The pilot reported that after a normal landing onto a dirt road, which was covered with loose dirt and gravel, the airplane's right wing collided with a tree. The airplane rotated to the right approximately 20 degrees and began skidding sideways. He attempted to correct with rudder and brakes but the airplane exited the road and subsequently nosed over. According to the pilot, clear skies and a light breeze prevailed at the time of the accident. The pilot reported that there were no preimpact mechanical malfunctions or failures of the airframe or engine that would have precluded normal flight.