While on initial climb after takeoff the airplane encountered windshear and the airplane stalled, subsequently impacting the terrain. The pilot reported the takeoff and initial climb were normal until approximately 300 feet above ground level when the airplane encountered "severe turbulence, causing left turn and loss of lift." The pilot stated the engine was producing "full power" when the airplane impacted the terrain. The winds were 020 degrees magnetic at 12 knots, with gusts of 17 knots.