Recent studies demonstrate a strong influence of soil age on long-term silicon (Si) dynamics in terrestrial ecosystems, but how variation in ecosystem water balance and soil parent material impact this trajectory is unknown. We addressed this by studying a 2-million-year dune chronosequence in southwestern Australia characterized by a positive water balance (+ 50 mm year⁻¹) and a lower carbonate concentration in the parent sand (5%) compared with two chronosequences already characterized (− 900 and − 750 mm year⁻¹; 88 and 74%). We sampled soils from the progressive and retrogressive phases of ecosystem development to quantify pedogenic reactive Si (extracted in ammonium oxalate and oxalic acid), phytoliths (biogenic Si), and plant-available Si (extracted in dilute CaCl₂). Silicon mobilization was buffered by carbonate in the early stages of the two carbonate-rich drier chronosequences, as previously highlighted, but not in the carbonate-poor wetter chronosequence. Reactive pedogenic Si and plant-available Si did not peak at intermediate stages in the carbonate-poor wetter chronosequence, where almost no clay formation occurred, as it did in the carbonate-rich drier chronosequences during clay formation after carbonate loss. This is probably due to a combination of lower content of weatherable minerals in the soil parent material and higher weathering rates. Phytolith stocks were similar across the three chronosequences, suggesting that a climate-driven increase in biomass and associated phytolith production in wetter sites counterbalance the higher phytolith dissolution rates and physical translocation. Together, these results demonstrate that the initial carbonate concentration in the soil parent material and subsequent mineralogical evolution drive long-term soil Si dynamics, and suggest a significant influence of climate-induced variation in biomass production on the Si biological feedback loop, even in old and highly desilicated environments.

最近的研究表明，土壤年龄对陆地生态系统中的长期硅 (Si) 动态有很大影响，但生态系统水平衡和土壤母体材料的变化如何影响这一轨迹尚不清楚。我们通过研究澳大利亚西南部一个长达 200 万年的沙丘时间序列来解决这个问题，与已经表征的两个时间序列相比，该序列具有正的水平衡（+ 50 mm 年^-1）和母砂中较低的碳酸盐浓度（5%）（ − 900 和 − 750 mm 年⁻¹；88% 和 74%)。我们从生态系统发展的渐进和退化阶段对土壤进行采样，以量化土壤活性硅（从草酸铵和草酸中提取）、植硅体（生物硅）和植物可利用硅（在稀释的 CaCl _{2 中}提取））。如前所述，在两个富含碳酸盐的干燥时间序列的早期阶段，硅的流动被碳酸盐缓冲，但在缺乏碳酸盐的湿润时间序列中则不然。活性成土硅和植物可利用硅在碳酸盐含量低的湿润年代序列的中间阶段没有达到峰值，几乎没有粘土形成，就像在碳酸盐流失后粘土形成期间富含碳酸盐的干燥年代序列中那样。这可能是由于土壤母质中耐候矿物质含量较低和风化率较高的综合作用。三个时间序列的植硅体储量相似，这表明气候驱动的生物量增加和湿润地区相关植硅体产量的增加抵消了较高的植硅体溶解率和物理易位。一起，