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Publication Type J
Authors Emberger, L.
Title Apergu general sur la vegetation du Maroc. Veroffentl. Geobot. Forschungsinst
Source Rubel
Abstract The Mediterranean climate is characterized by the coincidence of the cold and wet seasons, the summers being dry. Among Mediterranean climates the Moroccan represents a rather oceanic type, the temp. amplitudes being generally small. The types of climate of Morocco are classified Saharian, arid, semi-arid, sub-humid, humid and alpine Mediterranean climate.[long dash]Saharian: Typical deserts do not exist in Morocco, even the driest places receive small amts. of precipitation each year during the winter. Even outside the river valleys there is a permanent, but very scanty, vegetation, partly dominated by Acacias (A. raddiana, A. seyal and A. gummijera) on sandy soil, partly by smaller bushes or dwarfbushes like Anabasis aretioides on rocky soil. Real desert sand dunes do not occur in Morocco, the small ones occurring are colonized by Aristida pungens, etc. Characteristic sp. of oases: Phoenix dactylijera, Arid region: Climate very dry, represented on the S and E shores of the Mediterranean,it is seldom found in Europe but occupies great areas in Morocco. The warmer types are characterized by open forests, the colder by types by Stipa tenacissima steppes. Vegetation types: 1: Argania spinosa forest, in primitive state rather dense and with abundant undergrowth; grows on all types of soil except loose sand. Approaching the dryer regions, the forest becomes lower and Argania gives way to Euphorbia echinus et al.; along the shores the occurrence of Pistacia and Oiea indicates a semi-arid climate. 2: Zizyphus lotus and Acacia gummifera form extensive scrubs, generally much degraded by pasturage. Great areas are transformed to secondary Stipa tortilis steppes. Soils often show a conc. of soluble salts in upper layers. 3: The Stipa tenacissima steppes on well-drained soil and the Artemisia herba alba communities on heavier soils represent the colder types of arid vegetation, in regions where winter temps, are lower. They also occur in places where the dryer forest types have been destroyed.[long dash]The semi-arid region occupies immense areas in the Mediterranean countries; in Morocco it is found both on the Atlantic and Mediterranean sides, encircling the central mountain massifs. The main difference between this climate and the preceding, greater humidity, is conditioned partly by higher precipitation, partly by lower evaporation. According to the geographical position, the temp. of the coldest month is above or below 0[degree], thus presenting a series of sub-types. The coldest types are characterized by the occurrence of Juniperus thurifera, the intermediate by J. phoenicea, the warmest by a number of plant communities that distribute themselves according to the properties of the soil. 1: Callitris articulata forest. Generally rather indifferent with regard to nature of soil, but near limits of distribution restricted to calcareous soils, being crowded out from other types by competitors. In primeval state the Callitris forest is a rather open forest with high-grown trees with a remarkable number of characteristic spp. 2: Juniperus phoenicea forest. Quite indifferent with regard to the nature of the soil; it substitutes Callitris whenever the climate becomes more continental. However, it does also occur along the coasts, but only on unstabilised sand that cannot be invaded by other spp. J. phoenicea occupies an intermediate altitudinal position between Quercus ilex (above) and Callitris (below), it does not occur in the most oceanic parts, and does not form a pure belt except in the driest, where Callitris does not grow. Most of the J. phoenicea forests are destroyed. The littoral J. phoenicea forests are floristically quite different from the regular type. 3: Juniperus thurifera var. ajricana forests. These replace the J. phoenicea forests in the most continental parts of the semi-arid region, where winter temps. are rather low, chiefly confined to the Grand Atlas Massif. But in other massifs this sp. occurs also in moister situations, forming the timber-line. The low temps. are here conditioned by the altitude. J. thurifera is often the only remains of Cedrus forests, disappeared long ago, the Juniperus surviving as the most resistant sp. Many J. thurifera forests are really reduced cedar forests. Further forest destruction must be prevented as the J. thurifera forests are of very great economical importance. As the forests are very open, their undergrowth is most varied, even including cushion plants from the alpine regions. 