An estimation method of ground resistance of trees growing in different lands

It is important to monitor the growing state of tree roots without digging the soil away from the bottom of the tree. Electrical ground resistance of tree roots indicates the grade of the growing state. The better roots advanced in the ground, the smaller the value of ground resistance becomes. However, ground resistance of the tree is modified by resistivity of the soil. If the growing state of roots is the same in trees growing in different lands, the value of ground resistance of each tree shows different values according to soil resistivity where trees are growing. This disables the comparison of the growth level between different lands, and complicates the estimation of results. In order to make comparison possible between the two without the effect of soil resistivity, the value of ground resistance of the tree is converted to that of a metal disk electrode. Here, if we know the soil resistivity, a radius of the disk becomes to be known. This disk radius is called equivalent radius that can indicate the growth level according to its value regardless of soil resistivity. Using the equivalent radius, we can estimate the growth level of plants growing in different lands evenly. Measured equivalent radii and the ratios to their butt radius of objective trees in West Australia, Hawaii Island, and Japan are summarized in figures.