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A Phytochorion, in phytogeography, is a geographic area with a relatively uniform composition of plant species. Adjacent phtyochoria do not usually have a sharp boundary, but rather a soft one, a transitional area in which many species from both regions overlap. The region of overlap is called a vegetation tension zone. ExplanationSeveral systems of classifying geographic areas where plants grow have been devised. Most systems are organized hierarchically, with the largest units subdivided into smaller geographic areas, which are made up of smaller floristic communities, and so on. phtyochoria are defined as areas possessing a large number of endemic taxons. Floristic kingdoms are characterized by a high degree of family endemism, floristic regions – by a high degree of generic endemism, floristic provinces – by a high degree of species endemism. Systems of phytochoria have both significant similarities and differences with zoogeographic provinces, which follow the composition of mammal families, and with biogeographical provinces or terrestrial ecoregions, which take into account both plant and animal species. The term phytochorion is especially associated with the classifications according to the methodology of Josias Braun-Blanquet , which is tied to the presence or absence of particular species.1 Taxonomic databases tend to be organized in ways which approximate floristic provinces, but which are more closely aligned to political boundaries, for example according to the World Geographical Scheme for Recording Plant Distributions. Floristic kingdomsBotanist Ronald Good identified six floristic kingdoms (Boreal, Neotropical, Paleotropical, South African, Australian, and Antarctic), the largest natural units he determined for flowering plants. Good's six kingdoms are subdivided into smaller units, called provinces. The Paleotropical kingdom is divided into three subkingdoms, which are each subdivided into floristic provinces. Each of the other five kingdoms are subdivided directly into provinces. There are a total of 37 floristic provinces. Almost all provinces are further subdivided into floristic regions. Armen Takhtajan, in a widely used scheme that builds on Good's work, identified thirty-five floristic regions, each of which is subdivided into floristic provinces, of which there are 152 in all. Takhtajan's floristic provinces
Holarctic KingdomI. Circumboreal Region
II. Eastern Asiatic Region
III. North American Atlantic Region
IV. Rocky Mountain Region
V. Macaronesian Region
VI. Mediterranean Region
VII. Saharo-Arabian Region
VIII. Irano-Turanian Region
IX. Madrean Region
Paleotropical KingdomX. Guineo-Congolian Region
XI. Usambara-Zululand Region
XII. Sudano-Zambezian Region
XIII. Karoo-Namib Region
XIV. St.Helena and Ascension Region
XV. Madagascan Region
XVI. Indian RegionXVII. Indochinese Region
XVIII. Malesian Region
XIX. Fijian Region
XX. Polynesian Region
XXI. Hawaiian Region
XXII. Neocaledonian Region
Neotropical KingdomXXIII. Caribbean Region
XXIV. Region of the Guayana Highlands
XXV. Amazonian RegionXXVI. Brazilian RegionXXVII. Andean Region
South African KingdomXXVIII. Cape Region
Australian KingdomXXIX. Northeast Australian Region
XXX. Southwest Australian RegionXXXI. Central Australian or Eremaean Region
Antarctic KingdomXXXII. Fernandezian Region
XXXIII. Chile-Patagonian Region
XXXIV. Region of the South Subantarctic IslandsXXXV. Neozeylandic Region
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