![Drone image of a car driving through the NamibRand Nature Reserve, one of Namibia's fairy ring regions where researchers undertook grass excavations, soil moisture and infiltration measurements (April 2022 ). Credit: Dr Stephan Getzin Secrets of Namibia's fairy circles debunked: Plants organize themselves](https://oponame.com/wp-content/uploads/2022/10/Secrets-of-Namibias-fairy-circles-debunked-Plants-organize-themselves.jpg)
Drone image of a car driving through the NamibRand Nature Reserve, one of Namibia’s fairy ring regions where researchers undertook grass excavations, soil moisture and infiltration measurements (April 2022 ). Credit: Dr Stephan Getzin
Scientists have wondered about the origin of Namibia’s fairy circles for nearly half a century. It boiled down to two main theories: Either the termites were responsible, or the plants somehow self-organized. Now researchers from the University of Göttingen, taking advantage of two seasons of exceptionally good rainfall in the Namib Desert, show that grasses in fairy circles died immediately after the rain, but termite activity did not. not caused the stripped patches.
Instead, continuous soil moisture measurements demonstrate that the grasses around the circles greatly depleted the water inside the circles and thus likely induced the death of the grasses inside the circles. The results were published in Perspectives in plant ecology, evolution and systematics.
About 80-140 kilometers from the Namib coast there are millions of fairy circles – circular holes in the grassland, each a few meters wide, together forming a distinctive pattern across the entire landscape and visible to kilometers around. Researchers tracked sporadic rains in several areas of this desert and examined grasses, their roots and shoots, and potential termite-induced root damage.
Termites, tiny insects that live in large colonies around the world, have often been blamed for the death of grasses. The researchers took great care to investigate the circumstances of the death of the grasses in the fairy circles just after the rain, which triggered the new growth of the grasses. Additionally, they installed soil moisture sensors in and around the fairy circles to record soil water content at 30-minute intervals from the 2020 dry season until the end of the rainy season. rains 2022.
![Researchers have investigated the death of grass in fairy circles in several regions of the Namib. The roots of the yellowish dead grasses inside the fairy circles are as long and as intact as the roots of the vital green grasses outside the circles. There was no sign of termite activity. Credit: Dr Stephan Getzin Secrets of Namibia's fairy circles debunked: Plants organize themselves](https://oponame.com/wp-content/uploads/2022/10/1666320175_736_Secrets-of-Namibias-fairy-circles-debunked-Plants-organize-themselves.jpg)
Researchers have investigated the death of grass in fairy circles in several regions of the Namib. The roots of the yellowish dead grasses inside the fairy circles are as long and as intact as the roots of the vital green grasses outside the circles. There was no sign of termite activity. Credit: Dr Stephan Getzin
This allowed the researchers to record precisely how the growth of newly emerging grasses around the circles affected the soil water in and around the circles. They studied the differences in water infiltration between the inside and outside of the circles in ten regions of the Namib.
The data shows that about ten days after the rain, the grasses were already starting to die in the circles while most of the inner area of the circles had no grass sprouts at all. Twenty days after the rain, the grasses struggling in the circles were completely dead and yellowish in color while the surrounding grasses were alive and green.
When the researchers looked at the roots of the grasses inside the circles and compared them to the green grasses outside, they found that the roots inside the circles were as long, or even longer, than those outside. the outside. This indicated that the grasses were straining root growth in search of water. However, the researchers found no evidence that the termites fed on roots. It wasn’t until fifty to sixty days after the rain that the root damage became more noticeable in the dead grasses.
Dr Stephan Getzin, from the Department of Ecosystem Modeling at the University of Göttingen, explains that “the sudden absence of grass for most areas inside the circles cannot be explained by termite activity. because there was no biomass for these insects to feed on. But more importantly, we can show that the termites are not responsible because the grasses die off immediately after the rain with no sign of the creatures feeding on the root. “
When the researchers analyzed data on soil moisture fluctuations, they found that the decline in soil water inside and outside the circles was very slow after the first rains, when the grasses were not yet established. However, when the surrounding grasses were well established, the decline of soil water after rains was very rapid in all areas, even though there were almost no grasses in the circles to take up water. .
Getzin explains that “under the high heat of the Namib, the grasses are constantly sweating and losing water. Thus, they create voids of soil moisture around their roots and water is drawn towards them. Our results agree strongly with those of the researchers who have shown that water from the ground diffuses rapidly and horizontally in these sands even over distances greater than seven meters.
Getzin adds that “by forming strongly patterned landscapes of evenly spaced fairy circles, grasses act as ecosystem engineers and directly benefit from the water resource provided by vegetation gaps. In fact, we know of structures of related self-organizing vegetation from various other harsh arid lands around the world, and in all these cases the plants have no other chance of surviving than by growing in exactly such geometric formations.”
This research has implications for understanding similar ecosystems, especially with respect to climate change, as plant self-organization buffers against the negative effects induced by increased aridification.
Researchers go deep into fairy circles
Stephan Getzin et al, Plant water stress, not termite herbivory, causes Namibia’s fairy circles, Perspectives in plant ecology, evolution and systematics (2022). DOI: 10.1016/j.ppees.2022.125698
Provided by the University of Göttingen
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