THE PRIVATE PILOT HAD LEVELED OFF AT 2,000 FEET MSL WHEN THE ENGINE GRADUALLY LOST POWER. HE TURNED BACK TOWARD THE AIRPORT, BUT WAS UNABLE TO MAINTAIN ALTITUDE. HE APPLIED CARBURETOR HEAT, AND THE ENGINE RESPONDED; HOWEVER, HE COULD NOT AVOID COLLIDING WITH A TALL TREE. THE AIRPLANE CRASHED INTO THE TOP OF THE TREE, AND THE PILOT EXITED THE AIRPLANE UNHURT. ACCORDING TO CARBURETOR ICING CHARTS, THE WEATHER CONDITIONS WERE CONDUCIVE TO THE FORMATION OF CARBURETOR ICE