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 Plants retain and accumulate silicon when soil reserves are depleted, thereby sustaining silicon cycling. 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.

中文翻译：

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植物在生态系统退化期间维持陆地硅循环

硅的陆地生物地球化学硅是植物组织中的重要元素，有助于抵御食草动物和其他压力的结构防御。然而，人们对硅的陆地生物地球化学循环知之甚少，尤其是地球化学和生物机制在其调控中的相对重要性。德汤伯等人。在西澳大利亚州土壤和植被的 200 万年时间序列中研究了这个问题。随着年龄的增长，遗址变得越来越风化和贫瘠，这表明随着生态系统的发展，硅循环从地球化学转变为生物控制（参见凯里的观点）。他们发现，在生态系统发展过程中，叶面硅浓度不断增加，即使岩石衍生的硅在较旧的土壤中已经耗尽。相比之下，其他主要来自岩石的养分在植物中的浓度呈下降趋势。因此，生物硅循环使植物即使在极端土壤贫瘠的条件下也能保持浓度。科学，这个问题 p。1245; 另见第 1161 当土壤储量耗尽时，植物会保留和积累硅，从而维持硅循环。生物地球化学硅循环影响全球初级生产力和碳循环，但对陆地生态系统长期发展过程中硅来源和循环的变化仍知之甚少。在这里，我们展示了在西澳大利亚 200 万年土壤时间序列的长期生态系统发展过程中，陆地硅循环从土壤控制转变为生物控制。硅的可用性取决于年轻土壤中的成土硅和旧土壤中植物来源的硅在成土池枯竭时的回收利用。与在强风化土壤中显着下降的主要养分浓度不同，叶面硅浓度随着土壤老化而不断增加。我们的研究结果表明，在生态系统退化期间植物对硅的保留维持了其陆地循环，这表明在营养贫乏的环境中与该元素相关的重要植物益处。