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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 province 2 Atlantic Europe province 3 Central Europe province 4 Illyria or Balkan province 5 Pontus Euxinus province 6 Caucasus province 7 Eastern Europe province 8 Northern Europe province 9 Western Siberia province 10 Altai-Sayan province 11 Central Siberia province 12 Transbaikalia province 13 Northeastern Siberia province 14 Okhotsk-Kamchatka province 15 Canada incl. Great Lakes province

II. Eastern Asiatic region

16 Manchuria province 17 Sakhalin-Hokkaidō province 18 Japan-Korea province 19 Volcano-Bonin province 20 Ryūkyū or Tokara-Okinawa province 21 Taiwan province 22 Northern China province 23 Central China province 24 Southeastern China province 25 Sikang-Yuennan province 26 Northern Burma province 27 Eastern Himalaya province 28 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 province 31 North American Prairies province

IV. Rocky Mountain Floristic Region

32 Vancouver province 33 Rocky Mountains province

V. Macaronesian region

34 Azores province 35 Madeira province 36 Canaries province 37 Cape Verde province

VI. Mediterranean region

38 Southern Morocco province 39 Southwestern Mediterranean province 40 South Mediterranean province 41 Iberia province 42 Baleares province 43 Liguria-Tyrrhenia province 44 Adriatic province 45 East Mediterranean province 46 Crimea-Novorossijsk province

VII. Saharo-Arabian region

47 Sahara province 48 Egypt-Arabia province

VIII. Irano-Turanian region

49 Mesopotamia province 50 Central Anatolia province 51 Armenia-Iran province 52 Hyrcania province 53 Turania or Aralo-Caspia province 54 Turkestan province 55 Northern Baluchistan province 56 Western Himalaya province 57 Central Tien Shan province 58 Dzungaria-Tien Shan province 59 Mongolia province 60 Tibet province

IX. Madrean region

61 Great Basin province 62 Californian province 63 Sonoran province 64 Mexican Highlands province

X. Guineo-Congolian region

65 Upper Guinean forests province 66 Nigeria-Cameroon province 67 Congo province

XI. Usambara-Zululand region

68 Zanzibar-Inhambane province 69 Tongoland-Pondoland province

XII. Sudano-Zambezian region

70 Zambezi province 71 Sahel province 72 Sudan province 73 Somalia-Ethiopia province 74 South Arabia province 75 Socotra province 76 Oman province 77 South Iran province 78 Sindia province

XIII. Karoo-Namib region

79 Namibia province 80 Namaland province 81 Western Cape province 82 Karoo province

XIV. St. Helena and Ascension region

83 St. Helena and Ascension province

XV. Madagascan region

84 Eastern Madagascar province 85 Western Madagascar province 86 Southern and Southwestern Madagascar province 87 Comoro province 88 Mascarenes province 89 Seychelles province

XVI. Indian region

90 Ceylon (Sri Lanka) province 91 Malabar province 92 Deccan province 93 Upper Gangetic Plain province 94 Bengal province

XVII. Indochinese region

95 South Burma province 96 Andamans province 97 South China province 98 Thailand province 99 North Indochina province 100 Annam province 101 South Indochina province

XVIII. Malesian region

102 Malaya province 103 Borneo province 104 Philippines province 105 Sumatra province 106 South Malesia province 107 Celebes province 108 Moluccas and West New Guinea province 109 Papua province 110 Bismarck Archipelago province

XIX. Fijian region

111 New Hebrides province 112 Fiji province

XX. Polynesian region

113 Micronesia province 114 Polynesia province

XXI. Hawaiian region

115 Hawaii province

XXII. Neocaledonian region

116 New Caledonia province

XXIII. Caribbean region

117 Central America province 118 West Indies province 119 Galápagos Islands province

XXIV. region of the Guayana Highlands

120 The Guianas province

XXV. Amazon region

121 Amazonia province 122 Llanos province

XXVI. Brazilian region

123 Caatinga province 124 Central Brazilian Uplands province 125 Chaco province 126 Atlantic province 127 Paraná province

XXVII. Andean region

128 Northern Andes province 129 Central Andes province

XXVIII. Cape region

130 Cape province

XXIX. Northeast Australian region

131 North Australia province 132 Queensland province 133 Southeast Australia province 134 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 province 139 Central Chile province 140 Pampas province 141 Patagonia province 142 Tierra del Fuego province

XXXIV. region of the South Subantarctic Islands

143 Tristan-Gough province 144 Kerguelen province

XXXV. Neozeylandic region

145 Lord Howe province 146 Norfolk province 147 Kermadec province 148 Northern New Zealand province 149 Central New Zealand province 150 Southern New Zealand province 151 Chatham province 152 New Zealand Subantarctic Islands province

References

Phytochorion Wikipedia


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