The pilot of a helicopter reported that, after performing a series of reconnaissance passes, followed by an out of ground effect hover power check, he decided to fly an approach to a mountain meadow. During the approach to landing, the pilot slowed the descent rate and realized the rotor rpm had decayed rapidly. The pilot lowered the collective and applied forward cyclic to increase airspeed to regain rotor rpm but was unable to recover. He then lowered the collective to enter an autorotation. Upon touchdown, the tail skid struck the ground, the helicopter pitched forward, and the main rotor impacted terrain. The helicopter sustained substantial damage to the tailboom and the horizontal and vertical stabilizers. The pilot reported no mechanical issues with the helicopter that would have precluded normal operations.