Organic carbon fluxes and ecological recovery from the cretaceous-tertiary mass extinction

Differences between the carbon isotopic values of carbonates secreted by planktic and benthic organisms did not recover to stable preextinction levels for more than 3 million years after the Cretaceous-Tertiary mass extinction. These decreased differences may have resulted from a smaller proportion of marine biological production sinking to deep water in the postextinction ocean. Under this hypothesis, marine production may have recovered shortly after the mass extinction, but the structure of the open-ocean ecosystem did not fully recover for more than 3 million years.     

U/Pb zircon geochronology and tempo of the end-permian mass extinction

The mass extinction at the end of the Permian was the most profound in the history of life. Fundamental to understanding its cause is determining the tempo and duration of the extinction. Uranium/lead zircon data from Late Permian and Early Triassic rocks from south China place the Permian-Triassic boundary at 251.4 +/- 0.3 million years ago. Biostratigraphic controls from strata intercalated with ash beds below the boundary indicate that the Changhsingian pulse of the end-Permian extinction, corresponding to the disappearance of about 85 percent of marine species, lasted less than 1 million years. At Meishan, a negative excursion in delta13C at the boundary had a duration of 165,000 years or less, suggesting a catastrophic addition of light carbon.     

Geographic variation in the molluscan recovery from the end-cretaceous extinction

Biotic recovery patterns after the end-Cretaceous mass extinction differ among the molluscan faunas of the North American Gulf Coast, northern Europe, northern Africa, and Pakistan and northern India. In contrast to the Gulf Coast, the other three regions lack a rapid expansion and decline of "bloom taxa" and have lower proportions of invaders early in the recovery phase. The anomalous Gulf Coast patterns, distinct from extratropical Europe and the tropical regions, provide evidence for the biogeographic and macroevolutionary complexity of biotic recoveries and may have implications for present-day biotas.     

Large odd-numbered carbon clusters from fullerene-ozone reactions

The odd-numbered carbon clusters C(119), C(129), and C(139) have been observed in the mass spectra of toluene extracts of fullerene soots and of the products of ozone-fullerene reactions. Specifically, ozone-C(60) reactions yield C(119), ozone-C(70) reactions yield C(139), and ozone-(C(60)/C(70)) reactions produce C(119), C(129), and C(139). These unexpected species correspond to dimers of C(60), C(60)/C(70), and C(70), respectively, less one carbon atom, and are stable gas-phase ions with behavior similar to that of fullerenes. The results suggest a new route to functionalization and derivatization of fullerenes through controlled ozone-catalyzed cage-opening reactions.     

Reinforcement of competing behavior during extinction

Conditioned behavior declines in frequency when reinforcement is discontinued. In two experiments this extinction process was facilitated when competing behavior was reinforced as the original response was extinguished. When reinforcement for competing behavior was withdrawn, however, rats resumed their original behavior and there were no overall savings in total responses to extinction.     

Tropical forests and the global carbon cycle

New data on the three major determinants of the carbon release from tropical forest clearing are used in a computer model that simulates land use change and its effects on the carbon content of vegetation and soil in order to calculate the net flux of carbon dioxide between tropical ecosystems and the atmosphere. The model also permits testing the sensitivity of the calculated flux to uncertainties in these data. The tropics were a net source of at least 0.4 x 10(15) grams but not more than 1.6 x 10(15) grams of carbon in 1980, considerably less than previous estimates. Decreases in soil organic matter were responsible for 0.1 x 10(15) to 0.3 x 10(15) grams of the release, while the burning and decay of cleared vegetation accounted for 0.3 x 10(15) to 1.3 x 10(15) grams. These estimates are lower than many previous ones because lower biomass estimates and slightly lower land clearing rates were used and because ecosystem recovery processes were included. These new estimates of the biotic release allow for the possibility of a balanced global budget given the large remaining uncertainties in the marine, terrestrial, and fossil fuel components of the carbon cycle.     

