Influences of anthropogenic cultivation on C, N and P stoichiometry of reed-dominated coastal wetlands in the Yellow River Delta

• The atomic C:N:P ratios in both soils and plants were not well-constrained.
• Atomic N:P ratios in both soils and plants were well-constrained in wetlands.
• The N limitations in the soils and P limitations in the plants were found in coastal wetlands.

Motivated by the previous studies that indicated well-constrained carbon:nitrogen:phosphorus (C:N:P) ratios in planktonic biomass, and their importance to improve our understanding on the biological processes and nutrient cycling in marine ecosystems, ecologists have endeavored to search for similar patterns and relationship in terrestrial ecosystems. Recent analyses indicated that “Redfield-like” ratios existed in plants; such data might provide insight into the nature of nutrient limitation in terrestrial ecosystems. We attempted to determine if analogous C:N:P stoichiometrical ratios exist in the soil and plant in the reed-dominated coastal wetlands of the Yellow River Delta (YRD). Under the influences of anthropogenic cultivation in the YRD, the reed-dominated wetlands could be classified into three categories, new-born wetland (NW), farmland converted into wetland (FW) and cotton wetland (CW). In these three wetland categories, our results showed that atomic C:N:P ratios (RCNP) in both the soil (42.6:1.6:1, 71.2:2.0:1 and 63.2:1.9:1, respectively) and the plant (1753:22.4:1, 1539:23.0:1 and 1196:23.8:1, respectively) were not well-constrained. Though C:N ratios (RCN) and C:P ratios (RCP) were of relatively large variation among different wetland soils and plants, average atomic N:P ratios (RCN) in both the soil (~ 1.9:1) and the plant (~ 23:1) were well-constrained in the reed-dominated wetlands at the YRD scale, suggesting that the N limitation and P limitation were found in the soils and the plants, respectively. The results potentially provide a useful reference for ongoing wetland conservation and restoration in the YRD.