Afghanische Pflanzengesellschaften

Summary

In a region where transpiration amounts to about 7 times the average of precipitation per annum, mesophilic and hydrophilic plant-communities are limited to habitats where either the ground is impenetrable to water and thus retains rain-water or where running water is present all the year round or where climatic factors supply a higher degree of moisture. Though such habitats are extremely limited the number of different mesophilic or hygrophilic plant-communities is rather high. In spite of this fact even in these communities associations with typical character- or differential species are scarcely developed as the distance from one community to the next is often very great. Therefore seed dispersal is a matter of chance and also local differences in the climatic factors play an important part.

Hygro- and xerophilic communities liable to occasional flooding in spring and to exsiccation in summer are: Cynodontetum dactylontis, Juncetum Gerardi, Aeluropetum, Glaucetum maritimae and Cyperetum fusci. Almost permanently slightly submerged communities are: Heleocharetum uniglumis, Sparganietum ramosi, Juncetum lampocarpi, Typhetum and Phragmitetum australis. Among the communities that permanently need even a higher cover of water are: Nasturtietum officinalis, Batrachieto-Zannichellietum, Acoretum calami, Scirpetum maritimi, Potamogetonetum filiformis and Myriophylletum spicati.

The mesophilic communities are either shrubless and meadow-like such as: Agrostidetum albae, Caricetum alpinae, Poetum annuae, Trichopheretum pumili, Plantaginetum gentianoidis, or shrubs play a more important part as in the Saliceto-Hippophaetum and in the Populeto-Arundinetum, or they consist of high perennials as the Heracleetum persici and the Ligularietum Thomsonii, or they are growing in moist fissures of rocks as the Adiantetum capilli Veneris, Oxyrietum digynae and Cortusetum himalaicae.