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 200mm isohyet: sites that receive less than 200mm annual rainfall showed significantly higher SPAR than those that receive more than 200mm, where SPAR was very low.
Original language | English |
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Pages (from-to) | 731-741 |
Number of pages | 11 |
Journal | Journal of Arid Environments |
Volume | 59 |
Issue number | 4 |
DOIs | |
State | Published - Dec 2004 |
Bibliographical note
Funding Information:Financial support was provided by the Israeli Ministry of Science and the Arts, GSF-Forschungszentrum fur Umwelt und Gesundheit GMBH, Neuherberg, Germany (DISUM-029) and the Commission of the European Union (research project MEDALUS III, contract ENV4-CT95-0115). I thank Dr. Jeff Herrick and the other anonymous reviewer for their enlightening and helpful comments.
Keywords
- Climatic transect
- Gypsic layer
- Land degradation
- Potassium adsorption ratio
- Sodium adsorption ratio
- Soil soluble ions