Soil C, N, P, and Si stoichiometric characteristics, drivers and relationship with vegetation productivity in coastal wetlands in China

The investigation of soil stoichiometry characteristics, spatial patterns and driving factors in coastal wetlands is of great significance in revealing soil nutrient cycling in coastal wetlands and elucidating their response mechanisms to environmental changes. This study analyzed the elemental contents and stoichiometric characteristics of carbon (C), nitrogen (N), phosphorus (P), and silicon (Si) in the coastal wetlands soils in China, exploring their variations and driving mechanisms at a large spatial scale. By examining relationship between soil stoichiometric ratios and net primary productivity (NPP), the study revealed the interaction between soil nutrients and vegetation productivity in coastal wetlands. The results showed that the contents of soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), and available silicon (ASi) in coastal wetlands were (11.43±0.76) g/kg, (0.96±0.05) g/kg, (0.58±0.01) g/kg, and (0.03±0.001) g/kg, respectively. Soil C:N, C:P, C:Si, N:P, N:Si, and Si:P were 11.44±0.36, 22.28±2.10, 366.32±18.18, 1.76±0.10, 33.13±1.52 and 0.06±0.001, respectively. The growth of wetland soils and vegetation was mainly under N limitation. Soil stoichiometric characteristics showed a decreasing trend with increasing soil depth, which may be influenced by surface vegetation and active environmental factors. Mean annual temperature (MAT) and mean annual precipitation (MAP) were identified as key drivers of the quadratic distribution patterns of soil stoichiometric characteristics along latitudinal gradients. The coastal wetlands in southern China had higher C:N, C:P, and N:P, indicating that the rate of SOC mineralization, the availability of soil N and P, and the degree of soil N limitation were lower than those in the northern region. pH was the most important factor affecting the stoichiometric characteristics of coastal wetland soils in China, followed by soil electrical conductivity (EC), specific surface area (SSA), and particle size composition. In coastal wetlands, soil C:P and N:P ratios significantly increased with rising NPP (p<0.05). The NPP of salt marshes was primarily influenced by soil Si:P, while mangrove NPP was predominantly regulated by soil C:P. This research contributes valuable insights into the soil characteristics of China’s coastal wetlands, offering a scientific foundation for informed management strategies aimed at enhancing the carbon sequestration potential of these vital blue carbon ecosystems.