The pilot and two passengers were departing from a 2,800-ft-long turf runway and reported that prior to initiating the takeoff the wind was light and variable. During the initial climb after takeoff, and once the airplane had cleared a ridge and trees that ran parallel to the runway, the pilot reported that there was a “sudden windshear that caused a reduction in lift.” The pilot reduced the airplane’s pitch attitude in an attempt to regain lift, but the airplane continued to descend. The pilot was unable to arrest the descent and the airplane subsequently impacted the ground. The pilot reported that there were no mechanical malfunctions or failures of the airplane that would have precluded normal operation. The automated weather observation at an airport 9 miles away noted wind at 10 knots, with no gusts or other convective activity described.