Global carbon export from the terrestrial biosphere controlled by erosion
Global carbon export from the terrestrial biosphere controlled by erosion
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DOI：
10.1038/nature14400
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发表时间：
2015-05-14
期刊：
影响因子：
64.8
通讯作者：
Eglinton, Timothy
中科院分区：
文献类型：
--
作者：
Galy, Valier;Peucker-Ehrenbrink, Bernhard;Eglinton, Timothy
河流向海洋输出颗粒有机碳（POC）在很宽的时间尺度上影响大气碳存量（1-5）。在地质时间尺度上，来自陆地生物圈的POC封存和岩石衍生（成岩）有机碳氧化之间的平衡决定了大气碳和氧库的大小（6，7）。在较短的时间尺度上，碳库（如土壤和海洋沉积物）之间交换速率的变化也会调节大气中的二氧化碳水平（1）。生物圈和岩石有机碳的各自的通量受到很大的限制，但是，控制POC输出的机制仍然难以捉摸，限制了我们的能力，定量预测POC通量的气候或构造变化的结果。在这里，我们估计生物圈和产岩POC通量的一套河流系统代表的集水区性质的自然变化。结果表明，无论是生物圈还是岩石源POC的输出量都与悬浮泥沙的输出量呈正相关，表明POC的输出主要受物理侵蚀的控制。使用全球汇编的测量悬浮沉积物通量，我们分别得出全球生物圈和岩石POC通量的估计值，分别为每年157（-50）（+74）和43（-25）（+61）兆吨碳。我们发现，生物圈POC输出主要是由河流的动员和运输POC的能力，在很大程度上是不敏感的陆地初级生产的大小。在全球范围内，物理侵蚀速率对海洋沉积物中生物圈POC埋藏速率的影响比通过硅酸盐风化作用的碳固存更大。我们的结论是，埋藏在海洋沉积物中的生物圈POC成为主导的长期大气二氧化碳汇增强的物理侵蚀。
Riverine export of particulate organic carbon (POC) to the ocean affects the atmospheric carbon inventory over a broad range of timescales(1-5). On geological timescales, the balance between sequestration of POC from the terrestrial biosphere and oxidation of rock-derived (petrogenic) organic carbon sets the magnitude of the atmospheric carbon and oxygen reservoirs(6,7). Over shorter timescales, variations in the rate of exchange between carbon reservoirs, such as soils and marine sediments, also modulate atmospheric carbon dioxide levels(1). The respective fluxes of biospheric and petrogenic organic carbon are poorly constrained, however, and mechanisms controlling POC export have remained elusive, limiting our ability to predict POC fluxes quantitatively as a result of climatic or tectonic changes. Here we estimate biospheric and petrogenic POC fluxes for a suite of river systems representative of the natural variability in catchment properties. We show that export yields of both biospheric and petrogenic POC are positively related to the yield of suspended sediment, revealing that POC export is mostly controlled by physical erosion. Using a global compilation of gauged suspended sediment flux, we derive separate estimates of global biospheric and petrogenic POC fluxes of 157(-50)(+74) and 43(-25)(+61) megatonnes of carbon per year, respectively. We find that biospheric POC export is primarily controlled by the capacity of rivers to mobilize and transport POC, and is largely insensitive to the magnitude of terrestrial primary production. Globally, physical erosion rates affect the rate of biospheric POC burial in marine sediments more strongly than carbon sequestration through silicate weathering. We conclude that burial of biospheric POC in marine sediments becomes the dominant long-term atmospheric carbon dioxide sink under enhanced physical erosion.