Phosphorus (P) is one of the limiting nutrients in Inner Mongolia steppe soil, which seriously affect steppe productivity. Therefore, it is necessary to understand the distribution characteristics of organic P (Po) fractions and their influencing factors in Inner Mongolia steppe soil and to identify the contribution of Po fractions to soil available P (AP) to maintain the sustainable development of the Inner Mongolia steppe by improving the utilization rate of Po. The contents of soil Po fractions such as H2O-extractable Po (H2O-Po), NaHCO3-extractable Po (NaHCO3-Po), HCl-extractable Po (HCl-Po), NaOH-extractable Po (NaOH-Po), and phytate P (Phyt-P) were determined in soil samples (0–15 cm) from 15 sampling sites representing three types of grassland (i.e., desert steppe, typical steppe, and meadow steppe) in Inner Mongolia. The influencing factors of the soil Po fractions were determined by redundancy analysis (RDA). Soil Po content accounted for 61.0% of the total P (TP) on average. NaOH-Po was the main fraction of Po, accounting for 49.1% of Po on average; H2O-Po content accounted for the least amount of Po (mean 1.3 mg kg−1). H2O-Po and HCl-Po were not significantly different among the three steppes. The contents of NaHCO3-Po increased in the order of desert steppe < typical steppe < meadow steppe, and the trend of NaOH-Po and Phyt-P contents were desert steppe < meadow steppe < typical steppe. Pearson correlation analysis showed that NaHCO3-Po was positively correlated with AP (r = 0.86, p < 0.01). HCl-Po was negatively correlated with AP (r = − 0.56, p < 0.05). NaOH-Po and Phyt-P were significantly positively correlated with NaHCO3-extractable inorganic P (NaHCO3-Pi); Phyt-P was also negatively correlated with HCl-extractable Pi (HCl-Pi) (r = − 0.61, p < 0.05). These correlations were mainly caused by differences in steppe types and soil properties caused by climatic conditions, as shown by the result of RDA analysis. Soil Po plays an indispensable role in the supply of soil P in the semi-arid steppe of Inner Mongolia, where NaHCO3-Po and HCl-Po strongly contributed to AP. In addition, NaOH-Po and Phyt-P as a part of stable pools are important for providing P to other P pools. Po fractions in steppe soils were mainly regulated by climatic conditions and are closely related to the soil organic matter and pH.

中文翻译：

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内蒙古草原土壤有机磷组分分布特征

磷（P）是内蒙古草原土壤中的限制性养分之一，严重影响草原生产力。因此，有必要了解内蒙古草原土壤有机磷（Po）组分的分布特征及其影响因素，确定有机磷组分对土壤有效磷（AP）的贡献，以维持内蒙古草原的可持续发展。草原通过提高坡的利用率。土壤 Po 组分的含量，如 H2O-可提取的 Po (H2O-Po)、NaHCO3-可提取的 Po (NaHCO3-Po)、HCl-可提取的 Po (HCl-Po)、NaOH-可提取的 Po (NaOH-Po) 和植酸盐P (Phyt-P) 在来自代表内蒙古三种草原（即沙漠草原、典型草原和草甸草原）的 15 个采样点的土壤样品（0-15 cm）中测定。通过冗余分析(RDA)确定土壤Po组分的影响因素。土壤磷含量平均占总磷（TP）的61.0%。NaOH-Po是Po的主要组分，平均占Po的49.1%；H2O-Po 含量占 Po 含量最少（平均 1.3 mg kg-1）。H2O-Po 和 HCl-Po 在三个草原之间没有显着差异。NaHCO3-Po含量按荒漠草原<典型草原<草甸草原的顺序增加，NaOH-Po和Phyt-P含量的变化趋势为荒漠草原<草甸草原<典型草原。Pearson 相关分析表明 NaHCO3-Po 与 AP 呈正相关（r = 0.86，p < 0.01）。HCl-Po 与 AP 呈负相关（r = - 0.56，p < 0.05）。NaOH-Po和Phyt-P与NaHCO3可萃取无机P（NaHCO3-Pi）呈显着正相关；Phyt-P 也与 HCl 可提取的 Pi (HCl-Pi) 呈负相关（r = - 0.61，p < 0.05）。这些相关性主要是由气候条件引起的草原类型和土壤性质的差异引起的，如 RDA 分析的结果所示。内蒙古半干旱草原土壤磷在土壤磷的供给中起着不可或缺的作用，其中NaHCO3-Po和HCl-Po对AP的贡献很大。此外，NaOH-Po 和 Phyt-P 作为稳定池的一部分对于向其他 P 池提供 P 很重要。草原土壤中的 Po 组分主要受气候条件的调控，与土壤有机质和 pH 值密切相关。Phyt-P 也与 HCl 可提取的 Pi (HCl-Pi) 呈负相关（r = - 0.61，p < 0.05）。这些相关性主要是由气候条件引起的草原类型和土壤性质的差异引起的，如 RDA 分析的结果所示。内蒙古半干旱草原土壤磷在土壤磷的供给中起着不可或缺的作用，其中NaHCO3-Po和HCl-Po对AP的贡献很大。此外，NaOH-Po 和 Phyt-P 作为稳定池的一部分对于向其他 P 池提供 P 很重要。草原土壤中的 Po 组分主要受气候条件的调节，与土壤有机质和 pH 值密切相关。Phyt-P 也与 HCl 可提取的 Pi (HCl-Pi) 呈负相关（r = - 0.61，p < 0.05）。这些相关性主要是由气候条件引起的草原类型和土壤性质的差异引起的，如 RDA 分析的结果所示。内蒙古半干旱草原土壤磷在土壤磷的供给中起着不可或缺的作用，其中NaHCO3-Po和HCl-Po对AP的贡献很大。此外，NaOH-Po 和 Phyt-P 作为稳定池的一部分对于向其他 P 池提供 P 很重要。草原土壤中的 Po 组分主要受气候条件的调控，与土壤有机质和 pH 值密切相关。内蒙古半干旱草原土壤磷在土壤磷的供给中起着不可或缺的作用，其中NaHCO3-Po和HCl-Po对AP的贡献很大。此外，NaOH-Po 和 Phyt-P 作为稳定池的一部分对于向其他 P 池提供 P 很重要。草原土壤中的 Po 组分主要受气候条件的调控，与土壤有机质和 pH 值密切相关。内蒙古半干旱草原土壤磷在土壤磷的供给中起着不可或缺的作用，其中NaHCO3-Po和HCl-Po对AP的贡献很大。此外，NaOH-Po 和 Phyt-P 作为稳定池的一部分对于向其他 P 池提供 P 很重要。草原土壤中的 Po 组分主要受气候条件的调控，与土壤有机质和 pH 值密切相关。