Section 21.3 - Definitions(a)Public recreation area or recreation area means any land, title to which is in the United States and under the administration or jurisdiction of the Department of the Interior that is suitable for recreational purposes, including all such areas of the National Park System not excepted by § 21.2 , Bureau of Reclamation Reservoir areas, and any other areas dedicated to or administered by the Department for public recreational use.(b)Conservation area means any land, title to which is in the United States and under the administration or jurisdiction of the Department of the Interior that is designated for fish, wildlife, or other conservation purposes, including all such areas of the National Wildlife Refuge Systems, National Fish Hatchery Systems, and any other such areas administered by the U.S. Fish and Wildlife Service; also, land administered by the Bureau of Land Management and suitable for conservation or protection of fish or wildlife.(c)Permit means any lease, license, or other contract whereby a public recreation or conservation area is made available, in whole or part, to an individual or group for recreational purposes for a stipulated period of time, but does not include leases or transfers to other Federal or non-Federal public agencies.(d)Cabin site means any area within a public recreation or conservation area whose occupancy and use is granted to an individual or group for a period of time by permit.(e)Substantial improvement means any building, structure, or other relatively permanent facility or improvement affixed to a cabin site, utilized for human occupancy or related purposes, and costing or worth $1,000 or more. It does not include trailers or similar removable facilities.(f)Investment in a substantial improvement refers to the basic expenditure of moneys or property in kind in connection with a particular improvement. Thus, for example, where property is conveyed by testamentary or inter vivos gift, the donee will be seen only as occupying the position of the donor with respect to the time and amount of the investment since it was the donor who made the investment.(g)Amortization is the process whereby the investor in a substantial improvement derives sufficient use and/or economic benefit from the improvement over a period of time as to reasonably compensate for his investment.(h)Trespasser means any person who is occupying land in a public recreation or conservation area without a valid permit.(i)Authorized Officer means any person or persons designated by the head of any bureau or office of the Department with administrative jurisdiction over a particular conservation or recreation area, to make determinations and take other actions, consistent with the regulations in this part with respect to such area.