Abstract By creating vertical and continuous burrows, anecic earthworms accelerate the transfer of water in soils. However, the degradation mechanisms and lifespan of burrows and the consequence of changes in burrow characteristics for water infiltration remain poorly known. In this study, the dynamics of the degradation and hydraulic properties of burrows made by the anecic earthworm Amynthas khami in a clayey soil were investigated in a meadow and in a woodland in North Vietnam. We selected three categories of surface casts, namely, (i) fresh (a few days old), (ii) dry (>1 month old) and (iii) degraded by rain (older than the dry casts), as proxies of the age of burrows. The physical and chemical properties of casts were measured and compared to the surrounding soil aggregates without visible earthworm activity (control). Soil cores were sampled below casts and control and the 3D structure of burrows was characterized using X-ray tomography. Then, water infiltration was measured in the saturated soil cores. Fresh and degraded casts had a lower water stability than control aggregates, whereas higher values were found in dry casts. Water infiltration was twice higher in columns below fresh and dry casts than in the control. However, below degraded casts, the positive effect on water infiltration was reduced or disappeared in some cases. The degradation of burrows led to significant increase in the specific surface area, decrease in their minimum diameter and increase in the abundance of cracks connected to burrows. Our results indicate that anecic burrows persist at least for months below degraded casts but that aging due mainly to physical processes reduces water infiltration. This study highlights the importance of taking into account the lifetime of burrows in the soil when assessing the effect of earthworms on soil structure and water transfer.

中文翻译：

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年龄问题：由厌食的 Amynthas khami 产生的蚯蚓粪和洞穴的动态及其对土壤水分渗透的影响

摘要 通过创造垂直和连续的洞穴，厌食蚯蚓加速了土壤中水分的转移。然而，洞穴的降解机制和寿命以及洞穴特征变化对水渗透的影响仍然知之甚少。在这项研究中，在越南北部的草地和林地中，研究了在黏质土壤中由厌食蚯蚓 Amynthas khami 挖出的洞穴的降解和水力特性的动力学。我们选择了三类表面铸件，即（i）新鲜（几天大），（ii）干燥（> 1 个月大）和（iii）被雨降解（比干铸件更旧），作为洞穴的年龄。测量铸件的物理和化学特性，并与周围没有可见蚯蚓活动（对照）的土壤团聚体进行比较。在铸件和对照下方对土壤核心取样，并使用 X 射线断层扫描表征洞穴的 3D 结构。然后，在饱和土壤核心中测量水渗透。新鲜和降解的铸件的水稳定性低于对照骨料，而干铸件的水稳定性更高。新鲜和干燥铸件下方的柱子中的水渗透比对照高两倍。然而，在退化的铸件之下，在某些情况下对水渗透的积极影响减少或消失。洞穴的退化导致比表面积显着增加，其最小直径减小，与洞穴相连的裂缝数量增加。我们的研究结果表明，在退化的铸件之下，枯竭的洞穴至少会持续数月，但主要由于物理过程导致的老化减少了水的渗透。这项研究强调了在评估蚯蚓对土壤结构和水分转移的影响时考虑土壤中洞穴寿命的重要性。