Temporal variation of soil phosphorus fractions and nutrient stoichiometry during wetland restoration: Implications...

Wetland restoration can promote the recovery of ecosystem services. However, an increasing number of reports indicate that phosphorus leaching risk occurs in downstream water bodies during the early stages of agricultural utilized wetland restoration, it is unclear that whether this phenomenon depend on temporal dynamics. Therefore, in this study, we used soil phosphorus fractions and stoichiometry as indicators to investigate soil phosphorus leaching and examine their evolution during both short- and long-term wetland restoration, aiming to identify the key driving factors. The results showed that only soil inorganic phosphorus (Pi) decreased during short-term restoration, while soil organic P (Po) increased during long-term restoration, which indicates that the restoration period can promote the transformation of Pi to Po. The soil total organic carbon: total P (C:P) and total nitrogen: total P (N:P) ratios did not differ during short-term wetland restoration, while C:P and N:P significantly increased under long-term wetland restoration (163% and 225%), demonstrating an increasing trend of P demand with increasing wetland restoration time. Finally, redundancy analysis showed that reactive iron (Fe_r) and pH were the dominant factors influencing soil P pools under short-term restoration. In contrast, TN, SOC, and pH were dominant factors driving P pools under long-term restoration, and changes in the dominant factors driving P pools also implied that organic carbon contributed to Po accumulation. Overall, these indicators show that wetland restoration improves soil P stability and reduces the potential for soil P release. The findings highlight the importance of incorporating soil P fraction analyses and stoichiometric evaluation into P management during wetland restorations.