发育有森林植被,在这个时期当地自然植被覆盖度较高,而草原或疏林草原发育时期植被往往较稀疏,反映气候相对干冷。根据出现的不同类型植物的孢粉浓度及其生态环境特性,研究区早、中全新世,约8.8—5.8kaBP沉积环境较湿润;自3.8kaBP以后气候环境总的变化趋势是逐渐变干,植被开始向草原荒漠化演变。然而,研究区整个全新世气候环境存在多次干湿交替现象,据孢粉记录,其中可能存在11次气候干寒事件。     

新疆乌伦古湖全新世以来高分辨率的孢粉记录与环境变迁

根据新疆乌伦古湖钻孔剖面高分辨率的孢粉研究,得出全新世以来研究区的气候经历了四个大的阶段：约9．99～7．72cal．kaBP期间,气候温暖干旱;7．72—3．62cal．kaBP,气候由温和偏湿逐渐转向温暖偏干;3．62—1．24cal．kaBP,气候由寒冷干旱逐渐转向寒冷偏湿到温和湿润;1．24cal．kaBP至今,气候总体上温和干旱。在这四个大阶段的气候背景下,还存在8．90cal．kaBP和8．35cal．kaBP左右、3．62—2．80cal．kaBP期间、0．82—0．45cal．kaBP期间和约0．23cal．kaBP时的突然变冷事件。本剖面的孢粉组合在约9．99—7．72cal．kaBP期间反映的是湖区的植被,早期为以芦苇为主的水生植物群落,随后演替成以黑三棱为主的水生植物群落;自7．72cal．kaBP以后,孢粉组合反映的是区域植被,与气候相应的区域植被依次经历了荒漠草原→荒漠→荒漠草原→草原或荒漠草原→草原→荒漠→荒漠草原的多次演替。     

藏北高原典型植被样区物候变化及其对气候变化的响应

植被物候作为陆地生态系统对气候变化的响应和反馈的重要指示,已成为区域或全球生态环境领域研究的热点。基于非对称高斯拟合方法重建了2001—2010年MODIS EVI时间序列影像,利用动态阈值法提取藏北高原植被覆盖2001—2010年每年关键物候参数。选取研究区内东部高寒灌丛草甸、中部高寒草甸及西部高寒草原和高寒荒漠4种典型植被类型,并结合附近的4个气象台站气候资料,分析典型植被物候在近10a对关键气候因子的响应特征。研究结果表明:(1)4种不同典型植被的物候特征(EVImax降低、返青期延后和生长季长度缩短)均表现出高寒灌丛草甸→高寒草甸→高寒草原→高寒荒漠草原的过渡;(2)藏北高原近10a的年平均气温及春、夏、冬三个季度的平均气温均呈显著升高的趋势,升温幅度在0.8—3.9℃/10a,降水减少趋势不显著,在这种水热条件下典型植被均表现出返青提前(7.2—15.5d/10a)、生长季延长(8.4—19.2d/10a)的趋势,而枯黄出现时间为年际间自然波动;(3)高寒灌丛草甸EVImax主要受春季降水量和气温影响,且降水的影响程度大于气温;对高寒草甸植被而言,春、夏季的气温和降水均有较大的影响;而高寒草原和高寒荒漠草原主要受夏季平均气温和降水量影响;(4)高寒灌丛草甸的返青时间主要受前一年秋季降水量的影响,相关系数达-0.579;而高寒草甸、高寒草原和高寒荒漠草原主要受春季平均气温影响,高寒荒漠草原的特征最为明显(r=-0.559)。     

河北小五台山主要植被类型的分布与地形的关系：基于遥感信息的分析

小五台山是河北省最高峰,具有较完整的暖温带植被垂直带谱。本文通过野外群落植被调查,结合由TM遥感影像解译1：50000地形图制作的DEM数据而得到的植被图,分析了小五台山主要植被群落的分布状况及其与地形的关系。结果表明,小五台山从低海拔到高海拔,依次出现灌丛、阔叶林、针阔混交林、暗针叶林、矮林、灌丛、草甸等植被类型。森林景观的面积最大,占总面积的60．7％;平均斑块面积最大的是阔叶林和亚高山草甸,斑块破碎化最严重的是水体和针阔混交林。不同的植被类型在不同的地形条件下分布特点不同,林地在北坡所占面积比例(占总面积的75％)远大于南坡(46%),说明水分条件是小五台山森林分布的限制因子之一;灌丛和草甸与林地相反。随海拔高度的变化,不同植被类型的分布面积比例发生变化,出现替代现象,形成植被垂直带谱。由于坡度的影响,增加了带谱内植被组成的复杂性。     

