Abstract Dissolved and colloidal phosphorus (P) represent the mobile P fractions in soils, but their role in P cycling in forests is still largely unclear. In this study of four calcareous forest soil profiles, the elemental compositions of different size fractions of water dispersible colloids (WDC) were investigated by asymmetric field flow fractionation. Nuclear magnetic resonance spectroscopy (NMR) was applied to identify the organic P compounds in soils, WDC, and soil solutions. Carbon was the dominant element in WDC of all soil horizons, including mineral soils that were rich in Ca or Si. Although chemical composition of P varied dramatically with increasing depth, the colloidal P composition remained unchanged. This contrasting difference between mineral soil and its WDC fraction indicated that the colloids were not locally generated but originated from the overlying organic soil horizons. Carbonate minerals were unlikely involved in colloid formation under acidic condition. Instead, Ca2+ probably drove colloid formation by bridging organic matter, including P-containing compounds released from litter degradation. Colloid formation was influenced by climate, vegetation, and soil characteristics. No dissolved P was detected in deeper mineral soil horizons due to efficient retention by Ca minerals. Colloidal P was still present in deeper soil layers and thus of significance for potential P vertical transfer.

中文翻译：

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溶解磷和胶体磷对钙质森林土壤磷循环的影响

摘要 溶解磷和胶体磷 (P) 代表土壤中可移动的磷组分，但它们在森林磷循环中的作用仍不清楚。在这项对四种钙质森林土壤剖面的研究中，通过不对称场流分馏研究了不同尺寸级分的水分散胶体 (WDC) 的元素组成。应用核磁共振波谱 (NMR) 来鉴定土壤、WDC 和土壤溶液中的有机 P 化合物。碳是所有土壤层的 WDC 中的主要元素，包括富含 Ca 或 Si 的矿质土壤。尽管 P 的化学成分随着深度的增加而显着变化，但胶体 P 的成分保持不变。矿质土壤与其 WDC 部分之间的这种对比差异表明胶体不是局部产生的，而是源自上覆的有机土壤层。在酸性条件下，碳酸盐矿物不太可能参与胶体的形成。相反，Ca2+ 可能通过桥接有机物质（包括垃圾降解释放的含磷化合物）来推动胶体的形成。胶体的形成受气候、植被和土壤特征的影响。由于钙矿物质的有效保留，在更深的矿质土壤层中没有检测到溶解的磷。胶体磷仍然存在于较深的土壤层中，因此对潜在的磷垂直转移具有重要意义。Ca2+ 可能通过桥接有机物质（包括垃圾降解释放的含磷化合物）来推动胶体的形成。胶体的形成受气候、植被和土壤特征的影响。由于钙矿物质的有效保留，在更深的矿质土壤层中没有检测到溶解的磷。胶体磷仍然存在于较深的土壤层中，因此对潜在的磷垂直转移具有重要意义。Ca2+ 可能通过桥接有机物质（包括垃圾降解释放的含磷化合物）来推动胶体的形成。胶体的形成受气候、植被和土壤特征的影响。由于钙矿物质的有效保留，在更深的矿质土壤层中没有检测到溶解的磷。胶体磷仍然存在于较深的土壤层中，因此对潜在的磷垂直转移具有重要意义。