Mineral protection of soil carbon counteracted by root exudates
Mineral protection of soil carbon counteracted by root exudates
复制标题
DOI：
10.1038/nclimate2580
复制
发表时间：
2015-06-01
影响因子：
30.7
通讯作者：
Kleber, Markus
中科院分区：
文献类型：
--
作者：
Keiluweit, Marco;Bougoure, Jeremy J.;Kleber, Markus
多条现有证据表明，气候变化促进了有机化合物向土壤中的根部分泌物。最近的实验研究表明，渗出液输入的增加可能会导致土壤碳的净损失。这种对微生物碳矿化的刺激(“启动”)通常被认为是合理的，因为渗出物为本地土壤碳的分解(共代谢)提供了容易的生物可用能量供应。在这里，我们展示了另一种机制可以导致相同或更大程度的碳损失。我们发现，一种常见的根分泌物草酸，通过从与矿物质的保护性结合中释放有机化合物来促进碳损失。通过促进微生物获得以前受矿物保护的化合物，这种间接机制加速了碳损失，而不仅仅是增加了能量上更有利的底物的供应。我们的结果为“引发”现象背后的生物-非生物耦合机制提供了见解，并挑战了矿物相关碳在千年时间尺度上免受微生物循环影响的假设。
Multiple lines of existing evidence suggest that climate change enhances root exudation of organic compounds into soils. Recent experimental studies show that increased exudate inputs may cause a net loss of soil carbon. This stimulation of microbial carbon mineralization ('priming') is commonly rationalized by the assumption that exudates provide a readily bioavailable supply of energy for the decomposition of native soil carbon (co-metabolism). Here we show that an alternate mechanism can cause carbon loss of equal or greater magnitude. We find that a common root exudate, oxalic acid, promotes carbon loss by liberating organic compounds from protective associations with minerals. By enhancing microbial access to previously mineral-protected compounds, this indirect mechanism accelerated carbon loss more than simply increasing the supply of energetically more favourable substrates. Our results provide insights into the coupled biotic-abiotic mechanisms underlying the 'priming' phenomenon and challenge the assumption that mineral-associated carbon is protected from microbial cycling over millennial timescales.