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【PNAS】区域甲烷排放 等
发布时间:2016-08-21  来源:土壤与农业可持续发展国家重点实验室  浏览:325

【早期维管植物对陆地的修饰 】Jinzhuang Xue et al. Belowground rhizomes in paleosols: The hidden half of an Early Devonian vascular plant. PNAS, 2016, doi: 10.1073/pnas.1605051113

Abstract

The colonization of terrestrial environments by rooted vascular plants had far-reaching impacts on the Earth system. However, the belowground structures of early vascular plants are rarely documented, and thus the plant−soil interactions in early terrestrial ecosystems are poorly understood. Here we report the earliest rooted paleosols (fossil soils) in Asia from Early Devonian deposits of Yunnan, China. Plant traces are extensive within the soil and occur as complex network-like structures, which are interpreted as representing long-lived, belowground rhizomes of the basal lycopsid Drepanophycus. The rhizomes produced large clones and helped the plant survive frequent sediment burial in well-drained soils within a seasonal wet−dry climate zone. Rhizome networks contributed to the accumulation and pedogenesis of floodplain sediments and increased the soil stabilizing effects of early plants. Predating the appearance of trees with deep roots in the Middle Devonian, plant rhizomes have long functioned in the belowground soil ecosystem. This study presents strong, direct evidence for plant−soil interactions at an early stage of vascular plant radiation. Soil stabilization by complex rhizome systems was apparently widespread, and contributed to landscape modification at an earlier time than had been appreciated.

  一项研究发现,来自一种早期维管植物的痕量的保存下来的植物物质提供了亚洲最早的有根的土壤床的证据。维管植物在陆地地形上的定植影响了大气和地质过程, 但是早期维管植物的地下结构在化石记录中的有限的呈现导致了对早期陆地生态系统的植物-土壤相互作用的不完整的理解。Jinzhuang Xue及其同事研究了来自中国云南的一个地质地层的年代测定为大约4.11亿年到4.08亿年前的早泥盆纪时期的河流沉积物样本。在这些土壤沉积物样本 中,这组科研人员发现了复杂的网络样结构,类似于一组已灭绝的早期维管植物的地下根状茎。使用土壤形态学和地球化学对这些沉积物样本进行的分析表明这些植 物材料很可能增加了土壤稳定性并且对该地区的土壤积累和形成有贡献。这组作者说,这些早期植物标本早于泥盆纪中期的深根树的出现,这提示维管植物的这些地 下结构可能在早期陆地生态系统中出现,而在维管植物陆地定植的一个早期阶段的植物-土壤相互作用对地球景观修饰的贡献可能比此前认为的更早。(来源:EurekAlert!)


【四角地区的甲烷排放】Christian Frankenberg et al. Airborne methane remote measurements reveal heavy-tail flux distribution in Four Corners region. PNAS, 2016, doi: 10.1073/pnas.1605617113

Abstract

Methane (CH4) impacts climate as the second strongest anthropogenic greenhouse gas and air quality by influencing tropospheric ozone levels. Space-based observations have identified the Four Corners region in the Southwest United States as an area of large CH4 enhancements. We conducted an airborne campaign in Four Corners during April 2015 with the next-generation Airborne Visible/Infrared Imaging Spectrometer (near-infrared) and Hyperspectral Thermal Emission Spectrometer (thermal infrared) imaging spectrometers to better understand the source of methane by measuring methane plumes at 1- to 3-m spatial resolution. Our analysis detected more than 250 individual methane plumes from fossil fuel harvesting, processing, and distributing infrastructures, spanning an emission range from the detection limit   2 kg/h to 5 kg/h through   5,000 kg/h. Observed sources include gas processing facilities, storage tanks, pipeline leaks, and well pads, as well as a coal mine venting shaft. Overall, plume enhancements and inferred fluxes follow a lognormal distribution, with the top 10% emitters contributing 49 to 66% to the inferred total point source flux of 0.23 Tg/y to 0.39 Tg/y. With the observed confirmation of a lognormal emission distribution, this airborne observing strategy and its ability to locate previously unknown point sources in real time provides an efficient and effective method to identify and mitigate major emissions contributors over a wide geographic area. With improved instrumentation, this capability scales to spaceborne applications [Thompson DR, et al. (2016) Geophys Res Lett 43(12):6571–6578]. Further illustration of this potential is demonstrated with two detected, confirmed, and repaired pipeline leaks during the campaign.

  科研人员报告了美国西南部四角地区的甲烷排放的空中测量的结果。太空中的观测已经识别出了四角区域是甲烷排放的一个主要来源。然而,这类测量的空间分辨率 不足以识别出单个点源。Christian Frankenberg及其同事使用1-3米空间分辨率的空中成像光谱仪,沿着科罗拉多-新墨西哥州边界的一个80X40平方千米的区域内实时探测单个甲 烷羽流。这组作者识别出了甲烷流量率范围在2-5千克/小时到大约5000千克/小时的245个点源。这些源包括石油天然气井场、管线泄漏、储存罐、天然 气处理设施以及一个煤矿通风竖井。地面团队通过热成像证实了管线泄漏并且把泄漏报告给了这些管线的运营者,后者进行了维修。来自所有观测到的点源的总流量 是每年0.23-0.39太克。这些流量率服从一个对数-正态分布,最高的10%的排放者排放量占该地区点源甲烷总排放量的大约一半。这组作者提出,空中 遥感测量可能是在大规模地理区域内识别出最大甲烷来源的一种有效方法,因此能改善缓解排放的举措。(来源:EurekAlert!)


