Phenotypic plasticity: A missing element in the theory of vegetation pattern formation

What is it about?

Climate change and the development of drier climates threaten ecosystems’ health and the services they provide to humans. Understanding the response of ecosystems to drier climates may provide clues on how to improve their resilience. Two robust mechanisms that improve ecosystem resilience are phenotypic changes in individual plants and partial mortality of plant populations to form vegetation patterns. In nature, these mechanisms are likely to act in concert, but their interplay has escaped consideration. We demonstrate the need for a theory that integrates these plant- and population-level mechanisms by addressing the fascinating fairy-circle phenomenon in Namibia. We show that such an integration resolves two outstanding puzzles in the current theory and highlight its importance in uncovering resilient ecosystem-response pathways.

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Why is it important?

Understanding ecosystem response to drier climates is of utmost importance for maintaining ecosystem function and the services ecosystems provide to humans in the current era of climate change. Our study deepens this understanding by considering for the first time the combined effects of two response mechanisms of dryland ecosystems: a) spatial self-organization in regular vegetation patterns, such as the fairy circles. b) phenotypic plasticity, that is, the ability of a plant to change its traits in response to water and other stresses, such as growing deep roots to reach moister soil layers. Using the Namibian fairy circles as a case study and a novel mathematical model that captures the two response mechanisms, we resolve two outstanding fairy circle puzzles and thereby demonstrate the importance of considering the interplay between the two mechanisms. Importantly, besides solving these puzzles, we find that this interplay results in significantly higher resilience to water stress compared to the resilience that each mechanism alone provides.