On October 4, 2007, about 1450 Alaska daylight time, a wheel-equipped Aviat A1B (Husky) airplane, N739, operated by the U.S. Department of the Interior as a public use training flight under Title 14, CFR Part 91, sustained substantial damage during an off-airport landing, about 17 miles southeast of Palmer, Alaska. The airline transport pilot/flight instructor and the commercial pilot/student were not injured. The local flight departed the Lake Hood airstrip, Anchorage, Alaska, about 1400. Visual meteorological conditions prevailed at the time of the accident, and a company VFR flight plan was in effect. According to interviews with air safety investigators for the operator, and the pilot's and operator's written statements, the purpose of the flight was for the pilot to evaluate and provide instruction to the commercial pilot on off-airport landings. During the accident landing, the flight instructor pilot, who was seated in the rear tandem seat, was demonstrating a touch and go landing to the commercial pilot when the left wing struck a clump of small trees/tall vegetation, and yawed to the left. The flight instructor was able to continue the touch and go, and successfully flew the airplane to Anchorage, where it was determined that the left wing required a rib to be replaced. The operator's aviation mechanics and air safety investigators, noted that there were no preaccident mechanical problems with the airplane.