Silicon and the plant economics spectrum: a trait-based approach at the interface of physiological and ecosystem ecology.

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Over the past three decades, plant ecologists have become increasingly interested in studying functional traits to better understand how terrestrial plants allocate their resources. This led to a prominent ecological theory: the ‘fast-slow’ plant economics spectrum, which describes a universal spectrum of plant economics comprising key plant properties. The spectrum runs from fast-growing species with traits associated to rapid resource acquisition to slow-growing species having traits involved in conservation of resources and investing more resources in anti-herbivore defenses. Although major nutrients have been included in the spectrum, the concentration of silicon (Si) in plant tissues has long been ignored, a significant omission given that vascular plants contain Si in widely variable concentrations, in some cases far exceeding those of macronutrients. Most previous ecological studies have considered Si as an anti-herbivore defense and structural component, which can substitute for carbon-based defense compounds, rather than integral to other aspects of plant eco-physiological strategies. The aim of SiliConomic is to leverage functional trait-based approaches to build an eco-physiological understanding of the role of Si in terrestrial ecosystems and determine its position in the plant economics spectrum. To do so, key characteristics of plant eco-physiological/defense strategies will be measured in Mediterranean shrubland/rangeland ecosystems along a unique long-term natural soil fertility gradient spanning two million years of ecosystem development, and a long-term fertilization/grazing experiment. A plant growth experiment under controlled conditions will be conducted to develop a mechanistic understanding of underlying processes. The project represents the first attempt to integrate Si in the plant economics spectrum, is based on exceptional environmental gradients and collaboration with world-leading researchers, and is of global interest in plant ecology.