The unexplored role of preferential flow in soil carbon dynamics
The unexplored role of preferential flow in soil carbon dynamics
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DOI：
10.1016/j.soilbio.2021.108398
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发表时间：
2021-10
影响因子：
9.7
通讯作者：
Shane Franklin;A. Kravchenko;R. Vargas;B. Vasilas;J. Fuhrmann;Yan Jin
中科院分区：
文献类型：
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作者：
Shane Franklin;A. Kravchenko;R. Vargas;B. Vasilas;J. Fuhrmann;Yan Jin
水是控制土壤有机质归宿和处理的关键因素。水通常通过优先流动路径流过包气带，导致不均匀和快速渗透。因此，大部分土壤基质被绕过。优先流动路径通常与连接良好的大孔隙网络（>300 μm Ø）相关，在水的可用性、营养输送和排水后的再氧化之间提供独特的平衡。水分、营养物质和氧气浓度的提高使这些地方成为微生物活动的最佳场所。流动路径通常显示时间稳定性。这种稳定性导致随着时间的推移反复润湿和生物地球化学再活化，对与土壤中微生物功能和碳循环有关的微环境条件产生持久影响。尽管几十年的优先流的研究，仍然有必要连接流路和由此产生的异质水分分布土壤功能。在这篇综述中，我们讨论了如何优先流可以作为一个参考框架的空间和时间异质性土壤碳地球化学循环。我们强调结合目前的孔隙尺度碳动力学知识的重要性，赞赏连接网络的水力活性孔隙/土壤剖面内的路径。这种组合为扩大孔隙规模过程并纳入宏观规模的资源异质性开辟了新的可能性。在这个液压连接的框架内工作可以提供洞察力的热时刻，这是时间上孤立的大脉冲CO2再润湿或解冻事件后的机械表示。最后，我们提出了知识差距的建议，并强调迫切需要将土壤物理学与生物学联系起来，以机械地了解土壤功能。
Water is a crucial factor controlling the fate and processing of soil organics. Water commonly flows through the vadose zone via preferential flow pathways, resulting in nonuniform and rapid infiltration. Hence, a large portion of the soil matrix is bypassed. Preferential flow paths, often associated with well-connected macropore networks (>300 μm Ø), offer a unique balance between water availability, nutrient delivery, and re-oxygenation upon drainage. The heightened concentrations of moisture, nutrients, and oxygen make these locations optimal for high rates of microbial activity. Flow paths often display temporal stability. This stability results in repeated wetting and biogeochemical reactivation through time creating a lasting impact on micro-environmental conditions relevant to microbial functioning and carbon cycling in soil. Despite decades of research on preferential flow, there is still a need to link flow paths and the resultant heterogeneous moisture distributions to soil function. In this review, we discuss how preferential flow can serve as a framework of reference for the spatially and temporally heterogeneous biogeochemical cycling of soil carbon. We highlight the importance of combining current knowledge of pore-scale carbon dynamics with an appreciation of connected networks of hydraulically active pores/paths within the soil profile. Such combination opens new possibilities for upscaling pore-scale processes with the inclusion of resource heterogeneity at the macroscale. Working within this hydraulically connected framework can provide insight for the mechanistic representation of hot moments, which are temporally isolated large pulses of CO2after rewetting or thawing events. We conclude with suggestions on knowledge gaps and stress the critical need of linking soil physics with biology to mechanistically understand soil functions.