Modified conceptual model for compensated root water uptake – A simulation study
Modified conceptual model for compensated root water uptake – A simulation study
复制标题
DOI：
10.1016/j.jhydrol.2015.12.047
复制
发表时间：
2016-03
影响因子：
6.4
通讯作者：
A. Peters
中科院分区：
文献类型：
--
作者：
A. Peters
在宏观方法中模拟根系吸水通常是通过在理查兹方程中引入一个汇项来完成的。这个汇项表示潜在的吸水量减少了所谓的应力减少因子，解释了由于高吸力，缺氧或盐度造成的应力。由于土壤某些部分的应力可以通过应力较小部分的吸水增强来补偿，因此提出了几种补偿模型。其中之一是贾维斯的经验模型，由于其数学上的优雅和简单，经常被应用。然而，它已被讨论，在某些条件和假设下，该模型可能会预测过高的蒸腾速率，这是不符合假设的应力降低功能。本文的目的是（i）分析这些不一致和（ii）引入一个简单的限制蒸腾的方式，如果完整的水将采取形式的位置，在未补偿的情况下，最高的吸收率。从50厘米深的土壤与水力功能代表不同的质地，从粘壤土到粗砂，蒸腾模拟与原始和修改后的模型，使用HYDRUS-1D。假定根系分布均匀或随深度线性递减。在质地较好的土壤和均匀的根系密度的情况下，如果吸收的最大增强因子为2，则即使整个根域已经受到严重胁迫，原始模型预测的蒸腾等于潜在蒸腾。这些结果与应力折减函数的原意不符。修改消除了不一致的限制蒸腾作用的最大值的基础上，在根区的最高未补偿的吸收速率。它既不增加数学复杂性，也不需要任何额外的参数。
Modeling root water uptake within the macroscopic approach is usually done by introducing a sink term in the Richards equation. This sink term represents potential water uptake reduced by a so-called stress reduction factor accounting for stress due to high suctions, oxygen deficit or salinity. Since stress in some parts of the soil can be compensated by enhanced water uptake in less stressed parts, several compensation models have been suggested. One of them is the empirical model of Jarvis, which is often applied due to its mathematical elegance and simplicity. However, it has been discussed that under certain conditions and assumptions this model might predict too high transpiration rates, which are not in agreement with the assumed stress reduction function. The aim of this paper is (i) to analyze these inconsistencies and (ii) to introduce a simple constraint for transpiration in a way as if the complete water would be taken form the location with highest uptake rate in the uncompensated case. Transpiration from 50 cm deep soils with hydraulic functions representing different textures, ranging from a clay loam to a coarse sand, was simulated with the original and the modified model using HYDRUS-1D. Root distribution was assumed to be uniform or linearly decreasing with depth. In case of the fine textured soils and uniform root density, the original model predicted transpiration equal to potential transpiration even when the complete root domain was already heavily stressed if the maximum enhancement factor for uptake was 2. These results are not in agreement with the original meaning of the stress reduction function. The modification eliminates the inconsistencies by limiting transpiration to a maximum value based on the highest uncompensated uptake rate in the root zone. It does neither increase the mathematical complexity nor require any additional parameters.