4: The Olea-Pistacia-Chamaerops scrub occupies considerable areas, but is confined to heavy clayey soils. As soon as the soil changes, Callitris, Quercus suber or Q. ilex invades. As the community occupied those soils that were best suited for cultivation, it has been almost totally destroyed. The extreme state of degradation is the Chamaerops humilis community. In spring this scrub is characterized by a multitude of flowering plants, to a great extent geophytes, 5: Pinus halepensis forests are rather rare in Morocco, but the recent degradation seems to favor its spreading. The old, relict forests are surrounded by a zone with younger trees. In the dryer parts of Morocco, however, Callitris is favored, as conditions are a little too dry for P. halepensis. The strictly local old P. halepensis forests differ a great deal from each other and constitute 2 different floristic types, one Mediterranean and one Atlantic. 6: Cupressus sempervirens forest is represented in one place. Its floristic composition shows that it is a Juniperus phoenicea forest which has become dominated by Cupressus. 7: The following forest types are represented in the semi-arid region, but have their proper distribution outside it: Aragania forest, Quercus suber forest and Q. ilex forest. The subhumid region is in Morocco restricted to the middle altitudes in the mountains, except in a few places with very great precipitation. 1: Quercus ilex forest. Q. ilex is distributed over great areas and has covered still greater. It is preferably a montane sp. The semi-arid types are low, with an under-growth which is very like that on the Q. suber forest. The primeval Q. ilex forest is composed of trees with straight stems, middle height, very dense and with little undergrowth. Most forests are, however, more open, due to logging operations and the under-growth therefore much richer. 2: Quercus coccifera community (scrub or, rarely, low forest) is restricted to a very limited area in Morocco. 3: Pinus pinaster forests really belong to the humid region, but are represented also in the sub-humid. 4: The Olea-Pistacia-Chamaerops scrub is represented by a type without P. atlantica (but containing P. lentiscus). 5: Quercus suber forests are decidedly calcifuge. They are widely distributed in Morocco and represent very great economic values. During a previous, moister period, the tree had a much greater distribution than today, many isolated outposts must be considered relicts from this period. Some of these belong to the semi-arid region; the famous forest of Mamora also lies within this region, on sandy soil. While the semiarid types are rather open, the subhumid is much denser and the tree crowns form a continuous cover. Both types invade the Olea-Pistacia-Chamaerops scrub where the soil is not clayey. The humid region, in which the Mediterranean character of the climate is less pronounced, occupies smaller areas than the preceding. In the lowlands this type of climate is rare, in the mountains a colder subtype is more distributed. 1: Cedrus atlantica forest occupies an area of 215,000 ha. at present, but very much has been destroyed. It occurs between 15-1600 and 2900 m.s.m., it never forms the timberline. It is curious that Cedrus does not occur, nor does it seem to have occurred in places, e.g., in Grand Atlas, where the climatic conditions seem to favor its occurrence. 2: Abies pinsapo ssp. maroccana occupies a small area, forming forests between 1500 and 2100 m. 3: Quercus tozza also occupies a very small area. 3: Quercus faginea forests do not occupy a very great area, but are widely distributed, indicating a former greater importance. It is a very well established community that cannot be invaded by other spp., but Q. faginea partly invades the surrounding forests. 5: Quercus suber, Q. ilex and Pinus pinaster also occur in small quantities in the humid region. The altitude of the timber-line varies between 28-2900 and 31-3200 m.s.m. It is generally composed by Juniperus thurifera, sometimes by Q. ilex. A sub-alpine scrub-belt is never found.[long dash]The alpine region is decidedly dry, the maximum of precipitation lying lower than the timber-line. The lower alpine region is characterized by the dominance of cushion-plants. Most remarkable stations are formed by soil that is permanently wet. The flora of such places bears a very strong resemblance to the European alpine flora. Chionophilous vegetation is formed by Ranunculus geraniifolius ssp. aurasiacus, Cossonia spp. etc. The highest zone is characterized by a very scattered herb vegetation. The flora is composed of 26 spp., 20 of which are endemic. The most important edaphic vegetation types are those of salt soil, Atriplex halimus, etc., scrub and Spartina stricta ssp. maritima communities, the latter occurring on the seashore. Intermittent lakes, dry in summer, are characterized by a vegetation of Juncus spp. and in the permanently water-covered parts, Phragmites, etc. With regard to all communities mentioned the paper gives an account of distribution and floristic composition. The distribution of Chamaerops humilis and Stipa tenacissima in Morocco is mapped. || ABSTRACT AUTHORS: K. Faegri
Publication Date 1939
Year Published 1939
Volume 14
Beginning Page 40-157
Unique Article Identifier BCI:BCI19391300007192
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