Abstract: At the end of a crane arm on a base vehicle is fixed a frame, the inclination of which is controlled by double-acting hydraulic cylinders, and which supports hydraulically operated grip arms and a cutting unit. The frame is moved with an estimated inclination against a tree, and the grip arms urge the frame into conformance with the actual inclination of the tree, thereby inducing strains in the tree as well as the firmly based crane arm. A valve connecting the inlet and outlet of each hydraulic cylinder is momentarily opened from its hitherto closed position, so that the fluid in the cylinder is forced to equalize under the strains from the biased tree which consequently will be relieved from tension before cutting, otherwise resulting in cracks in the root end of the tree.