دراسة تحليلية للنظام البيئي لبعض الواحات الصحراوية غربي العراق للفترة من عام 1966 و لغاية 2009

الملخص EN

To analyze the ecosystem of some Iraq,s western desert oasis, Three oasis were selected [98- kilometers (O-98), Aleksheiti (OK) and Fehida (OF)] which are formed from sand limestone origin materials, located within the secondary physiographic unit lower valley plain in the western desert of Iraq.

The representative pedons were discover within every selected oasis, and every pedon was morphologically described, taking disturbed soil samples from every horizon to analyze the physical and chemical properties.

Soils were classsified according to USDA soil classification 1998.

The climatic data of three meteorological stations nearby the selected oasis, (Ramadi, Haditha and Ana stations) were collected, for the period from 1966 to 2009 to compare them with the data for the period before 1966 to study the variations occurred in the region.

The present ecosystem was analyzed through quantitative measurements for some traits of the vegetation commmunity.

Results can be summarized as follows: Studied physical properties showed that O-98 soils texture was ranged between sandy clay and clay loam, while (OF) and (OK) soils texture was ranged between clay loam and sandy loam.

The soil electrical condductivity values were higher (8.1 dS.m-1) at O-98 soils, while it was lower (5.9 dS.m-1) at (OF) soils, however soil reaction (pH) ranged between 7.4 to 8.1 because of the higher content of calcium carbonate in the soils, which ranged between 16.1% to 49.9%, the soil content of organic matter and gypsum was low.

The preseent climatological data showed, obvious increase in the annual mean temperature, evaporation rate and soil temperature at 50 cm depth, while there was decline in the rainfall rate when compared with climatological data for period before 1966.

Ecosystem analysis indicated that perennial species were ranged between 40% to 61.4%, compared with seasonal species which ranged between 38.5% and 60.0%.

When we compared the present vegetation species with those indicated by Guest (1966), due to variations in the physical environmment within these oasis, we notice a disappear of some species