中国滨海盐沼湿地碳收支与碳循环过程研究进展

滨海盐沼湿地由于其较高的初级生产力和较缓慢的有机质降解速率而成为缓解全球变暖的有效蓝色碳汇,近年来引起全球范围内的热切关注。我国滨海盐沼湿地分布较广,国内学者对滨海盐沼湿地碳循环及碳收支研究取得了一定进展,深入研究滨海盐沼湿地碳循环有助于对全球碳循环及全球变化的理解,并为利用滨海湿地进行碳的增汇减排提供科学依据。主要从我国滨海盐沼湿地碳循环主要观测方法、碳收支与碳循环过程及特点、碳库的组成与影响因素、气态碳的输入输出、潮汐作用对其碳收支的影响这5个方面出发,对国内的滨海盐沼湿地碳循环与碳收支的研究进展进行了归纳总结,并对今后的研究方向给出如下建议:(1)加强滨海盐沼湿地土壤碳库在深度上和广度上的研究;(2)标准化滨海盐沼湿地碳储量、碳通量的量化方法和观测技术;(3)在研究尺度上要宏观、微观并重,同时加强长期原位监测湿地碳通量的变化与室内模拟研究;(4)量化在潮汐影响下滨海盐沼湿地碳与邻近生态系统之间的横向交换通量。只有对我国滨海盐沼湿地碳库收支进行更准确的评估和长期的碳库动态变化监测,方可进一步认识我国盐沼湿地对全球气候变化的影响及其反馈作用,这对于预测全球变化及制定湿地碳储备功能的提升策略具有重要的意义。     

Use of carbon dioxide in enhanced oil recovery

Large volumes of oil will remain in U.S. oil reservoirs when standard recovery methods have been completed. Supercritical carbon dioxide can be used to recover part of that remaining oil. If carbon dioxide is dense enough, it extracts hydrocarbons from the oil to make a mixture miscible with crude oil. Such a mixture can recover 95 percent of the oil in controlled laboratory flow settings. Heterogeneity of reservoir rocks and the low viscosity of carbon dioxide reduce the fraction of oil recovered in projects to lower but still significant levels. With the construction of three pipelines to carry naturally occurring carbon dioxide from Colorado and New Mexico to Permian basin oil fields, large-scale implementation of enhanced oil recovery by carbon dioxide flooding is now beginning.     

Spontaneous whole brain slow potential changes during recovery from experimental neurosurgery

Prolonged, nonlocalized brain slow potential changes, frequently associated with cortical spreading depression, occur spontaneously during 5 days following brain implant surgery in rats. These potentials are accompanied by reductions in multiple nerve cell activity and reductions in behavioral motility. The method used in this study provides a tool for evaluating recovery from neurosurgical trauma or other brain injuries, and for testing procedures that facilitate or impede this process.     

1958-2008年太白山太白红杉林碳循环模拟

太白红杉(Larix chinensis林主要分布于我国秦岭太白山的林线位置,对气候变化的响应十分敏感.为了定量分析太白山太白红杉林在气候变化背景下的碳循环特征,基于模型(MTCLIM)模拟的温度和降水数据,应用植被动态过程模型(LPJ-GUESS)模拟了太白山南北坡1958-2008年太白红杉林的净初级生产力(NPP)、生物量和净生态系统碳交换量(NEE).结果表明:1)太白红杉和巴山冷杉(Abies fargesii)的NPP和生物量在太白红杉林占有优势,太白红杉的NPP和生物量均大于巴山冷杉.1958-2008年间太白红杉南北坡NPP的平均值为0.38 kgC·m-2·a-1,巴山冷杉为0.25 kgC·m-2,a-1,两者之和占整个太白红杉林NPP的86％;1958-2008年间太白红杉南北坡生物量的平均值为2.91 kgC/m2,巴山冷杉为2.02 kgC/m2,两者之和占太白红杉林生物量的94％.2)太白红杉和巴山冷杉的NPP均表现为北坡大于南坡,且南北坡均有逐年增加的趋势,北坡的增幅小于南坡,所以太白山南北坡太白红杉林的NPP差异有逐年减少的趋势.3)太白红杉生物量的年际波动较大,南北坡呈交替上升趋势,南坡的平均值(2.94 kgC/m2)大于北坡(2.89 kgC/m2).巴山冷杉生物量的年际波动相对较小,北坡生物量水平大于南坡.4)1958-2008年南北坡太白红杉林平均NEE均为-0.023 kgC·m-2·a-1,表现为碳汇.南北坡碳汇水平均呈逐年增加趋势,南坡的增加幅度(0.91 g·m-2·a-1)大于北坡(0.42 g·m-2·a-1).以气候和CO2为驱动因子对太白山太白红杉林的长期碳循环动态做了定量分析,从机理上揭示气候变化与生态系统碳循环的关系,还需要做进一步的野外观测和控制实验研究.     

