"In addition to the incentives under this section, private landowners who engage in tree farming on areas fifty hectares or below by planting their lands with Ipil-Ipil and other fast-growing trees shall be exempt from the inventory requirement and other requirements before harvest as provided in this Decree for lessees of forest lands of the public domain: Provided, That the transport of trees cut shall be accompanied by the corresponding certificate of origin duly issued by the authorized forest officer."