估计不同质地土壤水分特征曲线的分形方法

Fractal approach for estimating soil water retention curves of various textures

利用UNSODAV2 0数据库中的分析资料 ,根据Tyler和Wheatcraft提出的估计土壤水分特征曲线的分形方法 ,计算出了 5 2 6个土样共 10种不同质地土壤各自的平均分形维数 ,且分别与它们中的粉粒加粘粒含量以及VanGenuchten模型中的参数n值进行了回归 ,并把计算与实测的土壤水分特征曲线做了对比。结果表明 ,土壤的质地越细 ,分形维数越大 ;随着参数n值的增大 ,分形维数减小。对粗质的土壤来说 ,用Tyler和Wheatcraft方法估计的土壤水分特征曲线效果较好 ,而对细质地的土壤精度较差。

In this paper, the fractal approach suggested by Tyler and Wheatcraft was used to estimate soil water retention curves based on the data in UNSODA version 2 0. Totally 526 soil samples were analyzed. The average fractal dimensions for 10 types of textures were calculated with silt and clay content being regressed. The parameter n in van Genuchten retention model was also obtained. Results indicate that finer textured soils show larger fractal dimensions and soils with higher n values correspoed to smaller fractal dimensions. Comparisons were also made between simulated and measured water retentio curves. The simulated values for coarse textured soils by Tyler Wheatcraft model agree well with observations, while the match is poor for fine textured soils.