The impact of agricultural soil erosion on the global carbon cycle

Agricultural soil erosion is thought to perturb the global carbon cycle, but estimates of its effect range from a source of 1 petagram per year(-1) to a sink of the same magnitude. By using caesium-137 and carbon inventory measurements from a large-scale survey, we found consistent evidence for an erosion-induced sink of atmospheric carbon equivalent to approximately 26% of the carbon transported by erosion. Based on this relationship, we estimated a global carbon sink of 0.12 (range 0.06 to 0.27) petagrams of carbon per year(-1) resulting from erosion in the world's agricultural landscapes. Our analysis directly challenges the view that agricultural erosion represents an important source or sink for atmospheric CO2.     

Feedback of speech muscle activity during silent reading: rapid extinction

Surface electromyograms of the laryngeal muscles were made while subjects read silently. Those who showed an increase in electrical activity over that at relaxation were provided with auditory feedback of the muscle activity.This treatment resulted in immediate and long-lasting cessation of the subvocalazation. This method should prove valuable in treating some reading problems.     

Dynamic complex formation during the yeast cell cycle

To analyze the dynamics of protein complexes during the yeast cell cycle, we integrated data on protein interactions and gene expression. The resulting time-dependent interaction network places both periodically and constitutively expressed proteins in a temporal cell cycle context, thereby revealing previously unknown components and modules. We discovered that most complexes consist of both periodically and constitutively expressed subunits, which suggests that the former control complex activity by a mechanism of just-in-time assembly. Consistent with this, we show that additional regulation through targeted degradation and phosphorylation by Cdc28p (Cdk1) specifically affects the periodically expressed proteins.     

土地利用和覆被变化对土壤碳库和碳循环的影响

土壤是陆地生态系统的重要组成成分,其较小幅度的变化即影响到陆地植被的养分供应,同时可能影响到碳向大气的排放而加剧全球气候变化。本文概述了国内外土壤碳库和碳吸存的研究概况,并对土地利用和覆被变化对土壤碳库和碳循环影响的最新研究进展进行了详尽的阐述,旨在对科学地利用和保护有限的土壤资源,减缓土壤中温室气体排放、增加土壤碳截存,提高土壤质量,对退化土地的生态恢复及环境治理和保护提供理论参考。     

草地碳循环遥感研究进展

【目的】草地生态系统是我国最大的陆地生态系统,对维护国家生态安全和畜牧业发展有重要作用。但我国草地类型多样、地理背景复杂、覆盖度低等特点制约了在大尺度上草地的高精度监测。卫星遥感技术的应用极大地提高了我国草地监测能力,在草地碳循环、生产力、生物量等方面得到了广泛应用。【方法】文章在回顾国内外草地碳循环遥感的最新进展基础上,从草地遥感观测手段、碳循环及其关键参数(初级生产力、生物量、叶面积指数、光合有效辐射分量、光能利用率和物候)反演等方面进行了总结,阐述了各种遥感影像在草地碳循环监测中的价值,对比和分析了草地关键参数遥感监测方法优缺点及应用前景。【结果】遥感技术的应用促进了草地碳循环监测能力的提升,结合遥感技术开展草地生态研究也是未来发展趋势。【结论】随着遥感数据的不断丰富和遥感建模及反演理论的深入发展,遥感手段将为草地生态系统研究及应用发挥更为重要的作用。     

突触素在动情周期大鼠子宫中的分布

【目的】研究突触素(SYP)在大鼠动情周期子宫内的分布情况及变化规律。【方法】选择健康、未产、体质量220~250 g成年雌性SD大鼠,采用阴道涂片法鉴定其动情周期,并采用免疫组化超敏SP(Streptavidin-Perox-idase,SP)法研究突触素在大鼠动情周期子宫内分布的变化规律。【结果】大鼠子宫各层组织中均有不同程度SYP免疫阳性产物的分布,并随动情周期的变化表现出一定规律:子宫内膜着色强弱各期差别不大,黏膜上皮细胞、腺上皮细胞及血管内皮细胞基本不着色或少许胞浆淡染,但其基底面均有较深SYP免疫阳性产物分布,动情前期着色最深,动情期、动情后期、动情间期依次减弱,后2期差别不明显;肌层和子宫外膜中,动情前期着色最深,动情期着色减弱,动情后期着色最浅,动情间期表达量明显回升,后3期与动情前期相比差异均极显著(P<0.01)。【结论】突触素在动情周期子宫中的分布表达具有一定的规律,可能受性类固醇激素的调节。