An improved tree harvesting method is performed by a machine which includes a pair of booms mounted on a vehicle. A clamp assembly is mounted on a first boom for gripping a standing tree which is then severed close to the ground by a shear assembly which is also mounted on the first boom. The severed tree is positioned relative to a delimbing mechanism mounted on the second boom by moving the clamp assembly to place the tree in a generally horizontal position. The tree and clamp assembly are then pivoted about a longitudinal axis of the first boom to position the tree for engagement by the delimbing mechanism. The severed tree is delimbed by extending the second boom to move the delimbing mechanism along the trunk of the tree while the tree is gripped by the clamp assembly. When the delimbing mechanism senses or encounters a portion of the tree having a predetermined cross-sectional dimension, a topping assembly is automatically operated to top the tree by severing the tree trunk under the influence of movement of the topping assembly along the tree trunk. The log formed by delimbing and topping the severed tree is then deposited in a bunk assembly for transporting. The bunk assembly advantageously includes a support member or roller which is raised upon operation of the bunk assembly to an open condition to at least partially disengage logs from the bunk assembly.
