To preserve, dry, fell and saw up a tree to be felled alone as a standing tree without adversely affecting the environment of forest or plantation.

An aqueous solution of a wood preserving agent containing borate as a primary effective ingredient is injected into the root of the tree and distributed throughout the tree by utilizing the conductive function of the tree. Then the ascent of water from the root is stopped to make the tree wither/dry, and then the tree is felled and sawed up.