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africa namib desert subsurface competition tall grass species sap nutrients

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#1 Hum

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Posted 05 September 2013 - 22:07

The bizarre circular patches of bare land called "fairy circles" in the grasslands of Africa's Namib Desert have defied explanation, with hypotheses ranging from ants to termites to grass-killing gas that seeps out of the soil. But the patches may be the natural result of the subsurface competition for resources among plants, new research suggests.

Grasslands in the Namib Desert start off homogenous, but sparse rainfall and nutrient-poor soil spark intense competition between the grasses, according to the new theory. Strong grasses sap all of the water and nutrients from the soil, causing their weaker neighbors to die and a barren gap to form in the landscape.

The vegetation gap expands as the competition ensues, and the grass-free zone becomes a reservoir for nutrients and water. With the additional resources, larger grass species are then able to take root at the periphery of the gap, and a stable fairy circle develops.

"It's a really good theory because it accounts for all the characteristics of fairy circles," including the presence of tall grass species, Florida State University biologist Walter Tschinkel, who was not involved in the study, told LiveScience. "No other proposed cause for fairy circles has ever done that."

Fairy circles have been a mystery to scientists for decades. Last year, Tschinkel discovered that small fairy circles last for an average of 24 years, whereas larger circles can stick around for up to 75 years. However, his research didn't determine why the circles form in the first place, or why they disappear.

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#2 medhunter

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Posted 06 September 2013 - 03:41

weird





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