The preservation of the natural amenities within the planned unit development shall be given due consideration, which shall include topography, trees, ground cover, natural bodies of water, and other significant natural features. Existing trees shall be preserved wherever possible. The location of trees shall be considered when planning the common open space, location of buildings, underground services, walks, paved areas, playgrounds, parking areas, and finished grade levels. The Planning Commission shall inquire into the means whereby trees and other natural features will be protected during construction. Excessive site clearing of topsoil, trees and natural features before the commencement of building operations shall be discouraged by the Planning Commission.