Roose T, Fowler A C
Mathematical Institute, Oxford University, 24-29 St Giles', Oxford OX1 3LB, UK.
J Theor Biol. 2004 May 21;228(2):155-71. doi: 10.1016/j.jtbi.2003.12.012.
We present a model for water uptake by plant roots from unsaturated soil. The model includes the simultaneous flow of water inside the root network and in the soil. It is constructed by considering first the water uptake by a single root, and then using the parameterized results thereby obtained to build a model for water uptake by the developing root network. We focus our model on annual plants, in particular the model will be applicable to commercial monocultures like maize, wheat, etc. The model is solved numerically, and the results are compared with approximate analytic solutions. The model predicts that as a result of water uptake by plant roots, dry and wet zones will develop in the soil. The wet zone is located near the surface of the soil and the depth of it is determined by a balance between rainfall and the rate of water uptake. The dry zone develops directly beneath the wet zone because the influence of the rainfall at the soil surface does not reach this region, due to the nonlinear nature of the water flow in the partially saturated soil. We develop approximate analytic expressions for the depth of the wet zone and discuss briefly its ecological significance for the plant. Using this model we also address the question of where water uptake sites are concentrated in the root system. The model indicates that the regions near the base of the root system (i.e. close to the ground surface) and near the root tips will take up more water than the middle region of the root system, again due to the highly nonlinear nature of water flow in the soil.
我们提出了一个关于植物根系从非饱和土壤中吸水的模型。该模型包括根系网络内部和土壤中水分的同时流动。它首先通过考虑单个根系的吸水情况构建，然后利用由此获得的参数化结果来建立发育中的根系网络的吸水模型。我们的模型主要针对一年生植物，尤其适用于玉米、小麦等商业单一栽培作物。该模型通过数值求解，并将结果与近似解析解进行比较。模型预测，由于植物根系吸水，土壤中会形成干区和湿区。湿区位于土壤表层附近，其深度由降雨和吸水速率之间的平衡决定。干区直接在湿区下方形成，这是因为由于部分饱和土壤中水流的非线性性质，土壤表面降雨的影响无法到达该区域。我们推导了湿区深度的近似解析表达式，并简要讨论了其对植物的生态意义。利用这个模型，我们还解决了根系中吸水部位集中在哪里的问题。模型表明，由于土壤中水流的高度非线性性质，根系基部附近（即靠近地面）和根尖附近的区域比根系中部吸收的水分更多。
