Microbial formation of stable soil carbon is more efficient from belowground than aboveground input
Microbial formation of stable soil carbon is more efficient from belowground than aboveground input
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DOI：
10.1038/s41561-018-0258-6
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发表时间：
2018-11
影响因子：
18.3
通讯作者：
N. Sokol;M. Bradford
中科院分区：
文献类型：
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作者：
N. Sokol;M. Bradford
地上与地下植物碳输入对稳定土壤有机碳库的相对贡献是争论的主题，直接影响到碳循环的建模和管理。地下根际途径（即离开活根的碳）理论上比地上途径更有效地形成稳定的土壤碳。然而，虽然有几种机制被用来解释这种效率，很少有经验测试或量化。在这里，我们使用具有标准化碳输入的土壤微观世界来研究三种假设的机制，这些机制将溶解有机碳的地上输入途径与地下输入途径区分开来-通过微生物生物量-到矿物稳定的土壤有机碳库：（1）移动的物理距离，（2）碳化合物进入区域的微生物丰度（3）碳输送的频率和体积（即，不频繁的“脉冲”与频繁的“滴”）。我们表明，通过微生物形成途径，地下输入形成矿物稳定的土壤碳比地上输入更有效，部分原因是根际微生物群落相对于散装土壤群落的形成效率更高。然而，我们表明，由于散装土壤具有更大的能力，形成矿物稳定的土壤碳，由于其更大的总体积，地上与地下碳输入的相对贡献强烈地依赖于根际土壤散装的比例。
The relative contributions of aboveground versus belowground plant carbon inputs to the stable soil organic carbon pool are the subject of much debate—with direct implications for how the carbon cycle is modelled and managed. The belowground rhizosphere pathway (that is, carbon exiting the living root) is theorized to form stable soil carbon more efficiently than the aboveground pathway. However, while several mechanisms have been invoked to explain this efficiency, few have been empirically tested or quantified. Here, we use soil microcosms with standardized carbon inputs to investigate three posited mechanisms that differentiate aboveground from belowground input pathways of dissolved organic carbon—through the microbial biomass—to the mineral-stabilized soil organic carbon pool: (1) the physical distance travelled, (2) the microbial abundance in the region in which a carbon compound enters (that is, rhizosphere versus bulk soil) and (3) the frequency and volume of carbon delivery (that is, infrequent ‘pulse’ versus frequent ‘drip’). We demonstrate that through the microbial formation pathway, belowground inputs form mineral-stabilized soil carbon more efficiently than aboveground inputs, partly due to the greater efficiency of formation by the rhizosphere microbial community relative to the bulk soil community. However, we show that because the bulk soil has greater capacity to form mineral-stabilized soil carbon due to its greater overall volume, the relative contributions of aboveground versus belowground carbon inputs depend strongly on the ratio of rhizosphere to bulk soil.