Redox control on carbon mineralization and dissolved organic matter along a chronosequence of paddy soils
Redox control on carbon mineralization and dissolved organic matter along a chronosequence of paddy soils
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DOI：
10.1111/ejss.12042
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发表时间：
2013-08-01
影响因子：
4.2
通讯作者：
Kalbitz, K.
中科院分区：
文献类型：
--
作者：
Hanke, A.;Cerli, C.;Kalbitz, K.
水稻土受到周期性变化的氧化还原条件。为了更好地了解氧化还原对长期碳周转的控制作用，我们对沿着2000年水稻种植年代的水稻耕层土壤进行了碳矿化和溶解有机碳（DOC）的测定。非水稻土作为参照。在培养实验中，我们将土壤暴露于交替的氧化还原条件下12周。水稻土碳矿化与氧化还原条件无关。缺氧条件下造成增加DOC浓度的水稻土，可能是因为解吸引起的pH值增加。我们假设解吸释放旧的，以前稳定的碳，然后呼吸的微生物群落很好地适应缺氧条件。这一假设是支持的C-14签名的呼吸CO2，表明更大的矿化较旧的碳在缺氧条件下比在好氧条件下。缺氧条件下DOC浓度的增加并没有导致碳矿化的等价增加，可能是因为几乎没有可还原的氧化铁。因此，在缺氧条件下，净DOC和CO2的产生并不呈正相关。水稻土的碳矿化比非水稻土小20-75%，这是由于在好氧条件下呼吸作用较少。我们的结论是，在水稻以及在其他湿地土壤中的碳积累的结果，从微生物群落很好地适应缺氧条件下，但在矿化碳在短暂的好氧期效率较低。当缺氧条件下的矿化作用受到缺乏替代电子受体的限制时，碳的积累可能会更大。
Paddy soils are subjected to periodically changing redox conditions. In order to understand better the redox control on long-term carbon turnover, we assessed carbon mineralization and dissolved organic carbon (DOC) of paddy topsoils sampled along a chronosequence spanning 2000years of rice cultivation. Non-paddy soils were used as references. We exposed soils to alternating redox conditions for 12weeks in incubation experiments. Carbon mineralization of paddy soils was independent of redox conditions. Anoxic conditions caused increasing DOC concentrations for paddy soils, probably because of desorption induced by increasing pH. We assume desorption released older, previously stabilized carbon, which then was respired by a microbial community well adapted to anoxic conditions. This assumption is supported by the C-14 signatures of respired CO2, indicating larger mineralization of older carbon under anoxic than under oxic conditions. The increasing DOC concentrations under anoxic conditions did not result in an equivalent increase in carbon mineralization, possibly because of little reducible iron oxide. Therefore, net DOC and CO2 production were not positively related under anoxic conditions. The overall 20-75% smaller carbon mineralization of paddy soils than of non-paddy soils resulted from less respiration under oxic conditions. We conclude that carbon accumulation in paddy as well as in other wetland soils results from a microbial community well adapted to anoxic conditions, but less efficient in mineralizing carbon during transient oxic periods. Carbon accumulation might be even larger when mineralization under anoxic conditions is restricted by a lack of alternative electron acceptors.