Researchers have developed a new model explaining the mysterious fairy circles in grasslands, integrating plant phenotypic plasticity and spatial self-organization. Their findings, offering insights into ecosystem resilience under water stress, highlight the need for a more complex understanding of ecosystems in changing climates.
After extensive research and unsatisfactory alternative explanations, Prof. Ehud Meron and his team believe pairing spatial patterning and phenotypic changes provides the answer.
Fairy circles, characterized by their almost hexagonal pattern of circular bare-soil gaps amidst grasslands, were first discovered in Namibia and subsequently in various global locations. These intriguing formations have captivated and perplexed scientists for a considerable time.
Speculations about their origin include a range of theories, from the concept of spatial self-organization driven by the interaction between water availability and vegetation dynamics, to the possibility of these patterns being influenced by the underlying distribution of termite nests.
Prof. Ehud Meron of Ben-Gurion University of the Negev has been studying the Namibian fairy circles as a case study for understanding how ecosystems respond to water stress.
He believes that all theories to date have overlooked the coupling between two robust mechanisms essential for understanding ecosystem response: phenotypic plasticity at the level of a single plant, and spatial self-organization in vegetation patterns at the level of a plant population. Phenotypic plasticity is the plant’s ability to change its own traits in response to environmental stresses.
Novel Model and Findings
Prof. Meron, together with his postdoctoral fellows, Jamie Bennett, Bidesh Bera, and Michel Ferré, and his colleagues, Profs. Hezi Yizhaq and Stephan Getzin, propose a novel model that captures both spatial patterning by a scale-dependent water-vegetation feedback and phenotypic changes involving deep-root growth to reach a moister soil layer.
By comparing model predictions with empirical observations, they show that the coupling between these two mechanisms is the key to resolving two outstanding puzzles that the classical theory of vegetation pattern formation fails to explain: the appearance of multi-scale fairy-circle patterns, where the matrix in between the fairy circles consists of small-scale vegetation spots, and the absence of stripe and spot patterns, besides gap patterns, along the rainfall gradient, as the classical theory predicts.
Furthermore, they find that the combination of plant-level phenotypic changes and population-level spatial patterning can result in many additional pathways of ecosystem response to water stress, resulting in different multi-scale patterns, all of which are significantly more resilient to water stress than those involving a single phenotype.
Their findings were recently published in the Proceedings of the National Academy of Sciences (PNAS).
“Identifying these alternative pathways is essential for shifting fragile ecosystems on tracks to collapse to pathways of resilience,” explains Prof. Meron, who recently won an ERC Synergy Grant to study resilience pathways in drylands and other biomes. “This study highlights the importance of considering more elements of ecosystem complexity when addressing how to evade tipping to dysfunctional ecosystem states as warmer and drier climates develop,” Prof. Meron concludes.
Reference: “Phenotypic plasticity: A missing element in the theory of vegetation pattern formation” by Jamie J. R. Bennett, Bidesh K. Bera, Michel Ferré, Hezi Yizhaq, Stephan Getzin and Ehud Meron, 7 December 2023, Proceedings of the National Academy of Sciences.
DOI: 10.1073/pnas.2311528120
The Israel Science Foundation supported this research under grants no. 1053/17 and 2167/21.
Source: SciTechDaily
