Brimhall G H, Chadwick O A, Lewis C J, Compston W, Williams I S, Danti K J, Dietrich W E, Power M E, Hendricks D, Bratt J
Science. 1992 Feb 7;255(5045):695-702. doi: 10.1126/science.255.5045.695.
Soils are differentiated vertically by coupled chemical, mechanical, and biological transport processes. Soil properties vary with depth, depending on the subsurface stresses, the extent of mixing, and the balance between mass removal in solution or suspension and mass accumulation near the surface. Channels left by decayed roots and burrowing animals allow organic and inorganic detritus and precipitates to move through the soil from above. Accumulation occurs at depths where small pores restrict further passage. Consecutive phases of translocation and root growth stir the soil; these processes constitute an invasive dilatational process that leads to positive cumulative strains. In contrast, below the depth of root penetration and mass additions, mineral dissolution by descending organic acids leads to internal collapse under overburden load. This softened and condensed precursor horizon is transformed into soil by biological activity, which stirs and expands the evolving residuum by invasion by roots and macropore networks that allows mixing of materials from above.
土壤通过化学、机械和生物耦合传输过程在垂直方向上形成差异。土壤性质随深度而变化，这取决于地下应力、混合程度以及溶解或悬浮状态下的物质移除与地表附近物质积累之间的平衡。腐烂的根系和穴居动物留下的通道使得有机和无机碎屑及沉淀物从上方穿过土壤。在小孔隙限制进一步通行的深度处会发生积累。物质转移和根系生长的连续阶段搅动土壤；这些过程构成了一个侵入性膨胀过程，导致正的累积应变。相比之下，在根系穿透深度和物质添加深度以下，下降的有机酸导致矿物溶解，从而在覆盖层负荷下引起内部塌陷。这个软化和压缩的前体层通过生物活动转化为土壤，生物活动通过根系和大孔隙网络的侵入搅动并扩展不断演化的残余物，使得上方的物质得以混合。
