Quantifying heterogeneity of soil organic matter dynamics using radiocarbon

全球变暖加速了土壤有机质的微生物分解，增加了土壤向大气释放CO_2的速度；然而，由于缺乏关于SOM生物可降解性异质性的定量数据，这种影响的大小和时间仍然高度不确定。我们开发了一种定量了解SOM异质性的方法，该方法涉及将土壤样品化学分离成SOM组分，根据放射性碳同位素测量估计其平均停留时间（MRTs），并使用这些数据构建一个模型，将土壤表示为具有不同MRT范围的SOM池的复合体。基于对土壤有机质异质性的定量理解，我们的预测表明，在未来的一个世纪里，气候变暖将继续加速土壤碳从慢循环碳库中流失，其MRTs为20-200年。

Global warming can lead to accelerated microbial decomposition of soil organic matter (SOM) and enhance the release of CO_2 from the soil to the atmosphere ; however, the magnitude and timing of this effect remain highly uncertain due to a lack of quantitative data concerning the heterogeneity of SOM biodegradability. We developed a method to quantitatively understand the SOM heterogeneity, which involved chemically-separating soil samples into SOM fractions, estimating their mean residence times (MRTs) based on radiocarbon isotope measurements, and using the data to construct a model representing the soil as a complex of SOM pools with different MRT ranges. Our prediction based on the quantitative understanding of the SOM heterogeneity demonstrated that warming can continue to accelerate soil carbon loss from slow-cycling carbon pools with MRTs of 20-200 years over the next century.