| Summary: | 碩士 === 國立臺灣大學 === 生物環境系統工程學研究所 === 96 === The purpose of this study is to discuss the influences of the soil water content on earthworm movements. Three situations including earthworm movement in the soil with dry surface, and the movement of either healthy or sick earthworms in the soil during rainfall via numerical simulations were studied. This study was based upon two assumptions. First, the earthworms inhabit in the homogenous soil. Second, The earthworms go towards the soil with higher growth curve. Here, an 1-D earthworm movement-water content governing equation (EWE) was proposed to describe the relationship between earthworm movement and soil water content. The relationship between displacement of the earthworms and time, thus, was derived by integrating EWE with time. The simulation of the earthworm movement required with some experimental parameters, such as hydraulic conductivities, the theory maximum drilling velocity (TMDV) of the earthworm, etc. The simulation of earthworm movement was terminated once the earthworms reached the ground surface, since ultraviolet radiation can cause earthworms paralysis based upon the previous studies. The numerical simulation results match with the previous studies and show that (1) earthworms manage to move downwards to the soil as ground surface is drying, (2) earthworms tend to move to the surface under greater rainfall intensity, and (3) earthworms are more likely to move to the surface at rainfall while they are sick. All of the three conclusion match with the with former observations.
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