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Phytochorion

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Phytochorion

A phytochorion, in phytogeography, is a geographic area with a relatively uniform composition of plant species. Adjacent phytochoria 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.

Contents

In traditional schemes, areas in phytogeography are classified hierarchically, according to the presence of endemic families, genera or species, e.g., in floral (or floristic, phytogeographic) zones and regions, or also in kingdoms, regions and provinces, sometimes including the categories empire and domain. However, some authors prefer not to rank areas, referring to them simply as "areas", "regions" (in a non hierarchical sense) or "phytochoria".

Systems used to classify vegetation can be divided in two major groups: those that use physiognomic-environmental parameters and characteristics and those that are based on floristic (i.e. shared genera and species) relationships. Phytochoria are defined by their plant taxonomic composition, while other schemes of regionalization (e.g., vegetation type, physiognomy, plant formations, biomes) may variably take in account, according to the author, the apparent characteristics of a community (the dominant life-form), environment characteristics, the fauna associated, anthropic factors or political-conservationist issues.

Explanation

Several 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. Phytochoria 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, and 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" (Werger & van Gils, 1976) 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, mainly in Africa.

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.

Early schemes

In the late 19th century, Adolf Engler (1844-1930) was the first to make a world map with the limits of distribution of floras, with four major floral regions (realms). His Syllabus der Pflanzenfamilien, from the third edition (1903) onwards, also included a sketch of the division of the earth into floral regions.

Other important early works on floristics includes Augustin de Candolle (1820), Schouw (1823),Alphonse de Candolle (1855), Drude (1890) and Diels (1908).

Good (1947) regionalization

Botanist Ronald Good (1947) identified six floristic kingdoms (Boreal or Holarctic, 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.

Takhtajan (1978, 1986) regionalization

Armen Takhtajan (1978, 1986), 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.

I. Circumboreal region

1 Arctic province2 Atlantic Europe province3 Central Europe province4 Illyria or Balkan province5 Pontus Euxinus province6 Caucasus province7 Eastern Europe province8 Northern Europe province9 Western Siberia province10 Altai-Sayan province11 Central Siberia province12 Transbaikalia province13 Northeastern Siberia province14 Okhotsk-Kamchatka province15 Canada incl. Great Lakes province

II. Eastern Asiatic region

16 Manchuria province17 Sakhalin-Hokkaidō province18 Japan-Korea province19 Volcano-Bonin province20 Ryūkyū or Tokara-Okinawa province21 Taiwan province22 Northern China province23 Central China province24 Southeastern China province25 Sikang-Yuennan province26 Northern Burma province27 Eastern Himalaya province28 Khasi-Manipur province

III. North American Atlantic Region

29 Appalachian province (forested areas extending east to include the piedmont and west to the start of the prairies)30 Atlantic and Gulf Coastal Plain province31 North American Prairies province

IV. Rocky Mountain Floristic Region

32 Vancouver province33 Rocky Mountains province

V. Macaronesian region

34 Azores province35 Madeira province36 Canaries province37 Cape Verde province

VI. Mediterranean region

38 Southern Morocco province39 Southwestern Mediterranean province40 South Mediterranean province41 Iberia province42 Baleares province43 Liguria-Tyrrhenia province44 Adriatic province45 East Mediterranean province46 Crimea-Novorossijsk province

VII. Saharo-Arabian region

47 Sahara province48 Egypt-Arabia province

VIII. Irano-Turanian region

49 Mesopotamia province50 Central Anatolia province51 Armenia-Iran province52 Hyrcania province53 Turania or Aralo-Caspia province54 Turkestan province55 Northern Baluchistan province56 Western Himalaya province57 Central Tien Shan province58 Dzungaria-Tien Shan province59 Mongolia province60 Tibet province

IX. Madrean region

61 Great Basin province62 Californian province63 Sonoran province64 Mexican Highlands province

X. Guineo-Congolian region

65 Upper Guinean forests province66 Nigeria-Cameroon province67 Congo province

XI. Usambara-Zululand region

68 Zanzibar-Inhambane province69 Tongoland-Pondoland province

XII. Sudano-Zambezian region

70 Zambezi province71 Sahel province72 Sudan province73 Somalia-Ethiopia province74 South Arabia province75 Socotra province76 Oman province77 South Iran province78 Sindia province

XIII. Karoo-Namib region

79 Namibia province80 Namaland province81 Western Cape province82 Karoo province

XIV. St. Helena and Ascension region

83 St. Helena and Ascension province

XV. Madagascan region

84 Eastern Madagascar province85 Western Madagascar province86 Southern and Southwestern Madagascar province87 Comoro province88 Mascarenes province89 Seychelles province

XVI. Indian region

90 Ceylon (Sri Lanka) province91 Malabar province92 Deccan province93 Upper Gangetic Plain province94 Bengal province

XVII. Indochinese region

95 South Burma province96 Andamans province97 South China province98 Thailand province99 North Indochina province100 Annam province101 South Indochina province

XVIII. Malesian region

102 Malaya province103 Borneo province104 Philippines province105 Sumatra province106 South Malesia province107 Celebes province108 Moluccas and West New Guinea province109 Papua province110 Bismarck Archipelago province

XIX. Fijian region

111 New Hebrides province112 Fiji province

XX. Polynesian region

113 Micronesia province114 Polynesia province

XXI. Hawaiian region

115 Hawaii province

XXII. Neocaledonian region

116 New Caledonia province

XXIII. Caribbean region

117 Central America province118 West Indies province119 Galápagos Islands province

XXIV. region of the Guayana Highlands

120 The Guianas province

XXV. Amazon region

121 Amazonia province122 Llanos province

XXVI. Brazilian region

123 Caatinga province124 Central Brazilian Uplands province125 Chaco province126 Atlantic province127 Paraná province

XXVII. Andean region

128 Northern Andes province129 Central Andes province

XXVIII. Cape region

130 Cape province

XXIX. Northeast Australian region

131 North Australia province132 Queensland province133 Southeast Australia province134 Tasmania province

XXX. Southwest Australian region

135 Southwest Australia province

XXXI. Central Australian or Eremaean region

136 Eremaea province

XXXII. Fernandezian region

137 Juan Fernández province

XXXIII. Chile-Patagonian region

138 Northern Chile province139 Central Chile province140 Pampas province141 Patagonia province142 Tierra del Fuego province

XXXIV. region of the South Subantarctic Islands

143 Tristan-Gough province144 Kerguelen province

XXXV. Neozeylandic region

145 Lord Howe province146 Norfolk province147 Kermadec province148 Northern New Zealand province149 Central New Zealand province150 Southern New Zealand province151 Chatham province152 New Zealand Subantarctic Islands province

References

Phytochorion Wikipedia


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