Rothamsted Repository Download
Rothamsted Repository Download
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根在生长过程中自然地施加轴向和径向压力，改变了根-土壤界面上土壤的结构排列。然而，经验模型表明，土壤致密化会对水分和养分的吸收产生负面影响，它发生在紧邻根表面，距离根的距离越小。在这里，我们使用非侵入性成像技术，在空间上绘制出根部周围土壤的结构梯度图，以确定根部生长在土壤结构形成的早期阶段中的作用。X射线计算机断层扫描不仅提供了一种原位和三维可视化根系的方法，而且还提供了一种方法，可以评估在接近和远离根-土壤界面的选定距离处，由根引起的土壤结构的精确变化。我们在空间上量化了三种常见但截然不同的植物(豌豆、番茄和小麦)在不同土壤质地和压实处理下产生的土壤结构变化。在三种植物类型中，在粘壤土和壤质沙土中都发现直接根面的孔隙度显著增加，而不是土壤致密化，目前认为是正常的。根据土壤质地和植物类型的不同，在距根部一定距离处记录了土壤的致密化。根凸壳的土壤质地×容重×植物种类间存在显著的互作，这表明豌豆和小麦在高容重的粘性土壤中生长得更好，而番茄则更喜欢容重较低的土壤。这些结果仅由高分辨率非破坏性图像揭示，表明尽管根渗透机制可导致土壤致密化(这可能对生长产生负面影响)，但直接根-土壤界面实际上是一个高孔隙度区域，这对发生在这种尺度上的几个关键的根际过程非常重要，包括水分和养分吸收以及气体扩散。
Roots naturally exert axial and radial pressures during growth, which alter the structural arrangement of soil at the root – soil interface. However, empirical models sug-gest soil densification, which can have negative impacts on water and nutrient uptake, occurs at the immediate root surface with decreasing distance from the root. Here, we spatially map structural gradients in the soil surrounding roots using non ‐ invasive imaging, to ascertain the role of root growth in early stage formation of soil structure. X ‐ ray computed tomography provided a means not only to visualize a root system in situ and in 3 ‐ D but also to assess the precise root ‐ induced alterations to soil structure close to, and at selected distances away from the root – soil interface. We spatially quantified the changes in soil structure generated by three common but contrasting plant species (pea, tomato, and wheat) under different soil texture and compaction treatments. Across the three plant types, significant increases in porosity at the immediate root surface were found in both clay loam and loamy sand soils and not soil densification, the currently assumed norm. Densification of the soil was recorded, at some distance away from the root, dependent on soil texture and plant type. There was a significant soil texture × bulk density × plant species interaction for the root convex hull, a measure of the extent to which root systems explore the soil, which suggested pea and wheat grew better in the clay soil when at a high bulk density, compared with tomato, which preferred lower bulk density soils. These results, only revealed by high resolution non ‐ destructive imagery, show that although the root penetration mechanisms can lead to soil densification (which could have a negative impact on growth), the immediate root – soil interface is actually a zone of high porosity, which is very important for several key rhizosphere processes occurring at this scale including water and nutrient uptake and gaseous diffusion.