A proposed mechanism for the pulse in carbon dioxide production commonly observed following the rapid rewetting of a dry soil
A proposed mechanism for the pulse in carbon dioxide production commonly observed following the rapid rewetting of a dry soil
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DOI：
10.2136/sssaj2003.0798
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发表时间：
2003-05-01
影响因子：
2.9
通讯作者：
Schimel, JP
中科院分区：
文献类型：
--
作者：
Fierer, N;Schimel, JP
干燥土壤的快速再湿润通常会产生持续2至6天的土壤二氧化碳脉冲。这种现象在表层土壤中很常见，但产生二氧化碳脉冲的机制尚未得到明确确定。我们研究了单一干燥和再湿润事件对土壤C库的影响，以确定哪些特定的C底物被矿化以产生所观察到的呼吸速率脉冲。我们用C-14-葡萄糖标记了两种土壤，并测量了在干燥和再湿循环过程中释放的CO2、可提取生物量C和可提取土壤有机质（SOM-C）的富集程度和池大小。再湿润后，呼吸速率比干燥前测量的速率高475 - 370%。释放CO2的富集程度是可提取生物量C库富集程度的1 ~ 2倍，是可提取有机C富集程度的10 ~ 20倍，表明CO2脉冲完全是由微生物生物量C的矿化产生的。然而，没有证据表明微生物细胞在再润湿过程中有大量裂解。我们假设二氧化碳的脉冲是由高度富集的细胞内化合物的快速矿化产生的，这是微生物生物量对土壤水势快速增加的响应。干燥和再湿过程也会释放出受物理保护的SOM，使可提取的SOM- c量增加了200%。通过再润湿事件变得可溶的额外SOM-C对再润湿CO2脉冲没有实质性的贡献。总的来说，干燥土壤的快速再湿润可以在短期内通过增加细胞质溶质的微生物矿化来影响土壤C循环，而在长期内通过减少微团聚体中物理保护的SOM总量来影响土壤C循环。
The rapid rewetting of a dry soil often yields a pulse in soil CO2 production that persists for 2 to 6 d. This phenomenon is a common occurrence in surface soils, yet the mechanism responsible for producing the CO2 pulse has not been positively identified. We studied the effects of a single drying and rewetting event on soil C pools, to identify which specific C substrates are mineralized to produce the observed pulse in respiration rates. We labeled two soils with C-14-glucose and measured the enrichment and pool sizes of the released CO2, extractable biomass C, and extractable soil organic matter (SOM-C) throughout a drying and rewetting cycle. After rewetting, respiration rates were 475 to 370% higher than the rates measured before the dry down. The enrichment of the released CO2 was 1 to 2 times higher than the enrichment of the extractable biomass C pools and 10 to 20 times higher than the enrichment of the extractable organic C, suggesting that the CO2 pulse was generated entirely from the mineralization of microbial biomass C. However, there was no evidence of substantial microbial cell lysis on rewetting. We hypothesize that the pulse of CO2 is generated by the rapid mineralization of highly enriched intracellular compounds as a response by the microbial biomass to the rapid increase in soil water potentials. The drying and rewetting process also releases physically protected SOM, increasing the amount of extractable SOM-C by up to 200%. The additional SOM-C rendered soluble by the rewetting event did not contribute substantially to the rewetting CO2 pulse. Overall, the rapid rewetting of a dry soil can influence soil C cycling in the short-term, by increasing the microbial mineralization of cytoplasmic solutes, and in the longer-term, by decreasing the total amount of SOM physically protected within microaggregates.