THE ECOLOGICAL BACKGROUND, DETERIORATION AND RECLAMATION OF DESERT DUNE SAND

The physical properties of desert dune sand are reviewed as part of its ecological characteristics. Sandy soils are known for their superiority to other finer soils in deserts. For this reason, sand dunes in arid lands are covered, as a natural process, by vegetation. The drawback of sand is its mobility: erosion of sand, not lack of moisture, is the major limiting factor for vegetation on dunes. The destruction of vegetation by overgrazing and by being collected for firewood and building material is a relatively quick process. This stimulates sand movement and increases deterioration through positive feedback. Whilst deterioration processes are swift, natural reclamation processes are slow. One way of increasing the productivity of dune sand is by the use of sophisticated methods of agriculture. Unlike sand in humid areas, sand in deserts offers many advantages for agriculture: it is the only soil that endures irrigation with brackish water, and its thermal retention forces crops to ripen quickly. The problem of low and unreliable rainfall in arid lands can be turned to advantage by the use of the drip irrigation method, which allows a rational and economic use of fertilizers without the risk of leaching by subsequent rain.