The pilot was landing the Cessna 120, on a 2,000-foot-long, turf runway, at a private airport. While on the base leg of the traffic pattern, he applied carburetor heat and reduced the engine power to idle. The pilot reported that when he turned onto the final leg, the airplane was lower than he wanted it be and he advanced the throttle control; however, the engine did not respond. The airplane subsequently struck trees prior to the runway, and then impacted the ground. Both wings and the fuselage were substantially damaged. The National Transportation Safety Board was notified of the accident by the pilot, about 1 month after the accident. Examination of the airplane by a Federal Aviation Administration inspector was conducted about 6 weeks after the accident, and did not reveal evidence of any preaccident malfunctions. The weather reported at an airport located about 9 miles northeast of the accident site; about the time of the accident, included a temperature of 9 degrees Celsius C, and a dew point of -7 degrees C.