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Once Land Is Completely Barren, It Can't Bloom Again

A theoretical study of desertification, the process by which semiarid plant vistas turn into deserts, explains for the first time how plant growth changes as precipitation levels decrease.

The model, developed by investigators at Ben-Gurion University of the Negev and its Jacob Blaustein Institute of Desert Research (BIDR), was published recently in the leading journal of the American Physical Society, Physical Review Letters. Authors include Dr. Jost von Hardenberg, Prof. Ehud Meron, Prof. Yair Zarmi and Prof. Moshe Shachak.

Their published calculations show that amply watered areas, characterized by uniform plant coverage, develop small bald spots when rainfall is less than optimal.

With increasing aridity, these bald blemishes expand, and plants adopt banded or labyrinth-like patterns.

When rainfall gets even more scarce, the bands break down into dashed or small circular patches, which may disappear altogether when hyperarid conditions take over.

All of these vegetation patterns have been observed in many areas of the world, including Israel's Negev desert.

The BIDR model also accounts for the near irreversibility of desertification, as it indicates that once land is completely barren, it will remain so even if rainfall were to return to levels that previously supported spotted or banded vegetative growth.

This essential finding stems from calculations showing that in a particular precipitation range, both patterned vegetation and bare ground are stable solutions. In other words, existing perennial plants with well-developed root systems are able to trap water efficiently and thereby survive even under relatively arid conditions, while seeds attempting to colonize already desolate areas need greater ground dampness to prevail.

[Contact: E. Tepper]






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