Ecologists confirm Alan Turing's theory for Australian fairy circles


Date:
September 22, 2020
Source:
University of Go"ttingen
Summary:
Fairy circles are one of nature's greatest enigmas and most
visually stunning phenomena. Researchers have now collected
detailed data to show that Alan Turing's model explains the
striking vegetation patterns of the Australian fairy circles. In
addition, the researchers showed that the grasses that make up
these patterns act as ''eco-engineers'' to modify their hostile
and arid environment, keeping the ecosystem functioning.



FULL STORY ========================================================================== Fairy circles are one of nature's greatest enigmas and most visually
stunning phenomena. An international research team led by the University
of Go"ttingen has now, for the first time, collected detailed data to
show that Alan Turing's model explains the striking vegetation patterns
of the Australian fairy circles. In addition, the researchers showed
that the grasses that make up these patterns act as "eco-engineers" to
modify their own hostile and arid environment, thus keeping the ecosystem functioning. The results were published in the Journal of Ecology.


========================================================================== Researchers from Germany, Australia and Israel undertook an in-depth
fieldwork study in the remote Outback of Western Australia. They used
drone technology, spatial statistics, quadrat-based field mapping,
and continuous data-recording from a field-weather station. With the
drone and a multispectral camera, the researchers mapped the "vitality
status" of the Triodia grasses (how strong and how well they grew)
in five one-hectare plots and classified them into high- and low-vitality.

The systematic and detailed fieldwork enabled, for the first time
in such an ecosystem, a comprehensive test of the "Turing pattern"
theory. Turing's concept was that in certain systems, due to random disturbances and a "reaction-diffusion" mechanism, interaction between
just two diffusible substances was enough to allow strongly patterned structures to spontaneously emerge. Physicists have used this model
to explain the striking skin patterns in zebrafish or leopards for
instance. Earlier modelling had suggested this theory might apply to
these intriguing vegetation patterns and now there is robust data from
multiple scales which confirms that Alan Turing's model applies to
Australian fairy circles.

The data show that the unique gap pattern of the Australian fairy circles, which occur only in a small area east of the town of Newman, emerges
from ecohydrological biomass-water feedbacks from the grasses. In fact,
the fairy circles -- with their large diameters of 4m, clay crusts from weathering and resultant water run-off -- are a critical extra source of
water for the dryland vegetation. Clumps of grasses increased shading
and water infiltration around the nearby roots. With increasing years
after fire, they merged more and more at the periphery of the vegetation
gaps to form a barrier so that they could maximize their water uptake
from the fairy circle's runoff. The protective plant cover of grasses
could reduce soil-surface temperatures by about 25DEGC at the hottest
time of the day, which facilitates the germination and growth of new
grasses. In summary, the scientists found evidence both at the scale of
the landscape and at much smaller scales that the grasses, with their cooperative growth dynamics, redistribute the water resources, modulate
the physical environment, and thus function as "ecosystem engineers"
to modify their own environment and better cope with the arid conditions.

Dr Stephan Getzin, Department of Ecosystem Modelling at the University
of Go"ttingen, explains, "The intriguing thing is that the grasses are
actively engineering their own environment by forming symmetrically
spaced gap patterns.

The vegetation benefits from the additional runoff water provided by
the large fairy circles, and so keeps the arid ecosystem functional
even in very harsh, dry conditions." This contrasts with the uniform
vegetation cover seen in less water-stressed environments. "Without the self-organization of the grasses, this area would likely become desert, dominated by bare soil," he adds. The emergence of Turing-like patterned vegetation seems to be nature's way of managing an ancient deficit of
permanent water shortage.

In 1952 when the British mathematician, Alan Turing, published his
ground- breaking theoretical paper on pattern formation, he had most
likely never heard of the fairy circles before. But with his theory
he laid the foundation for generations of physicists to explain highly symmetrical patterns like sand ripples in dunes, cloud stripes in the sky
or spots on an animal's coat with the reaction-diffusion mechanism. Now, ecologists have provided an empirical study to extend this principle
from physics to dryland ecosystems with fairy circles.


========================================================================== Story Source: Materials provided by University_of_Go"ttingen. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Stephan Getzin, Todd E. Erickson, Hezi Yizhaq, Miriam
Mun~oz‐Rojas,
Andreas Huth, Kerstin Wiegand. Bridging ecology and physics:
Australian fairy circles regenerate following model assumptions
on ecohydrological feedbacks. Journal of Ecology, 2020; DOI:
10.1111/1365-2745.13493 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/09/200922102429.htm

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