作物根系影响下的农田干缩裂隙网络多重分形分析

【目的】分析农田中作物根系对土壤裂隙网络的影响。【方法】通过室外农田土壤裂隙试验,获得土壤裂隙数字图像,利用数字图像处理技术与编程计算,对比分析作物根系影响产生的裂隙网络与无根系影响的裂隙网络的广义分形维数D_q,多重分形奇异指数α以及分形谱函数f(α)。【结果】无作物的裂隙图像的面积密度大于含有作物的裂隙图像的面积密度,表明无作物的土壤裂隙宽度较大;无作物的土壤裂隙图像的长度密度与欧拉数均大于有作物根系的土壤裂隙图像,表明无作物根系的土壤裂隙较长且形成封闭的裂隙网络较多;广义分形维数的整体变化幅度为无作物裂隙大于有作物影响的裂隙;有作物根系影响的裂隙的谱宽小于无作物根系的土壤裂隙的谱宽;作物根系影响下的裂隙D_0值大于无作物的土壤产生的裂隙;根系影响下的土壤裂隙D_1更大;无作物土壤产生的裂隙的D_0与D_2的差值最小,说明其分布的非均匀性更好。【结论】作物根系的锚固作用并没有使土壤裂隙失去非均匀分布特性,土壤裂隙网络非均匀性特征明显;根系的影响使得土壤裂隙分布的非均匀性更小;测量尺度为25/8～50 cm时,无作物的裂隙分形复杂性最大。多重分形参数可以作对比作物影响下的裂隙与无作物的裂隙非均匀性的重要指标。

Multifractal Analysis of Shrinkage and Fracture in Farmland Under the Influence of Crop Root System

【Objective】The objective is to analyze the effect of crop root system on soil fissure network in farmland.【Method】Soil fissure digital image was obtained through outdoor soil fissure experiment.Generalized fractal dimension D_q, multifractal singular exponent α and fractal spectrum function f(α) were calculated and analyzed by using digital image processing technology and programming.【Result】The area density of crop-free fissure image was larger than that of the image containing crop, which indicated that the width of soil fissure without crop was larger. The length density and euler number of the images of soil fissures without crop roots were larger than those of soil fissures with crop roots, indicating that the soil fissures without crop roots were longer and more closed networks were formed. The overall variation range of the generalized fractal dimension was that the spectral width of the cracks without crop roots was larger than that of the cracks with crop roots, and the spectral width of the cracks with crop roots was smaller than that of the cracks without crop roots. Under the influence of crop root system, the crack D_0 value was greater than that of crop-free soil. Under the influence of root system,soil crack D_1 was larger. The difference between D_0 and D_2 was the smallest in the cranny produced by crop-free soil, indicating that the distribution was better non-uniform.【Conclusion】The anchoring action of crop root system did not make soil fissure lose its non-uniform distribution characteristic, and the non-uniform distribution of soil fissures network was obvious. Under the influence of root system, the heterogeneity of soil fissure distribution is smaller; When the measurement scale is 25/8～50 cm, the fractal structure of crop-free fissures is more complex. Multi-fractal parameters can be used as an important indicator to compare the non-uniformity of cracks and crop-free fractures under the influence of crops.