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Welp LR Keeling RF Meijer HA Bollenbacher AF Piper SC Yoshimura K Francey RJ Allison CE Wahlen M 《Nature》2011,477(7366):579-582
The stable isotope ratios of atmospheric CO(2) ((18)O/(16)O and (13)C/(12)C) have been monitored since 1977 to improve our understanding of the global carbon cycle, because biosphere-atmosphere exchange fluxes affect the different atomic masses in a measurable way. Interpreting the (18)O/(16)O variability has proved difficult, however, because oxygen isotopes in CO(2) are influenced by both the carbon cycle and the water cycle. Previous attention focused on the decreasing (18)O/(16)O ratio in the 1990s, observed by the global Cooperative Air Sampling Network of the US National Oceanic and Atmospheric Administration Earth System Research Laboratory. This decrease was attributed variously to a number of processes including an increase in Northern Hemisphere soil respiration; a global increase in C(4) crops at the expense of C(3) forests; and environmental conditions, such as atmospheric turbulence and solar radiation, that affect CO(2) exchange between leaves and the atmosphere. Here we present 30 years' worth of data on (18)O/(16)O in CO(2) from the Scripps Institution of Oceanography global flask network and show that the interannual variability is strongly related to the El Ni?o/Southern Oscillation. We suggest that the redistribution of moisture and rainfall in the tropics during an El Ni?o increases the (18)O/(16)O ratio of precipitation and plant water, and that this signal is then passed on to atmospheric CO(2) by biosphere-atmosphere gas exchange. We show how the decay time of the El Ni?o anomaly in this data set can be useful in constraining global gross primary production. Our analysis shows a rapid recovery from El Ni?o events, implying a shorter cycling time of CO(2) with respect to the terrestrial biosphere and oceans than previously estimated. Our analysis suggests that current estimates of global gross primary production, of 120 petagrams of carbon per year, may be too low, and that a best guess of 150-175 petagrams of carbon per year better reflects the observed rapid cycling of CO(2). Although still tentative, such a revision would present a new benchmark by which to evaluate global biospheric carbon cycling models. 相似文献
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LJ. Kržalić V. Mandić LJ. Mihailović 《Cellular and molecular life sciences : CMLS》1962,18(8):368-369
Résumé Les auteurs ont déterminé par la méthode de la chromatographie à deux dimensions, la teneur en glutamine et en acide -aminobutyrique des différentes parties du cerveau du chat. La concentration la plus élevée de l'acide -aminobutyrique a été trouvé dans l'hypothalamus, tandis que celle de la glutamine a été constatée dans le noyau caudé. Les concentrations les plus basses de ces deux protéines apparaissent dans la substance blanche du cerveau. 相似文献
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“数字地球”作为新世纪信息时代的新目标和制高点,必将在西部大开发战略的实施过程中起到至关重要的作用。从“数字地球”的基本概念出发,应用“数字地球”的理论和技术,阐述了“数字地球”技术对西部大开发的战略意义和应用方向,为我国西部地区的可持续发展提供了新的思路和技术方法。 相似文献
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MA Deardorff M Bando R Nakato E Watrin T Itoh M Minamino K Saitoh M Komata Y Katou D Clark KE Cole E De Baere C Decroos N Di Donato S Ernst LJ Francey Y Gyftodimou K Hirashima M Hullings Y Ishikawa C Jaulin M Kaur T Kiyono PM Lombardi L Magnaghi-Jaulin GR Mortier N Nozaki MB Petersen H Seimiya VM Siu Y Suzuki K Takagaki JJ Wilde PJ Willems C Prigent G Gillessen-Kaesbach DW Christianson FJ Kaiser LG Jackson T Hirota ID Krantz K Shirahige 《Nature》2012,489(7415):313-317
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