【首批陆地植物与地球的氧浓度】Timothy M. Lenton et al. Earliest land plants created modern levels of atmospheric oxygen. PNAS, 2016, doi: 10.1073/pnas.1604787113

Abstract

The progressive oxygenation of the Earth’s atmosphere was pivotal to the evolution of life, but the puzzle of when and how atmospheric oxygen (O2) first approached modern levels (∼21%) remains unresolved. Redox proxy data indicate the deep oceans were oxygenated during 435–392 Ma, and the appearance of fossil charcoal indicates O2 >15–17% by 420–400 Ma. However, existing models have failed to predict oxygenation at this time. Here we show that the earliest plants, which colonized the land surface from ∼470 Ma onward, were responsible for this mid-Paleozoic oxygenation event, through greatly increasing global organic carbon burial—the net long-term source of O2. We use a trait-based ecophysiological model to predict that cryptogamic vegetation cover could have achieved ∼30% of today’s global terrestrial net primary productivity by ∼445 Ma. Data from modern bryophytes suggests this plentiful early plant material had a much higher molar C:P ratio (∼2,000) than marine biomass (∼100), such that a given weathering flux of phosphorus could support more organic carbon burial. Furthermore, recent experiments suggest that early plants selectively increased the flux of phosphorus (relative to alkalinity) weathered from rocks. Combining these effects in a model of long-term biogeochemical cycling, we reproduce a sustained +2‰ increase in the carbonate carbon isotope (δ13C) record by ∼445 Ma, and predict a corresponding rise in O2 to present levels by 420–400 Ma, consistent with geochemical data. This oxygen rise represents a permanent shift in regulatory regime to one where fire-mediated negative feedbacks stabilize high O2 levels.

  陆地植物的出现与进化可能解释一个长期的谜题,即地球大气是如何变得富氧的。双原子氧在大约24亿年前的大氧化事件中首次出现在了地球的大气中。尽管这种 变化改变了地球上的生命进化的道路,把氧增加到现代浓度的机制尚未得到解释。Tim Lenton及其同事提出,陆地植物的出现与进化,永久性地增加了有机碳埋藏,在大约4亿年前的一个第二次氧化事件中,把大气氧推高到了现代的浓度,这个 氧化事件建立了一个新的动态稳定状态。这组作者使用诸如苔藓和地衣等非维管植物物种的生态生理模型,证明了地球的早期植物生物圈的全球净初级生产力 (NPP)可能在大约4.45亿年前占了现代全球陆地净初级生产力(NPP)的大约30%。这组作者强化了这项发现从而考虑到早期苔藓植物的更高的氮-磷 比率;近来的发现提出,这些植物选择性地增加了岩石的磷风化。这组作者说,这种增强模型重现了符合地球化学记录的一个轨迹,其碳酸盐碳同位素记录在大约 4.45亿年前增加了大约千分之2,并且在4.2亿年到4亿年前氧相应地增加到了现代浓度。(EurekAlert!)


【植物与高渗胁迫】Aaron B. Stephan et al. Rapid hyperosmotic-induced Ca2+ responses in Arabidopsis thaliana exhibit sensory potentiation and involvement of plastidial KEA transporters. PNAS, 2016, doi: 10.1073/pnas.1519555113

Abstract

Plants experience hyperosmotic stress when faced with saline soils and possibly with drought stress, but it is currently unclear how plant roots perceive this stress in an environment of dynamic water availabilities. Hyperosmotic stress induces a rapid rise in intracellular Ca2+ concentrations ([Ca2+]i) in plants, and this Ca2+ response may reflect the activities of osmo-sensory components. Here, we find in the reference plant Arabidopsis thaliana that the rapid hyperosmotic-induced Ca2+ response exhibited enhanced response magnitudes after preexposure to an intermediate hyperosmotic stress. We term this phenomenon “osmo-sensory potentiation.” The initial sensing and potentiation occurred in intact plants as well as in roots. Having established a quantitative understanding of wild-type responses, we investigated effects of pharmacological inhibitors and candidate channel/transporter mutants. Quintuple mechano-sensitive channels of small conductance-like (MSL) plasma membrane-targeted channel mutants as well as double mid1-complementing activity (MCA) channel mutants did not affect the response. Interestingly, however, double mutations in the plastid K+ exchange antiporter (KEA) transporters kea1kea2 and a single mutation that does not visibly affect chloroplast structure, kea3, impaired the rapid hyperosmotic-induced Ca2+ responses. These mutations did not significantly affect sensory potentiation of the response. These findings suggest that plastids may play an important role in early steps mediating the response to hyperosmotic stimuli. Together, these findings demonstrate that the plant osmo-sensory components necessary to generate rapid osmotic-induced Ca2+ responses remain responsive under varying osmolarities, endowing plants with the ability to perceive the dynamic intensities of water limitation imposed by osmotic stress.

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