Estimation of root water uptake parameters by inverse modeling with soil water content data
Estimation of root water uptake parameters by inverse modeling with soil water content data
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DOI：
10.1029/2003wr002046
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发表时间：
2003-11
影响因子：
5.4
通讯作者：
F. Hupet;S. Lambot;R. Feddes;J. V. van Dam;M. Vanclooster
中科院分区：
文献类型：
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作者：
F. Hupet;S. Lambot;R. Feddes;J. V. van Dam;M. Vanclooster
在本文中，我们已经测试了逆建模方法的可行性，以获得根吸水参数（RWUP）从土壤含水量数据使用数值实验为三种不同质地的土壤和最佳干燥期。感兴趣的RWUP是生根深度和底部根长密度。在第一步中，进行了全面的敏感性分析。这表明，土壤含水量动态是相对不敏感的RWUP和敏感性取决于所考虑的土壤质地。对于中细质地土壤，由于相对较高的非饱和导水率值，敏感性特别低。这些允许发生“补偿效应”，即，垂直非饱和水通量在某种程度上掩盖了根系吸水。在第二步中，我们分析了仅优化RWUP时解的适定性（稳定性和非唯一性）。在这种情况下，除了粗糙和极细质地土壤的生根深度参数估计外，反问题显然是不适定的。在第三步中，我们解决了RWUP与系统的附加参数同时估计的情况（即，土壤水力参数）。对于这种情况，我们的研究表明，逆问题对于粗糙和非常细的质地土壤是适定的，如果使用强大的全局优化算法，则可以估计两个感兴趣的RWUP。相反，由于垂直非饱和水流的“补偿效应”，RWUP的估计对于中细质地土壤是不可行的。总之，我们可以说，逆建模方法可以应用于推导RWUP的一些土壤（粗糙和非常精细的质地），并大大提高了可行性，如果RWUP同时优化与其他参数。然而，需要进行更详细的研究，将逆建模方法应用于真实的情况下，可能会遇到其他问题，如土壤异质性和根系动态。
In this paper we have tested the feasibility of the inverse modeling approach to derive root water uptake parameters (RWUP) from soil water content data using numerical experiments for three differently textured soils and for an optimal drying period. The RWUP of interest are the rooting depth and the bottom root length density. In a first step, a thorough sensitivity analysis was performed. This showed that soil water content dynamics is relatively insensitive to RWUP and that the sensitivity depends on the texture of the considered soil. For medium‐fine textured soil, the sensitivity is particularly low due to relatively high unsaturated hydraulic conductivity values. These ones allow a “compensating effect” to occur, i.e., vertical unsaturated water fluxes overshadowing in some way the root water uptake. In a second step, we analyzed the well‐posedness of the solution (stability and nonuniqueness) when only RWUP are optimized. For this case, the inverse problem is clearly ill‐posed except for the estimation of the rooting depth parameter for coarse and the very fine textured soils. In a third step, we addressed the case where RWUP are estimated simultaneously with additional parameters of the system (i.e., with soil hydraulic parameters). For this case, our study showed that the inverse problem is well‐posed for the coarse and very fine textured soils, allowing for the estimation of both RWUP of interest provided that a powerful global optimization algorithm is used. On the contrary, the estimation of RWUP is unfeasible for medium‐fine textured soil due to the “compensating effect” of the vertical unsaturated water flows. In conclusion, we can state that the inverse modeling approach can be applied to derive RWUP for some soils (coarse and very fine textured) and that the feasibility is strongly improved if the RWUP are simultaneously optimized with additional parameters. Nevertheless, more detailed research is needed to apply the inverse modeling approach to real cases for which additional issues are likely to be encountered such as soil heterogeneity and root dynamics.