资源环境科技发展态势分析平台

By Bethan Ackerley

Quan-Xing Liu

The most famous so-called fairy circles are grass-ringed patches of barren earth found in Namibia and Australia. Their lesser-known cousins – transient rings of plants found in Chinese salt marshes –could help explain why these patterns naturally form and may be indicators of ecosystems resilient to climate change.

Previous research has shown that some self-organising patterns in nature provide insights into ecosystem resilience. But transient ones that change shape over time – for example, from spots to rings and then to concentric rings – haven’t been studied as much as persistent ones like fairy circles that mostly stay the same.

To find out more, Li-Xia Zhao at East China Normal University and her colleagues took sediment and plant samples from transient rings on salt marshes in Shanghai. The rings were made up of two plant species, Scirpus mariqueter and Spartina alterniflora, and were generally between 10 and 100 metres in size. Compared with samples from the rings’ edges, centre samples had higher concentrations of sulphides, which can cause plant death at high levels. The centre samples also had less available soil nitrogen, which can limit plant growth.

These variations at different positions in each ring are caused by the growth and decomposition of the plants. The researchers’ computer models show that both nutrient depletion and rising sulphide levels would lead the vegetation in the centre to die first, as that is where the plant has been growing for the longest, leaving living rings.

These strange patterns of grass aren’t just interesting to look at – they indicate that their environment can bounce back from disruption more easily than others. The researchers’ models show that ecosystems with transient rings recover from disruptions like environmental stress – a lack of oxygen in the sediment, for example – to their previous state twice as quickly as those with persistent ring patterns.

Understanding the dynamics of transient patterns could be useful as climate change intensifies. “It sort of teaches you what the limiting factors for a vegetation are,” says team member Johan van de Koppel at the University of Groningen, the Netherlands. “It’s learning about what determines salt marsh expansion to help then restore them, because they are very important ecosystems. They are carbon absorbers, so they are also important to counter the effect of human CO2 emissions.”

Journal reference: Science Advances, DOI: 10.1126/sciadv.abe1100

Sign up for Wild Wild Life, a free monthly newsletter celebrating the diversity and science of animals, plants and Earth’s other weird and wonderful inhabitants