The vast carbon sequestration potential of soil implies that even minor changes in its characteristics can impact atmospheric carbon levels. However, little research has focused on the influence of rainfall-induced physical crusts, a common natural phenomenon, on soil organic carbon (SOC). In this study, we simulated contour farming patterns and induced artificial rainfall to obtain different types of physical crusts (structural and depositional crusts). We determined their effects on SOC mineralization rates and distribution and utilized XCT scanning technology to gather surface pore data, attempting to explain the reasons from the perspective of pore structure changes. The formation of physical crusts significantly enhanced SOC mineralization. During the 27-day mineralization experiment, the production of structural and depositional crusts increased cumulative mineralization rates by at least 23.07 % and 18.57 %, respectively. The underlying cause of this phenomenon is closely related to the drastic changes in soil pore structure, particularly the increase in the proportion of micropores and the enhancement of pore connectivity after crust cracking. Additionally, rainfall resulted in SOC enrichment in the surface crust but led to increased participation of subsoil organic carbon in the mineralization process. Consequently, the level of SOC in subsoil significantly decreased after the formation of physical crusts compared to soil without crusts. This study reveals the impact of rainfall-induced soil physical crusts on SOC release and storage and provides a microscopic pore perspective to explain the underlying mechanisms. Against the backdrop of global climate change, this research supplements theoretical understanding of the effects of rainfall events on soil carbon pools and predictions of soil organic carbon release.

中文翻译：

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降雨诱发的物理结皮通过表面孔隙结构对土壤碳分布和矿化的影响


土壤的巨大固碳潜力意味着，即使其特性的微小变化也会影响大气中的碳水平。然而，很少有研究关注降雨引起的物理结皮（一种常见的自然现象）对土壤有机碳 （SOC） 的影响。在这项研究中，我们模拟了等高耕作模式并诱导人工降雨，以获得不同类型的物理结皮 （构造和沉积结壳）。本文确定了它们对土壤有机碳矿化速率和分布的影响，并利用XCT扫描技术收集表面孔隙数据，试图从孔隙结构变化的角度解释其原因。物理结壳的形成显著增强了 SOC 矿化。在 27 天的矿化实验中，构造和沉积地壳的产生分别使累积矿化速率至少增加了 23.07% 和 18.57%。造成这种现象的根本原因与土体孔隙结构的剧烈变化密切相关，特别是结皮开裂后微孔隙比例的增加和孔隙连通性的增强。此外，降雨导致地表壳中的 SOC 富集，但导致底土有机碳在矿化过程中的参与增加。因此，与无结皮的土壤相比，物理结皮形成后底土中的 SOC 水平显著降低。本研究揭示了降雨引起的土壤物理结皮对 SOC 释放和储存的影响，并提供了微观孔隙视角来解释其潜在机制。 在全球气候变化的背景下，本研究补充了对降雨事件对土壤碳库影响和土壤有机碳释放预测的理论理解。