The amount of water available to leach solutes from soil is one of the major features determining mineral weathering, mineral neoformation and soil properties. It affects the fate of dissolved silicon (Si), which may follow four routes: leaching, mineral synthesis, adsorption, uptake by plants forming phytoliths. Here, we quantify the reservoirs of bioavailable Si and phytolithic Si in topsoils (0–20 cm) from wet tropical Andosols along a climosequence where mean annual rainfall (MAR) increases from 2650 to 4400 mm with increasing altitude (65–375 m asl) in Basse-Terre, Guadeloupe. We assessed bioavailable Si through CaCl₂ extraction in soil, and foliar analysis in banana plants. We evaluated the pool of phytolithic Si through Na₂CO₃ extraction and heavy liquid separation. The Na₂CO₃ extraction was performed on both the bulk soil and oxalate–treated soil (ox-Na₂CO₃) cleared of its amorphous aluminosilicates. The Andosols have reached an advanced weathering stage. Their secondary products included (Al, Fe)–humus complexes, ferrihydrite, gibbsite, poorly crystalline Al hydroxide, and aluminous allophanic substances. The contents of organic C, metal-humus, ferrihydrite and gibbsite increased in soils in the wettest conditions (>3000 mm) whereas allophane content concomitantly decreased. Silicon leaf content varied little (3.8–5.3 g kg⁻¹), but slightly decreased with increasing MAR (r = −0.48). Bioavailable Si content in soil decreased from 63 to 12 mg kg⁻¹ with increasing MAR (r = −0.92), and was strongly correlated (r = +0.95) to that of phytolithic Si as assessed after ox-Na₂CO₃ extraction, linked to fresh, labile phytoliths. The Si/Al atomic ratio of the ox-Na₂CO₃ extract regularly decreased from 1.06 to 0.37 with increasing MAR, hence corroborating strongest desilication in soils in the wettest conditions. In these highly leached, gibbsitic Andosols, rainfall is thus the major driver of plant Si availability.

可用于从土壤中浸出溶质的水量是决定矿物风化、矿物新形成和土壤性质的主要特征之一。它影响溶解硅 (Si) 的命运，可能遵循四种途径：浸出、矿物合成、吸附、植物吸收形成植硅体。在这里，我们量化了来自潮湿热带安多溶胶的表土（0-20 厘米）中的生物可利用硅和植石硅的储量，沿着气候序列，其中年均降雨量 (MAR) 随着海拔升高 (65-375 米 asl) 从 2650 毫米增加到 4400 毫米位于瓜德罗普岛的 Basse-Terre。我们通过土壤中的CaCl ₂提取和香蕉植物的叶面分析评估了生物可利用的硅。我们通过 Na ₂ CO ₃评估了植石 Si 池萃取和重液分离。Na ₂ CO ₃提取在大块土壤和草酸盐处理的土壤（ox-Na ₂ CO ₃）上进行，去除了其无定形硅铝酸盐。Andosols 已达到高级风化阶段。他们的副产品包括 (Al, Fe)-腐殖质复合物、水铁矿、三水铝石、结晶性差的氢氧化铝和铝基磷灰石物质。在最潮湿条件下（>3000 毫米），土壤中有机碳、金属腐殖质、水铁矿和三水铝石的含量增加，而水铝石含量随之下降。硅叶含量变化不大（3.8-5.3 g kg ^-1)，但随着 MAR 的增加而略有下降 (r = -0.48)。随着 MAR (r = -0.92) 的增加，土壤中的生物可利用 Si 含量从 63 降至 12 mg kg ^-1，并且与 ox-Na ₂ CO ₃提取后评估的植石 Si 的含量密切相关 (r = +0.95) ，与新鲜、不稳定的植硅体有关。随着 MAR 的增加，ox-Na ₂ CO ₃提取物的 Si/Al 原子比有规律地从 1.06 下降到 0.37，因此证实了最潮湿条件下土壤中最强的脱硅作用。因此，在这些高度浸出的三水铝石安多溶胶中，降雨是植物硅可用性的主要驱动因素。