The dissemination – part 1

The majority of orchids settle as epiphytes in the canopy of trees. They occur mainly in the tropics. Terrestrial orchids grow straight out of the ground. They are mostly restricted to temperate zones.

The dissemination

The orchid family is one of the most extensive in the plant world and is distributed almost all over the world, but not evenly. One records sporadic occurrences as well as the accumulation of genera or. Species in some areas and a major concentration in the two centers, the subtropical-tropical American and the corresponding Asian circle. According to an estimate, around four fifths are to be found in these areas compared to one fifth in the temperate zones. this means, that the number of species decreases with increasing distance from the tropical belt. However, that is not the end of it, because even in the sub-arctic zone species can be identified. Here and in the temperate zones you can only find terrestrial orchids, so earth dwellers. They are perennial plants, in which the climate the strict alternation of rest period – with the drawing in of the above-ground parts of the plant – and growing season. As you get closer to the tropical belt, the number of earth-dwelling orchids decreases, and in the warm zones are the trees- and rock-dwelling species predominantly or alone determining. They are called epiphytes, Growths, who live on the trunks and branches of the trees, without depriving the host plant of food. So they are not parasites.

The climate is decisive for the existence of the epiphytes in many ways. Their spread is regulated by the temperature, but more because of the amount of precipitation and humidity, which must guarantee the balancing of the water balance as the most important factor. As a result, most of the epiphytes are found in areas, where abundant rainfall is distributed throughout the year. This is in a belt of about 24 Latitude given on both sides of the equator. However, almost half of the mainland of this belt is extremely arid. Orchids and especially epiphytes cannot thrive in these vast areas of deserts and semi-deserts on four continents. Their occurrence is concentrated in regions, where the trade winds and monsoon winds – ascending on mountain ranges – give off their moisture masses. The orchids grow most lush and species-rich in the cloud forests, Areas of highest concentration of plants, where the moisture is omnipresent in the finest distribution. However, the temperature then has an effect, descending with increasing altitude, again regulating the existence of the epiphytes. But there are also outsiders here. In the Andes from Colombia to Peru – located directly on the equatorial tropical belt – there are orchid species, those in heights up 4200 m are to be found as the top limit overall for the family. There are several similar examples at a somewhat lower altitude in the south- and Central America. In Asia it is repeated in the Himalayas with a limit up to 2600 m height for a Dendrobium species. At about 2000 to 2400 The well-known Coelogyne cristata grows. This reduced limitation in height is explained by the significantly greater distance to the equator compared to the South American example.

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