Abstract: Phosphorus is one of the key nutrients that limit plant productivity. In deserts, phosphorus is particularly crucial given its deficiency in soil. Groundwater is one of the significant factors affecting soil phosphorus content in deserts. However, the variations of soil phosphorus fractions at different groundwater depths remain poorly understood. In this study, changes in soil phosphorus fractions at three groundwater depths (2.5, 4.5, and 11.0 m) were characterized using the Hedley phosphorus classification method. The results showed that the concentrations of active phosphorus (sodium bicarbonate-extractable inorganic phosphorus, sodium bicarbonate-extractable organic phosphorus), insoluble phosphorus (diluted hydrochloric acid-extractable phosphorus, concentrated hydrochloric acid-extractable inorganic phosphorus, concentrated hydrochloric acid-extractable organic phosphorus, residual phosphorus), and sodium hydroxide-extractable inorganic phosphorus at the groundwater depth of 11.0 m were significantly greater than those at the groundwater depths of 2.5 m and 4.5 m. However, sodium hydroxide organic phosphorus and resin phosphorus showed no variation. Soil microbial biomass phosphorus at 2.5 m depth was significantly lower than those at 4.5 and 11.0 m, microbial biomass carbon was significantly lower at 4.5 m compared to 11.0 m, and microbial biomass nitrogen  did not vary among the depths (P<0.05). Redundancy analysis revealed that groundwater depth was a key environmental factor influencing the variations in soil phosphorus fractions. This study provides a scientific basis for understanding the response of soil phosphorus fractions in deserts to varying groundwater depths and offers a theoretical foundation for the recovery and conservation of desert plants.

Key words: Hedley phosphorus classification method, desert, phosphorus fraction, groundwater depth, soil microorganism