3. The Desert Vegetation 



The vegetation of Bahrain comprises three formations or major communities of spe- 

 cies of which two are local, one of these being largely adventive. 



Most restricted in distribution is the halophytic vegetation of muddy shores, namely 

 salt marsh and mangrove swamp, which occurs especially on parts of the shores of the 

 deep inlet a mile or two south of Manama and more sporadically near Sitra. 



More extensive but still local is the mainly adventive flora of the date and other 

 gardens in the cultivated northern part of the peripheral zone, where constant irrigation 

 is practised. 



Everywhere else on the island the vegetation is one or other minor facies of a 

 single rich but highly selected desert plant community of the general North African — 

 Indian desert flora, — comprising something less than 200 species. Nowhere on the is- 

 land, with the two exceptions already noted, is climate, soil, altitude or any other in- 

 fluence sufficient to cause any real replacement or even important modification of this 

 general plant community. 



The natural desert areas of Bahrain, that is to say the whole island outside the 

 cultivated part of the peripheral zone, displays well the three most prevalent kinds of 

 desert habitat, namely sandy or small -dune desert; stony and gravelly desert, or reg; 

 and rock exposures, or hamada, as well as one or two particular conditions. 



A. Sandy desert, in which the substrate is so loose as to pile up to some extent at 

 least against the larger plants, is the characteristic condition of the peripheral zone 

 and occurs also here and there in the saucer, especially in the south-east, where wind- 

 borne material tends to accumulate. Its vegetation is often more considerable in bulk 

 than that of the other deserts because some of the individuals are larger (e.g. Lepta- 

 denia pyrotechnic a) but the species are fewer and of a more halophytic sort. In one di- 

 rection this type of desert passes towards plantless loose sand and in the other towards 

 consolidated salt flats such as are found north of Mattala and here and there elsewhere . 



B. Stony and gravelly desert is also widespread and, to the eye at least, is the most 

 characteristic feature of the island, since it prevails in the more accessible parts, cov- 

 ering practically all the flanks of the central dome and parts of the central plateau. The 

 surface is of more or less consolidated sand or marl, thickly or even completely covered 

 with irregular and angular pieces of flint, chert or limestone, ranging from a quarter of 

 an inch to several inches in diameter, generally white or pale yellow but often black 

 and frequently modified in colour by grey -green or yellow lichens, which are a conspic- 

 uous feature of these deserts. This stony desert surface is presumably the result of 

 denudation in situ and it is here that the tumuli are so numerous, and from this material 

 that they are made. The vegetation is on the whole sparse, especially towards the tops 

 of the slopes, and there are often distances of many feet between neighbouring plants, 

 but it becomes much thicker wherever a slight cavity or consolidation (as, for instance, 

 wheel ruts) retains the intermittent rainfall a little longer than elsewhere. Such depres- 

 sions are especially numerous between the tumuli and here the vegetation is often al- 

 most closed. The surface of the tumuli resembles that of the plain and they tend to 

 bear a slightly depauperated mixture of the same species, with notably more individuals 

 on their northern sides. 



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