Soil sodium and potassium adsorption ratio along a Mediterranean–arid transect |
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Authors: | P Sarah |
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Institution: | Department of Geography, Laboratory of Geomorphology and Soils, Bar-Ilan University, Ramat Gan 52900, Israel |
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Abstract: | Changes in the relationship between soil soluble ions and rainfall were studied on hillslopes at seven research sites that represent four climatic regions: Mediterranean, semi-arid, mildly arid and arid. At each site, soil samples were taken in several seasons and the ratio between the Na+ plus K+ content and the Ca2+ plus Mg2+ content (sodium and potassium adsorption RATIO=SPAR) was determined. In general, SPAR increased with increasing aridity except for the most arid site in which the soil contains a gypsic layer. The relationship between SPAR and rainfall was non-linear. An abiotic threshold, characterized by a sharp change in the SPAR, was found around the 200 mm isohyet: sites that receive less than 200 mm annual rainfall showed significantly higher SPAR than those that receive more than 200 mm, where SPAR was very low. |
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Keywords: | Soil soluble ions Sodium adsorption ratio Potassium adsorption ratio Land degradation Climatic transect Gypsic layer |
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