Saturday, 15 July 2006

Soil development by urban land use and management in semi - arid regions, example from Tehran.

Mohammad Baharvand II, Universitaet Duisburg-Essen, Fb. Biologie und Geographie, Dept. Angewandte Bodenkunde, Universitaetsstr. 5, D-45117 Essen, Germany and Wolfgang Burghardt, Universitaet Duisburg-Essen, Fb. Biologie und Geographie, Abt. Angewandte Bodenkunde, Universtitätsstr. 5, d-45117 Essen, Germany.

Soil use in urban areas of semi-arid and arid regions differs from humid regions by intensity and way of management. Life takes place more frequent outside home in streets and parks. For maintenance irrigation plays a major role in park areas as well as cleaning sidewalks with water which will irrigate patches of shrubs and trees along the streets. In some parks the lawn sods and in parts of the play grounds the gravely sand had been replaced. The investigation was done on 9 park lawns, park forests and play grounds, and 10 street sites. The samples were taken as volume samples. The depth intervals of sampling were 0-2, 2-5, 5-10. 19-20 and 20 tom 40 cm. The analyses were water content, bulk density, pH, content of carbonates, C, N, and heavy metals such as Pb, Cd, Zn, Cu from aqua regia extraction. Increased frequency of site use together with in part wet top soils will have effects on bulk density of top soils. It is obvious that the low bulk density of top soils observed on lawn in humid regions does not occur often. Exceptions are urban forest stands. From irrigation leaching effects are expected, particular of carbonates. But there are no indications for this. For pH values there exist already a distinct continuous decrease from sub soil to top soil. C content was high in top soils of park-forest sites due to the forest use. It decreased with depth. This was different for lawn. In the top soil it could be low but increased underneath the sod before a decline occurred with depth. Interesting was the high N content which did result in a narrow C/N relation. Heavy metal content was influenced by the distance to main streets. This was particular obvious for Pb. Effects of leaching were not clear detectable. A major role seems to play the replacement of sods in park areas and of gravely sand on play grounds. Were the replacement was not performed the contents increased distinct. In case of replacement a strong decrease of heavy metals in the top 5 cm occurred. Underneath heavy metal increased. The results show that management in semi-arid area can have strong influences on soil properties and development.

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