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2748

21 décembre 2020 16:18

21 décembre 2020 16:18

Terrestrial biogeochemistry of silicon Silicon is an important element in plant tissues and contributes to structural defenses against herbivores and other stresses. However, the terrestrial biogeochemical cycling of silicon is poorly understood, particularly the relative importance of geochemical and biological mechanisms in its regulation. de Tombeur et al. studied this question in 2-million-year chronosequences of soil and vegetation in Western Australia. Sites became progressively more weathered and infertile as they aged, indicating that the silicon cycle shifts from geochemical to biological control as the ecosystem develops (see the Perspective by Carey). They found that foliar silicon concentrations increase continuously during ecosystem development, even though rock-derived silicon is depleted in the older soils. By contrast, other major rock-derived nutrients showed decreasing concentrations in plants. Hence, biological silicon cycling allows plants to maintain concentrations even under conditions of extreme soil infertility. Science, this issue p. 1245; see also p. 1161 The biogeochemical silicon cycle influences global primary productivity and carbon cycling, yet changes in silicon sources and cycling during long-term development of terrestrial ecosystems remain poorly understood. Here, we show that terrestrial silicon cycling shifts from pedological to biological control during long-term ecosystem development along 2-million-year soil chronosequences in Western Australia. Silicon availability is determined by pedogenic silicon in young soils and recycling of plant-derived silicon in old soils as pedogenic pools become depleted. Unlike concentrations of major nutrients, which decline markedly in strongly weathered soils, foliar silicon concentrations increase continuously as soils age. Our findings show that the retention of silicon by plants during ecosystem retrogression sustains its terrestrial cycling, suggesting important plant benefits associated with this element in nutrient-poor environments. Plants retain and accumulate silicon when soil reserves are depleted, thereby sustaining silicon cycling. Plants retain and accumulate silicon when soil reserves are depleted, thereby sustaining silicon cycling.

None

• AB - Non-spécifique
• FREDO biologie et travail du sol
• FREDO santé végétale
• GEO Australie
• silicon

Science

369

1245-1248

2020/09/04

4 septembre 2020

10.1126/science.abc0393 Le DOI est une URL unique de référencement d'une publication. Il est donc plus fiable et permanent qu'une URL classique

0036-8075, 1095-9203 L’ISSN est un code de 8 chiffres servant à identifier les journaux, revues, magazines, périodiques de toute nature et sur tous supports, papier comme électronique.