The carbon cycle and CO2 over Phanerozoic time:: the role of land plants
The carbon cycle and CO2 over Phanerozoic time:: the role of land plants
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DOI：
10.1098/rstb.1998.0192
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发表时间：
1998-01-29
期刊：
影响因子：
--
通讯作者：
Berner, RA
中科院分区：
文献类型：
--
作者：
Berner, RA
建立了一个长期或数百万年的碳循环模型（GEOCARB），其中包括定量处理：(1)大陆上硅酸盐和碳酸盐岩的风化作用对大气CO2的吸收，以及海洋沉积物中碳酸盐矿物和有机物的沉积；(2)沉积岩中干酪根的风化作用以及碳酸盐和深部有机质的火山-变质-成岩分解所产生的脱气作用将CO2释放到大气中。敏感性分析表明，古生代维管植物的兴起是影响CO2的重要因素。泥盆纪二氧化碳的大幅下降主要是由于排水良好的高地土壤中深根植物的生长加速了硅酸盐岩石的风化作用。这种加速风化的定量影响是由目前的实地研究粗略估计的，在这些研究中，除了维管植物的存在与否之外，所有影响风化的因素都保持相对恒定。另一个重要的因素是沉积物中有机物的埋藏增强，这可能是由于产生了抗微生物的植物残骸（如木质素），从而使二氧化碳进一步下降到石炭纪和二叠纪。由GEOCARB模式计算的显生宙大气CO2水平与基于古土壤碳同位素组成测量和化石植物气孔指数的独立估计基本一致。二氧化碳水平与古气候估计的相关性表明，在过去6亿年里，大气温室效应一直是控制全球气候的一个主要因素。
A model (GEOCARB) of the long-term, or multimillion-year, carbon cycle has been constructed which includes quantitative treatment of (1) uptake of atmospheric CO2 by the weathering of silicate and carbonate rocks on the continents, and the deposition of carbonate minerals and organic matter in oceanic sediments; and (2) the release of CO2 to the atmosphere via the weathering of kerogen in sedimentary rocks and degassing resulting from the volcanic-metamorphic-diagenetic breakdown of carbonates and organic matter at depth.Sensitivity analysis indicates that an important factor affecting CO2 was the rise of vascular plants in the Palaeozoic. A large Devonian drop in CO2 was brought about primarily by the acceleration of weathering of silicate rock by the development of deeply rooted plants in well-drained upland soils. The quantitative effect of this accelerated weathering has been crudely estimated by present-day field studies where all factors affecting weathering, other than the presence or absence of vascular plants, have been held relatively constant. An important additional factor, bringing about a further CO2 drop into the Carboniferous and Permian, was enhanced burial of organic matter in sediments, due probably to the production of microbially resistant plant remains (e.g. lignin).Phanerozoic palaeolevels of atmospheric CO2 calculated from the GEOCARB model generally agree with independent estimates based on measurements of the carbon isotopic composition of palaeosols and the stomatal index for fossil plants. Correlation of CO2 levels with estimates of palaeoclimate suggests that the atmospheric greenhouse effect has been a major factor in controlling global climate over the past 600 million years.