Response characteristics and tomographic monitoring of the electric capacitance after irrigation in the soil–plant (ginkgo tree) continuum in a laboratory

Abstract

The temporal and spatial variations of electrical capacitance of the soil–plant continuum in a laboratory were investigated. Based on a potted ginkgo tree with six irrigations, the electrical capacitance of the soil, trunk, and soil–trunk electrode pairs was measured, corresponding soil water content was computed, and spatial imaging was conducted. The soil electrical capacitance increases to a local maximum value immediately after irrigation, and then decreases gradually with time. During the late period of each drying procedure, there is a decussation area of high water content at the middle part of the circular region in the spatial imaging, which indicates root distribution in soil to some degree. Upon irrigation under a dry soil condition, the trunk electrical capacitance gradually increases for a period, and then begins to fluctuate with time; whereas, under a wet soil condition, it always fluctuates with time. Under a stable condition of overall change, the trunk electrical capacitance changes saltatorially and daily periodically. The temporal variation of the soil–trunk electrical capacitance exhibits both the character of soil and trunk.