末次冰期以来湛江湖光岩玛珥湖孢粉记录及古环境变化

通过对湛江湖光岩玛珥湖钻孔孢粉记录的研究认为,末次冰期以来,该区植被类型从早期的南亚热带季风常绿阔叶林依次演替为,中亚热带常绿、落叶阔叶林→南亚热带季风常绿阔叶林→中亚热带常绿—落叶阔叶—针叶混交林(湖边草地)→热带季雨林→半常绿季雨林。气候最寒冷的时期温度比目前至少降低了4—6℃以上。全新世早期相对于旱。     

Ectogenesis and the case against the right to the death of the foetus

Ectogenesis, or the use of an artificial womb to allow a foetus to develop, will likely become a reality within a few decades, and could significantly affect the abortion debate. We first examine the implications for Judith Jarvis Thomson’s violinist analogy, which argues for a woman’s right to withdraw life support from the foetus and so terminate her pregnancy, even if the foetus is granted full moral status. We show that on Thomson’s reasoning, there is no right to the death of the foetus, and abortion is not permissible if ectogenesis is available, provided it is safe and inexpensive. This raises the question of whether there are persuasive reasons for the right to the death of the foetus that could be exercised in the context of ectogenesis. Eric Mathison and Jeremy Davis have examined several arguments for this right, doubting that it exists, while Joona Räsänen has recently criticized their reasoning. We respond to Räsänen’s analysis, concluding that his arguments are unsuccessful, and that there is no right to the death of the foetus in these circumstances.     

On the diversity of the Cladocera in the tropics

The mythical concept of an impoverished tropical cladoceran fauna is refuted. On a planetary scale, around half of the cladoceran species presently known occur exclusively in the tropics-subtropics, often with considerable restriction to particular geographical subzones. On a regional (political) scale, the situation is often unclear because of the continued fragmentary nature of studies, and because political units are not a good basis for biogeographical comparisons. At the finest level of resolution (lake-perlake comparisons), there appears to be an upper limit of c. 50 cladoceran species per individual lake. No significant difference between lakes in the temperate zone and in the tropics could be established here. Daphnia is largely absent from the tropics, but is replaced by more Sidids, Moinids, and Bosminids, such that the average cladoceran community in the limnetic zone of a tropical lake is not characterized by less species but rather by lower population densities. This, in turn, is considered a consequence of higher prevalent predation levels in the tropics.     

Tubular networks in the terminal endings of the visual receptor cells in the human,the monkey,the cat and the dog

Summary A tubular network was found in the terminal endings of the visual receptor cells in the human, the monkey (Macaca mulatta), the cat and the dog. These tubules are arranged in close groups in the vicinity of the synaptic lamellae and the invaginated dendrites. According to the form, diameter, density of the tubules and to the consistence of the network formed by them one can distinguish at these places an initial type (type I), a transitory (type II) and a vesicular one (type III). In the the type III branching, bizarre forms are frequent. The diameter of all the tubules reaches 500–600 Å, their density and walls being the same as in the synaptic vesicles.Similar networks also occur in the axons of the visual receptor cells of the monkey.

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Zusammenfassung In den Endigungen der Photorezeptorzellen von Mensch, Affe (Macaca mulatta), Katze und Hund kommen aus Tubuli bestehende Komplexe vor. Organellenartig in geschlossenen Gruppen angeordnet, liegen sie in Nähe der synaptischen Lamellen und der invaginierten Dendriten. An diesen Stellen kann man nach Form, Durchmesser, Dichte und Konsistenz der von den Tubuli gebildeten Komplexe drei Typen unterscheiden: 1. einen initialen (Typus I), 2. einen Übergangstypus (Typus II) und 3. einen vesiculären Typus (Typus III). In letzterem kommen häufig verzweigte, bizarre Formen vor. Der Durchmesser sämtlicher Tubuli erreicht 500–600 Å. Ihre Dichte und ihre Wand gleicht denen der synaptischen Vesikel.Ähnliche Komplexe fanden wir auch in den Axonen der Photorezeptorzellen vom Affen.

