At the earliest stage of pedogenesis, microorganisms are the main biological drivers of nutrient transformation and mobilization from rock minerals. However, this driving process is not yet well understood despite its importance for the formation and fertility of soil. The aim of this study was to determine the microbial accumulation of organic phosphorus (Po) and microbial release of bioavailable phosphorus (bio-P) from rock minerals and to analyse which factors control these processes. We hypothesized that microorganisms contribute to stabilization and accumulation of Po. For this purpose, we carried out a series of incubation experiments with model soils (with soil Po removed) and soil extracts of natural soil from the earliest stage of pedogenesis in the newest retreat area of the Hailuogou glacier. A modified Hedley fractionation method was used to characterize the P forms in soils. Microbial synthesis of Po was clearly observed in this study. In view of the fact that carbon (C) and nitrogen (N) are the main energy and material sources of microorganisms and that their stoichiometry plays an important role in microbial metabolism, we hypothesized that the C and N (ratio and level) play a regulatory role in microbial transformation of P. Therefore, the different C/N gradients were constructed in our incubation experiments. Results showed addition of C and N resulted in an accumulation of stable Po and decrease in pH in soils. These results suggest that not all microbial biomass P is easily degraded. Along two C/N ratio gradients (same ratio but keeping C vs N constant), opposite patterns of total Po (TPo) changes was observed. Opposite patterns were also observed for bio-P along the two C/N ratio gradients. Regardless of the C/N ratio, high CN additions always led to lower TPo accumulations, higher bio-P releases and higher phosphatase activity compared to low CN additions. We conclude that microbial synthesis of Po contributed to the P fractions in soil stable residual pools and that microbial release of bioavailable P was driven by two modes (i.e., N-driven mode and C-driven mode). Our study highlights that microorganisms drive the accumulation of soil Po during the earliest stage of pedogenesis in our study area.

在成土作用的最早阶段，微生物是岩石矿物养分转化和动员的主要生物学驱动力。然而，尽管它对土壤的形成和肥力很重要，但这种驱动过程尚未得到很好的理解。本研究的目的是确定岩石矿物中有机磷 (Po) 的微生物积累和生物有效磷 (bio-P) 的微生物释放，并分析哪些因素控制这些过程。我们假设微生物有助于 Po 的稳定和积累。为此，我们在海螺沟冰川最新退缩区，对模型土壤（去除土壤Po）和天然土壤最早阶段的土壤提取物进行了一系列孵化实验。改进的 Hedley 分级方法用于表征土壤中的 P 形式。在这项研究中清楚地观察到 Po 的微生物合成。鉴于碳（C）和氮（N）是微生物的主要能量和物质来源，并且它们的化学计量在微生物代谢中起着重要作用，我们假设C和N（比率和水平）起P的微生物转化中的调节作用。因此，在我们的孵化实验中构建了不同的C / N梯度。结果表明，添加 C 和 N 导致土壤中稳定的 Po 积累和 pH 值降低。这些结果表明，并非所有微生物量 P 都容易降解。沿着两个 C/N 比率梯度（相同比率但保持 C 与 N 恒定），观察到相反的总 Po (TPo) 变化模式。沿两个 C/N 比梯度的 bio-P 也观察到相反的模式。无论 C/N 比如何，与低 CN 添加相比，高 CN 添加总是导致较低的 TPo 积累、更高的 bio-P 释放和更高的磷酸酶活性。我们得出结论，Po 的微生物合成有助于土壤稳定残留池中的 P 部分，并且生物可利用 P 的微生物释放受两种模式（即 N 驱动模式和 C 驱动模式）驱动。我们的研究强调，在我们研究区域的成土发生的最早阶段，微生物驱动了土壤 Po 的积累。我们得出结论，Po 的微生物合成有助于土壤稳定残留池中的 P 部分，并且生物可利用 P 的微生物释放受两种模式（即 N 驱动模式和 C 驱动模式）驱动。我们的研究强调，在我们研究区域的成土发生的最早阶段，微生物驱动了土壤 Po 的积累。我们得出结论，Po 的微生物合成有助于土壤稳定残留池中的 P 部分，并且生物可利用 P 的微生物释放受两种模式（即 N 驱动模式和 C 驱动模式）驱动。我们的研究强调，在我们研究区域的成土发生的最早阶段，微生物驱动了土壤 Po 的积累。