HYDRO- ECONOMICAL TYPES IN THE VEGETATION OF NEAR EAST 



DESERTS 



Professor M. Zohary 



(Jerusalem) 



This paper presents readily comparable data on the hydro- ecological behaviour 

 of the leading species of the most common plant communities representative of the 

 Near East deserts. 



The Near East deserts comprise a vast trapezoid limited by the Syro- Palestine 

 mountain system to the west and by the Zagros mountains to the east. In the north 

 it merges into southern Anatoly and in the south it is bordered by a line drawn from 

 Suez Gulf to the Gulf of Aqaba. 



The climate of these deserts is an extreme variety of the Mediterranean type, 

 characterized by mild to fairly cold and rainy winters and dry hot summers. The 

 mean monthly winter temperature never drops below 0°C. The bulk of the area (a- 

 bout 80%) is situated between the isohytes of 200 and 50mm and the monthly dis- 

 tribution of the rainfall is very unstable. 



Although rather uniform in the physiognomy of its vegetation, the area under re- 

 view consists of two plant- geographical territories, the Irano- Turanian in the north 

 and the Saharo- Sindian in the south (Eig. 1938). 



The observations and measurements recorded here were made mainly in the fol- 

 lowing plant associations: Association of Artemisia monosperma - Convolvulus 

 lanatus (on the eastern fringes of the coastal sand dunes); Haloxyletum articulati 

 (on sandy loess); Zygophylletum dumosi (on hammada); Acacietum tortilidis (in 

 runnels crossing sterile hammada); and Haloxyletum persici (on interior sand dunes 

 derived from Cretaceous Nubian Sandstone and crystalline rocks). 



Pheno - Ecology 



3y pheno- ecology I mean those seasonal changes in the plant organs which 

 affect, directly or indirectly, the water economy of the plant. An analysis of the 

 flora of the area concerned has led to the distinction of the following types (Fig. 1). 



(a) Acacia type. Evergreen trees shedding the old leaves or green branches after 

 the formation of the new ones, so that defoliation never occurs. Time of leaf- 

 fall — summer. (Acacia raddiana, A. spirocarpa, Tamarix spp.). 



(b) Anabasis type. Evergreen, articulate stem succulents producing new assimi- 

 lating branches in winter, while certain portions of older branches die back in 

 the summer (Anabasis articulata, Haloxylon articulatum, H. salicomicum, etc.). 



(c) Retama type. Evergreen spartoids, shedding their leaves in early winter (Re- 

 tama roetan, Calligonum comosum, etc.). 



(d) Lycium type. Wintergreen phanerophytes shedding all their leaves in midsum- 

 mer (Lycium arabicum, Anagyris foetida, etc.). 



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