Thursday, 13 July 2006

Does Land Use or Climate Dominate Landscape Transformation? A Re-Examination of Historic Landscape Development in the Decapolis Region (Northern Jordan).

Bernhard Lucke1, Michael Schmidt1, Rupert Baeumler2, and Ziad Al-Saad3. (1) Brandenburg University of Technology Cottbus, P.O. Box 101344, Cottbus, 03013, Germany, (2) Friedrich-Alexander University Erlangen-Nuernberg, Kochstr. 4/4, Erlangen, D-91054, Germany, (3) Yarmouk University, Faculty of Archaeology and Anthropology, Irbid, Jordan

It is widely accepted that significant soil erosion took place in cultural landscapes of the Near East, caused by historic land use, and leading to a strong decline of settlements. Based on this idea, extensive development projects were launched, aiming to implement soil conservation measures in order to combat desertification. A detailed study of soil development by physical and chemical examinations in the Decapolis region (Northern Jordan) revealed distinct patterns of soil development, which make intense erosion due to historic land use unlikely. It seems that land use played a significant role for soil development, but did not simply lead to deterioration. Land use intensities and periods might be reconstructed according to soil properties and material culture, as distinct soil development stages are present on one and the same geological and relief units, while historic sources, aerial photos and archaeological material suggest a connection of soil development and land use. Additionally, the small-scale distribution of soil properties seems to be related to a long-term effect of ploughing, which led to a levelling of a once undulating landscape in the Decapolis region. While it is not yet clear whether bedrock or aeolian deposits are the main parent material of Mediterranean soils in Jordan, it seems evident that the present landscape mirrors the transformation due to historic land use and bedrock properties. Accelerated erosion is present only locally, and both soil forming and eroding processes seem to be governed by climate. Here, moist periods are most probably not connected with erosion, but led to plant growth and enhanced soil weathering with or without aeolian input. Buried red Mediterranean soils and wadi sediments point to droughts being most important for erosion, as these periods seemingly witnessed an increased number of extreme precipitation events combined with reduced vegetation. Future management plans should focus on integrated land management practise rather than sole soil conservation measures, which proved to have little effect.

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