The leaching of P from the upper 20 cm of forest topsoils influences nutrient (re-)cycling and the redistribution of available phosphate and organic P forms. However, the effective leaching of colloids and associated P forms from forest topsoils was so far sparsely investigated. We demonstrated through irrigation experiments with undisturbed mesocosm soil columns, that significant proportions of P leached from acidic forest topsoils were associated with natural colloids. These colloids had a maximum size of 400 nm. By means of Field-flow fractionation the leached soil colloids could be separated into three size fractions. The size and composition was comparable to colloids present in acidic forest streams known from literature. The composition of leached colloids of the three size classes was dominated by organic carbon. Furthermore, these colloids contained large concentrations of P which amounted between 12 and 91% of the totally leached P depending on the type of the forest soil. The fraction of other elements leached with colloids ranged between 1% and 25% (Fe: 1–25%; C_org: 3–17%; Al: <4%; Si, Ca, Mn: all <2%). The proportion of colloid–associated P decreased with increasing total P leaching. Leaching of total and colloid-associated P from the forest surface soil did not increase with increasing bulk soil P concentrations and were also not related to tree species. The present study highlighted that colloid-facilitated P leaching can be of higher relevance for the P leaching from forest surface soils than dissolved P and should not be neglected in soil water flux studies.

从森林表层土壤的上部20 cm浸出的P会影响养分的（再）循环以及可利用的磷酸盐和有机P形态的重新分布。然而，迄今为止，对从森林表层土壤中有效浸出胶体和相关磷形式的研究还很少。我们通过未经扰动的中观土壤柱的灌溉实验证明，从酸性森林表层土壤中浸出的大量P与天然胶体有关。这些胶体的最大尺寸为400nm。通过场流分级分离，可以将沥滤的土壤胶体分为三个大小部分。其大小和组成与文献中已知的酸性森林溪流中存在的胶体相当。三种尺寸类别的浸出胶体的组成以有机碳为主。此外，这些胶体含有高浓度的磷，取决于森林土壤的类型，其含量占总浸出磷的12％至91％。胶体浸出的其他元素的比例在1％到25％之间（Fe：1-25％； C_组织：3–17％；铝：<4％；Si，Ca，Mn：全部<2％）。胶体相关磷的比例随着总磷浸出的增加而降低。从森林表层土壤中浸出的总磷和胶体相关磷并没有随散装土壤磷含量的增加而增加，并且也与树种无关。本研究强调，胶体促进的P淋溶与森林表层土壤中P淋溶的相关性高于溶解性P，在土壤水通量研究中不应忽略。