Effects of Vegetation Restoration Age on Soil C: N: P Stoichiometry in Yellow River Delta Coastal Wetland of China

Vegetation restoration can alter carbon (C), nitrogen (N), and phosphorus (P) cycles in coastal wetlands affecting C: N: P stoichiometry. However, the effects of restoration age on soil C: N: P stoichiometry are unclear. In this study, we examined the responses of soil C, N, and P contents and their stoichiometric ratios to vegetation restoration age, focusing on below-ground processes and their relationships to aboveground vegetation community characteristics. We conducted an analysis of temporal gradients based on the ‘space for time’ method to synthesize the effects of restoration age on soil C: N: P stoichiometry in the Yellow River Delta wetland of China. The findings suggest that the combined effects of restoration age and soil depth create complex patterns of shifting soil C: N: P stoichiometry. Specifically, restoration age significantly increased all topsoil C: N: P stoichiometries, except for soil total phosphorus (TP) and the C: N ratio, and slightly affected subsoil C: N: P stoichiometry. The effects of restoration age on the soil C: N ratio was well constrained owing to the coupled relationship between soil organic carbon (SOC) and total nitrogen (TN) contents, while soil TP content was closely related to changes in plant species diversity. Importantly, we found that the topsoil C: N: P stoichiometry was significantly affected by plant species diversity, whereas the subsoil C: N: P stoichiometry was more easily regulated by pH and electric conductivity (EC). Overall, this study shows that vegetation restoration age elevated SOC and N contents and alleviated N limitation, which is useful for further assessing soil C: N: P stoichiometry in coastal restoration wetlands.