Objective The aims were to understand the distribution characteristics of phosphorus (P) content in the Mu Us Sandy Land, and to clarify the influence of wetland degradation on the morphological characteristics of soil P.

Method four regions of un-degraded (UD), mildly degraded (LD), moderately degraded (MD), and severely degraded (SD) of two wetlands in the Tuwei River Basin of Mu Us Sandy Land were studied. The Hedley P grading method was used to measure and compare the differences in soil P form contents under different degrees of degradation, and to elucidate the environmental factors affecting soil P forms in degraded wetlands in arid areas.

Result ① The overall soil P level in the degraded wetland of Mu Us Sandy Land was low, with inorganic P accounting for 51.35% - 79.57%, and the proportion of inorganic P showed an increasing trend with the intensification of degradation. ② As the degree of degradation intensifies, the overall content of various P forms showed a downward trend, while the contents of H₂O-P and NaHCO₃-P were at a relatively low level, only 1.71 - 8.19 mg kg⁻¹, and showed a downward trend as degradation intensifies. The proportion of HCl-Pi in soil inorganic P components and Residual-P in soil organic P components was the highest (> 50%), and the contents changed most significantly with the intensification of degradation. ③ Soil organic matter and total nitrogen had a high correlation with various forms of P, especially with H₂O-P, NaHCO₃-Pi, and NaOH-Pi, with a correlation coefficient of over 0.90.

Conclusion All P forms in the soil show varying degrees of decrease with the intensification of wetland degradation, with the most significant decrease in soil organic P. The research results are expected to provide scientific basis for the maintenance of wetland soil nutrients and the restoration management of sandy land in the Mu Us Sandy land in the future.