The origin of “jinn circles” in Namibia has puzzled scholars for almost half a century. These are strange circles of sand without grass in places where there is a lot of grass, they form and disappear years later for an unknown reason.
Scientists have long attributed these red circles, especially those found in the grasslands of Namibia and northwestern Australia, to either termites or plants having somehow self-organized.
Now, a team of scientists from the University of Göttingen in Germany has found new evidence supporting the self-regulation theory, in which previous research has attempted to explain the nature of the mysterious “genie circles” found in the Namib Desert, the world’s oldest desert along the coast of Namibia, southwest Africa and western Australia. .
Based on two “exceptionally good” rainy seasons in the Namib Desert, the scientists showed that weeds in “good circles” died immediately after the rains, but termite activity did not result in bare patches.
Continuous measurements of soil moisture show that weeds around circles greatly deplete water inside circles and therefore can lead to death of weeds inside circles.
According to the results published in the journal Perspectives in Plant ecology, evolution and taxonomy, grasses form these circles 2 to 10 meters wide to make the most of the scarce rains.
About 80-140 km from the coast in the Namib there are millions of “even circles”, each several meters wide, which together form a distinct pattern, visible for miles around.
Scientists monitored sporadic rainfall in several areas of this desert and studied weeds, their roots and shoots, as well as possible root damage caused by termites.
Termites, tiny insects that live in large colonies around the world, are often blamed for the death of weeds.
Scientists have paid great attention to the study of the conditions for the death of weeds in the “circles of genies” immediately after the rains, which led to a new growth of weeds.
In addition, they installed soil moisture sensors in and around the trails to record soil and water content at 30-minute intervals from the 2020 dry season to the end of the 2022 rainy season.
Scientists are puzzled over Origin of Fairy circles in Namibia for Near half a century. He boiled down up to two main theories: either the termites were responsible, or the plants somehow self-organized. https://t.co/mR0wVjTi7Srice.twitter.com/tCMeAFkZY4
— Namibian (@TheNamibian) October 23, 2022
This allowed the scientists to accurately record how the growth of newly emerging weeds around the circles affects the soil water in and around the circles. They studied the differences in water infiltration between on and off circuits in ten regions of the Namib Desert.
The data shows that after about ten days of rain, the grasses inside the circles were already dying off, while in most of the inner circles, the grass did not grow at all. After twenty days of rain, the grasses inside the circles were completely dead and yellow, while the surrounding grasses were bright and green.
When the team examined the grass roots inside the circles and compared them to the green grasses outside, they found that the roots inside the circles were longer or longer than those outside. This indicates that the weeds were trying to take root in search of water. However, scientists have found no evidence that termites feed on roots.
It wasn’t until fifty to sixty days of rain that damage to the roots of the dead weeds became more apparent.
Dr. Stefan Götzen from the Department of Ecosystem Modeling at the University of Göttingen explains: “The sudden absence of grass in most areas inside the circles cannot be explained by termite activity, because these insects do not have biomass to feed on. the important thing is that we can show that the termites are not to blame, because the weeds die right after the rains without any sign that the creatures are feeding on the roots.”
When the team analyzed data on soil moisture fluctuations, they found that the decrease in soil moisture inside and outside the circles was very slow after the first rains, when weeds had not yet settled. However, when the surrounding weeds were established, the decline in soil moisture levels after the rains was very rapid in all areas, although there were almost no weeds in the circles that could absorb water.
Gitzen explains: “In the extreme heat of the Namib, weeds constantly penetrate the soil and lose water. Consequently, they create voids for moisture in the soil around their roots, and water is attracted to them. Our results are in complete agreement with the results of researchers who showed that water in soil quickly and horizontally diffuses in this sand even over distances of more than seven meters.
“By forming highly ornamental landscapes with evenly distributed fauna, weeds act as ecosystem architects and directly benefit from the water resources provided by vegetation interruption. Indeed, we know related self-organizing plant structures from various other harsh drylands,” adds Götzen. world, and in all these cases, plants have no other chance for survival than to grow in precisely such geometric formations.
This study may help to understand such ecosystems, especially in relation to climate change, as plant self-regulation protects against the negative effects of increased drought.