In fact, our preliminary experiments confirmed a significant level of amylase activity in the sap. Thus, a part of the free sugar increase is attributed to the starch degradation. However, possible amount of glucose and fructose generated from starch is far small, compared to the sugar increase as calculated. This suggests that hydrolysis of cellulose and/or hemicellulose also occurs in the felled trunks to produce monosaccharides.