     

Assessing the Physiological State of the Fucoids from the Barents Sea Littoral by the End of the Polar Night

Methods of amperometry and potentiometric titration were used to follow dark respiration (DR) and apparent photosynthesis (AP) in the fucoids Ascophyllum nodosum (L.) Le Jol, Fucus vesiculosus L., and F. serratus L. from the Barents Sea littoral by the end of the 40-day-long polar night. The macroalgae were shown to manifest species-specific low rates of photosynthesis and respiration. However, in spite of their low photosynthetic status due to the effects of subzero temperature and prolonged low or zero illumination, the macroalgae have been able to restore DR and AP to the initial level already by the day 9; the ability to restore AP depended on the level of illumination. The study of the changes in the carbonate–bicarbonate system in the light and darkness demonstrated that the macroalgae grown in darkness, in contrast to those grown in twilight, could absorb bicarbonate in darkness; however, they lost this capacity after two-day-long illumination at an irradiance of 7 mol/(m² s). Bicarbonate uptake in darkness and the capacity to restore the systems of photosynthesis and respiration in fucoid cells are discussed in the context of algal energy metabolism under the polar night conditions.     

Arranging the elements of the potassium channel: the T1 domain occludes the cytoplasmic face of the channel

The voltage-gated potassium channel is currently one of the few membrane proteins where functional roles have been mapped onto specific segments of sequence. Although high-resolution structures of the transmembrane portions of three bacterial potassium channels, the tetramerization domain and the cytoplasmic ball are available, their relative spatial arrangement in mammalian channels remains a matter of ongoing debate. Cryo-electron microscopic images of the six transmembrane voltage-gated Kv channel have been reconstructed at up to 18 Å resolution, revealing that the T1 domain tetramerizes and is suspended below the transmembrane segments. However, the resolution of these images is insufficient to reveal the location of the third piece of the puzzle, the inactivating ball domain. We have used the aberrant interactions observed in a series of chimæric channels to establish that an assembled T1 domain restricts access to the cytoplasmic face of the channel, suggesting that the N-terminal ball and chain may be confined in the space between the T1 domain and the transmembrane portion of the channel.     

Separation of the pineal vesicle from the wall of the third ventricle during the post-hatching development of the chicken

Summary According to light- and electron-microscopic observations the pineal organ of the 3-day-old chicken consists of a prominent end vesicle and a tapering parenchymal stalk. During this stage the pineal lumen is in open communication with the third ventricle. However, in the 40-day-old chicken, which still possesses a well-developed end vesicle, the proximal portion of the pineal stalk displays regressive changes leading to local fragmentation. At this stage the pineal stalk is reduced, and the pineal lumen is missing. In 1-year-old chickens the parenchyma of the proximal portion of the stalk is further diminished, and in 3-year-old domestic fowl is completely displaced by bundles of collagenous fibers, only some nerve fibers being present. This post-hatching pineal development may reflect the sequence of changes leading from pineal sense organs to pineal glands.This work was supported by a grant-in-aid for Scientific Research from the Ministry of Education, Science and Culture of Japan     

On the Dependence of the Quadratic Risk of the Classical Predictor and the Prediction-Horizon

When constructing predictors on the basis of the linear model of time series of various indicators often the question arises on the dependence of forecasting accuracy and the changing prediction horizon. The dependency of the quadratic risk of the classical predictor and the time horizon is considered.     

中国植物区系与其它地区区系的联系及其在世界区系中的地位和作用

基于吴征镒将中国全部种子植物３２３８个属的分布区划分为１５个大类型和３４个变型的基础上,简要地讨论了中国植物区系与其它地区区系的联系,以及它在被子植物起源方面的作用。主要论点如下：（１）与热带亚洲区系的联系。这种联系主要通过第７类型（热带亚洲分布）及其５个变型来体现的。本文列举了１０个科,龙脑香料、狭义隐翼科、交让木科、五隔草科、五列木科、肉实树科、心翼果科、八宝树科、兰花蕉科和四数木科,来说明这