Effects of different restoration methods on soil aggregate phosphorus availability and fractions in alpine mine slopes

The deficiency of soil phosphorus (P) resources is a challenge of worldwide concern. The efficiency of soil P utilization in alpine mine slopes is especially poor, which limits the growth of plants, making slopes difficult to restore and causing frequent natural disasters. In this study, three mine slopes were chosen as representative study sites on China's Qinghai-Tibet Plateau, and the soil aggregate P fractions' distribution and changes under frame beam restoration slope (FRS), metal wire mesh restoration slope (MRS), and natural slope (NS) were investigated, as well as the mechanisms relating P fractions to P availability. The results demonstrated that soil aggregate P availability and fractions in alpine mine slopes were significantly impacted by various restoration methods. In soil aggregates of both FRS and MRS, TP and AP contents were lower than NS, and showing a trend of FRS>MRS. The P activation coefficients were almost all < 2 % in the soil aggregates of three slopes, indicating that TP was difficult to convert to AP. In all three slopes, the total inorganic P contents of soil aggregates with varying particle sizes were NS > FRS > MRS. Classifying the P fractions by stability, the soil P fractions contents generally showed that active P < moderately active P < stable P, and soil aggregates with different particle sizes in FRS had substantially greater active P contents than those in MRS. Additionally, H₂O-Pi and DHCl-Pi showed significant direct negative effects on AP, with path coefficients of −0.24 and −0.30 respectively. The physicochemical factors pH and SOM, which mainly drove changes in soil P fractions, also differed because they were affected by different restoration methods. This study will be dedicated to providing a theoretical framework for managing soil P in alpine mine slopes during the ecological restoration process and providing reference opinions for the selection of restoration techniques for alpine mines.