A new concept for modelling the moisture dependence of heterotrophic soil respiration
A new concept for modelling the moisture dependence of heterotrophic soil respiration
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DOI：
10.1016/j.soilbio.2023.109147
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发表时间：
2023-08-16
影响因子：
9.7
通讯作者：
Zhang，Xiaoxian
中科院分区：
文献类型：
--
作者：
Huang，Zhongdong;Liu，Yuan;Zhang，Xiaoxian
异养土壤呼吸的水分依赖性是影响土壤有机碳(SOC)对全球变暖响应的不确定性的关键因素。考虑到非饱和土壤的异养呼吸主要是由微生物还原氧气(O2)驱动的，我们提出了一个新的概念，通过跟踪土壤孔隙中气体O2的溶解及其随后的扩散和微生物还原来模拟呼吸作用。土壤样本的总呼吸量是通过将土壤中所有微生物减少的O2相加而计算出来的。这使我们能够分离发生在微站点的物理过程和微生物活动，并将孔隙尺度底物的异质性、大孔隙和其他因素明确地纳入模型中。我们表明，在土壤样本上放大这些微观物理过程会使土壤水分、温度和其他因素内在地整合在它们对微生物呼吸的影响中，并且其中一个因素的变化会影响呼吸作用对另一个因素变化的反应。与实验数据的对比表明，该模型能较好地再现不同实验观测到的土壤水分-呼吸关系，并能预测土壤呼吸随温度的变化。值得注意的是，以前的研究将异养土壤呼吸的水分和温度敏感性的变化归因于微生物的适应；在这里，我们证明了土壤结构和物理过程的变化也可以引起这种变化。因此，在数据分析和建模中区分物理效应和微生物效应至关重要，因为将物理效应误认为微生物适应将导致错误地预测有机碳对环境变化的反应。
The moisture dependence of heterotrophic soil respiration is a key factor affecting the uncertainty in predicting the response of soil organic carbon (SOC) to global warming. Considering that heterotrophic respiration from unsaturated soils is primarily driven by microbial reduction of oxygen (O2), we propose a new concept to model the respiration by tracking dissolution of gaseous O2and its subsequent diffusion and microbial reduction at hydrated microsite in the pore space of soil. Total respiration from a soil sample is calculated by summing the O2reduced by all microbes in the soil. This allows us to separate physical processes and microbial activity occurring at microsites and incorporate pore-scale substrate heterogeneity, macropores and other factors explicitly into the model. We show that scaling up these microscopic physical processes over a soil sample makes soil moisture, temperature, and other factors inherently integrated in their influence on microbial respiration, and that a change in one of them affects the response of the respiration to the change in others. Comparison with experimental data shows the model can reproduce the diverse moisture-respiration relationships observed from various experiments and predict the change in soil respiration with temperature. It is noteworthy to point out that previous studies had attributed the variations in the moisture and temperature sensitivity of heterotrophic soil respiration to microbial adaptation; herein we demonstrate that changes in soil structure and physical processes can also give rise to such variations. Distinguishing between physical and microbial effects in data analysis and modelling is therefore crucial, as mistaking physical effects for microbial adaptation would lead to errors in predicting the response of SOC to environmental changes.