Soil aeration is a critical factor for oxygen-limited subsoil processes, as transport by diffusion and advection is restricted by the long distance to the free atmosphere. Oxygen transport into the soil matrix is highly dependent on its connectivity to larger pore channels like earthworm and root colonised biopores. Here we hypothesize that the soil matrix around biopores represents different connectivity depending on biopore genesis and actual coloniser. We analysed the soil pore system of undisturbed soil core samples around biopores generated or colonised by roots and earthworms and compared them with the pore system of soil, not in the immediacy of a biopore. Oxygen partial pressure profiles and gas relative diffusion was measured in the rhizosphere and drilosphere from the biopore wall into the bulk soil with microelectrodes. The measurements were linked with structural features such as porosity and connectivity obtained from X-ray tomography and image analysis. Aeration was enhanced in the soil matrix surrounding biopores in comparison to the bulk soil, shown by higher oxygen concentrations and higher relative diffusion coefficients. Biopores colonised by roots presented more connected lateral pores than earthworm colonised ones, which resulted in enhanced aeration of the rhizosphere compared to the drilosphere. This has influenced biotic processes (microbial turnover/mineralization or root respiration) at biopore interfaces and highlights the importance of microstructural features for soil processes and their dependency on the biopore's coloniser.

中文翻译：

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根际和土层的毫米级曝气

土壤曝气是限氧底土过程的关键因素，因为通过扩散和平流的运输受到与自由大气的长距离限制。氧气输送到土壤基质中高度依赖于它与更大的孔隙通道（如蚯蚓和根定植生物孔）的连通性。在这里，我们假设生物孔周围的土壤基质代表不同的连通性，这取决于生物孔的发生和实际的殖民者。我们分析了由根和蚯蚓产生或定殖的生物孔周围未受干扰的土壤核心样品的土壤孔隙系统，并将它们与土壤的孔隙系统进行比较，而不是直接在生物孔中进行比较。用微电极测量从生物孔壁到大块土壤的根际和土壤中的氧分压分布和气体相对扩散。测量结果与从 X 射线断层扫描和图像分析获得的孔隙度和连通性等结构特征相关联。与大块土壤相比，生物孔周围的土壤基质中的通气增强，表现为较高的氧浓度和较高的相对扩散系数。与蚯蚓定殖的生物孔相比，由根定殖的生物孔呈现出更多连接的侧孔，这导致与根际相比，根际的通气增强。这影响了生物孔界面的生物过程（微生物周转/矿化或根系呼吸），并突出了土壤过程的微观结构特征及其对生物孔定殖者的依赖性的重要性。