The pilot stated the engine sputtered and quit while descending through 2,000 feet agl for approach to land. He was not using carburetor heat and had reduced the engine to 2,100 rpm. While landing in a field the aircraft struck trees. After the accident, usable fuel was found in each fuel tank and there was no contamination in the fuel. The engine was started and operated normally. The carburetor heat operated normally. Icing probability curves show the aircraft was operating in conditions conducive to serious icing at glide power and visible icing at glide and cruise power.