Freeze-thaw cycles increase the mobility of phosphorus fractions based on soil aggregate in restored wetlands

Available information about the effects of freeze–thaw cycles (FTCs) and soil aggregate structure on the mobility of phosphorus (P) fractions is limited. Here, soil column experiments with different initial moisture contents (saturated moisture content and field capacity) were used to study the redistribution of P fractions in soil aggregates after 0, 2, 5, and 10 freeze–thaw cycles. The results showed that FTCs decrease the stability of soil aggregates, leading to the loss of carbon and nitrogen. FTCs increase the mobility of phosphorus fractions based on soil aggregate in restored wetlands. Soil with saturated moisture content can promote the transformation of available P to moderately available P, resulting in reduced risk of P mobility after FTCs. Redundancy analysis showed that total nitrogen and soil bacteria diversity are critical factors explaining 69.5% of the observed changes in P fractions. Our results are of great significance for studying the P supply capacity and reducing the potential release of P in restored wetlands.