As a part of an estimation method of the heat storage rate within forest biomass, two simple schemes are presented for a calculation of the heat conduction into a cylindrical material. One is a modified version of the so-called Force-Restore method, and the other is a method based on the digital filter. Both methods are tested against analytical solutions of the heat-conduction equation for given diurnal cycles of the cylinder-surface temperature. The modified Force-Restore method gives acceptable results when the diurnal change in the surface temperature is not very different from a sinusoidal wave of 1-day cycle. The digital filter method can produce correct results for any patterns of diurnal cycles, if the time series of the surface temperature is given for more than 1-day period centered by the evaluation time of heat storage. Both method can be applied to an entire forest, if stems of the forest are classified into adequate classes in terms of their radii.
