After removing the floats from the Cessna 172M, the pilot taxied from the north end of the grass runway to the south end, to conduct a brake test confirming the brakes were operational. He then back-taxied the airplane to the north end of the approximate 1,200-foot-long, 75-foot-wide runway. During the taxi, the pilot noticed the grass runway was wet and rougher than expected, and conducted a high-speed taxi test prior to takeoff, to determine handling capability. The pilot conducted a short-field takeoff and the airplane accelerated normally. As the airplane crossed over a high spot, created by a culvert under the runway, the airplane began sliding on the grass towards the left side of the runway. The pilot applied more right aileron, then rudder, and then some right brake. At this point, the pilot decided to abort the takeoff. He brought the throttle to idle, applied the brakes, and shut off the magnetos. As the airplane slowed, the left wing contacted a tree, which pivoted the nose of the airplane into brush as it came to a stop approximately 600 feet beyond the north end of the runway. The left wing sustained substantial damage upon impact with the tree.