Quantitative aspects of heterogeneity in soil organic matter dynamics in a cool-temperate Japanese beech forest: a radiocarbon-based approach
Quantitative aspects of heterogeneity in soil organic matter dynamics in a cool-temperate Japanese beech forest: a radiocarbon-based approach
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DOI：
10.1111/j.1365-2486.2008.01745.x
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发表时间：
2009-03-01
影响因子：
11.6
通讯作者：
Hirai, Keizo
中科院分区：
文献类型：
--
作者：
Koarashi, Jun;Atarashi-Andoh, Mariko;Hirai, Keizo
土壤是陆地生态系统中最大的碳库;它储存的碳是大气的两倍。全球变暖会加速土壤有机碳（SOC）的微生物分解，增加土壤中CO2向大气的释放，但由于缺乏SOC生物降解性异质性的定量数据，这种影响的程度和时间仍高度不确定。因此，我们试图确定SOC池相对于其特定的平均停留时间（MRT），使用这些SOC池划分土壤呼吸源，并估计池的潜在响应变暖。我们收集了来自日本冷温带落叶林的表层土壤和凋落物样品，将样品化学分离成SOC组分，基于放射性碳（C-14）同位素测量估计其MRT，并使用这些数据构建一个模型，将土壤表示为具有不同MRT范围的六个SOC池的复合体。我们估计，一个小的，快速循环的SOC池，MRT小于10年（对应于O层和可识别的植物叶片碎片在A1层）是负责73%的年度异养呼吸和44%的总土壤呼吸。然而，这些池对变暖的预测响应表明，由于基质可用性有限，快速循环SOC池的SOC损失率迅速减少（几十年内）。相反，在下一个世纪，变暖将继续加速慢循环池的SOC损失，MRT为20-200年。虽然使用C-14为基础的方法有缺点，这些估计提供了定量的见解的潜在重要性的慢循环SOC动态预测的正反馈气候变化。
Soil is the largest carbon reservoir in terrestrial ecosystems; it stores twice as much carbon as the atmosphere. It is well documented that global warming can lead to accelerated microbial decomposition of soil organic carbon (SOC) and enhance the release of CO2 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 SOC biodegradability. Therefore, we sought to identify SOC pools with respect to their specific mean residence times (MRTs), to use those SOC pools to partition soil respiration sources, and to estimate the potential response of the pools to warming. We collected surface soil and litter samples from a cool-temperate deciduous forest in Japan, chemically separated the samples into SOC fractions, estimated their MRTs based on radiocarbon (C-14) isotope measurements, and used the data to construct a model representing the soil as a complex of six SOC pools with different MRT ranges. We estimate that a minor, fast-cycling SOC pool with an MRT of less than 10 years (corresponding to the O horizon and recognizable plant leaf fragments in the A1 horizon) is responsible for 73% of annual heterotrophic respiration and 44% of total soil respiration. However, the predicted response of these pools to warming demonstrates that the rate of SOC loss from the fast-cycling SOC pool diminishes quickly (within several decades) because of limited substrate availability. In contrast, warming will continue to accelerate SOC loss from slow-cycling pools with MRTs of 20-200 years over the next century. Although using a C-14-based approach has drawbacks, these estimates provide quantitative insights into the potential importance of slow-cycling SOC dynamics for the prediction of positive feedback to climate change.