A landscaped buffer of not less than 20 feet in width shall be provided along any common property line in a side or rear yard. Buffers may be comprised of earth berms, fences and landscaping, which shall be of a sufficient quantity and size to screen parked automobiles from view of those at grade or first floor level in adjacent homes and to prevent the shining of automobile head lights into the yards of adjacent property. In general, this buffer shall provide a visual screen between the parking areas in the immediate vicinity of the residentially zoned property at an elevation of no less than seven feet above the finished grade of the parking areas. In addition, shade or ornamental trees shall be provided in the buffer at the rate of one per 1,000 square feet of buffer area.