基于探地雷达的根系探测对土壤含水量的响应

在探地雷达对地下根系进行探测和识别的过程中,土壤含水量是影响根系探测效果的一个极为重要的因素。本文在2种质地土壤(砂质壤土和粘土)不同水分含量下,通过探地雷达对根进行模拟试验,测定了2种质地土壤的电磁波波速,同时测试了根的探测效果。结果表明:土壤含水量是影响电磁波波速的主要因素,电磁波波速不受天线频率的影响,但随着土壤含水量的增大而减小。本研究建立了2种质地土壤的电磁波波速(ν)与土壤含水量(θ)的理论模型,经过验证:发现该模型测算的根深度可以用来评估根的实际深度;在2种质地土壤中,根的分辨率均表现为随土壤水分含量增大而减弱,2者差异较大;当含水量>20.33%(砂质壤土)或>26.82%(粘土)时,均不适宜利用GPR进行根探测。

Response of root detection to soil moisture content based on ground penetrating radar

Soil water content is an important factor in the process of detecting and recognizing underground roots by ground penetrating radar(GPR).In this paper,the simulation test was conducted by using ground penetrating radar to detect the root under different water content in two kinds of soil(sandy loam and clay).The electromagnetic wave velocities of two soils with different water content were measured,and the detection effect of root by GPR was tested.The results showed that the soil moisture content was the main factor affecting the electromagnetic wave velocity.The electromagnetic wave velocity was not affected by the antenna frequency,but decreased with the increase of soil moisture content.The study established theoretical models of cubic polynomial relationship between velocity of electromagnetic wave(ν)and water content(θ)of two kinds of soil.It was found that the root depth estimated by the theoretical models could be used to evaluate the actual root depth.Meanwhile,the root resolution of GPR imaging diagram decreased with the increase of soil water content in both soils.However,there was a quite difference between the two soils.When the water content is higher than 20.33% for sandy loam or higher than 26.82% for clay,it is not suitable to use GPR for root detection.