<P> The term "Siberia" has a long history . Its meaning has gradually changed during ages . Historically, Siberia was defined as the whole part of Russia to the east of Ural Mountains, including the Russian Far East . According to this definition, Siberia extended eastward from the Ural Mountains to the Pacific coast, and southward from the Arctic Ocean to the border of Russian Central Asia and the national borders of both Mongolia and China . </P> <P> Soviet - era sources (Great Soviet Encyclopedia and others) and modern Russian ones usually define Siberia as a region extending eastward from the Ural Mountains to the watershed between Pacific and Arctic drainage basins, and southward from the Arctic Ocean to the hills of north - central Kazakhstan and the national borders of both Mongolia and China . By this definition, Siberia includes the federal subjects of the Siberian Federal District, and some of the Ural Federal District, as well as Sakha (Yakutia) Republic, which is a part of the Far Eastern Federal District . Geographically, this definition includes subdivisions of several other subjects of Urals and Far Eastern federal districts, but they are not included administratively . This definition excludes Sverdlovsk Oblast and Chelyabinsk Oblast, both of which are included in some wider definitions of Siberia . </P> <P> Other sources may use either a somewhat wider definition that states the Pacific coast, not the watershed, is the eastern boundary (thus including the whole Russian Far East) or a somewhat narrower one that limits Siberia to the Siberian Federal District (thus excluding all subjects of other districts). In Russian, the word for Siberia is used as a substitute for the name of the federal district by those who live in the district itself and less commonly used to denote the federal district by people residing outside of it . </P> <Table> Federal subjects of Siberia (GSE) <Tr> <Th> Subject </Th> <Th> Administrative center </Th> </Tr> <Tr> <Td_colspan="2"> Ural Federal District </Td> </Tr> <Tr> <Td> Khanty--Mansi Autonomous Okrug </Td> <Td> Khanty - Mansiysk </Td> </Tr> <Tr> <Td> Kurgan Oblast </Td> <Td> Kurgan </Td> </Tr> <Tr> <Td> Tyumen Oblast </Td> <Td> Tyumen </Td> </Tr> <Tr> <Td> Yamalo - Nenets Autonomous Okrug </Td> <Td> Salekhard </Td> </Tr> <Tr> <Td_colspan="2"> Siberian Federal District </Td> </Tr> <Tr> <Td> Altai Krai </Td> <Td> Barnaul </Td> </Tr> <Tr> <Td> Altai Republic </Td> <Td> Gorno - Altaysk </Td> </Tr> <Tr> <Td> Buryat Republic </Td> <Td> Ulan - Ude </Td> </Tr> <Tr> <Td> Irkutsk Oblast </Td> <Td> Irkutsk </Td> </Tr> <Tr> <Td> Republic of Khakassia </Td> <Td> Abakan </Td> </Tr> <Tr> <Td> Kemerovo Oblast </Td> <Td> Kemerovo </Td> </Tr> <Tr> <Td> Krasnoyarsk Krai </Td> <Td> Krasnoyarsk </Td> </Tr> <Tr> <Td> Novosibirsk Oblast </Td> <Td> Novosibirsk </Td> </Tr> <Tr> <Td> Omsk Oblast </Td> <Td> Omsk </Td> </Tr> <Tr> <Td> Tomsk Oblast </Td> <Td> Tomsk </Td> </Tr> <Tr> <Td> Tuva Republic </Td> <Td> Kyzyl </Td> </Tr> <Tr> <Td> Zabaykalsky Krai </Td> <Td> Chita </Td> </Tr> <Tr> <Td_colspan="2"> Far Eastern Federal District </Td> </Tr> <Tr> <Td> Sakha (Yakutia) Republic </Td> <Td> Yakutsk </Td> </Tr> </Table>

What percentage of the land in central siberia is considered permafrost