Abstract: Under the background of global change, understanding the effects of nutrient addition on soil physicochemical properties and plant functional traits in coastal wetlands would provide a scientific foundation for the conservation and management of coastal wetland vegetation. Using field-manipulative experiments in the coastal wetlands of the Yellow River Delta, we investigated the soil physicochemical properties and changes in plant growth and physiological traits under the addition of different nutrients. Nutrients were applied annually from May to mid-August, with N, P, and K at a rate of 10 g·m^-2·a^-1 each. The results showed that N addition significantly increased soil nitrate (NO₃^--N), available nitrogen (AN), and available Cu by 98.6%, 98.7%, and 18.6% (P<0.05), respectively. Nitrogen addition significantly increased leaf area by 31.4%, canopy leaf area index by 29.2%, plant height by 13.6%, and increased leaf N, K, and Zn contents by 9.4%, 15%, and 30.7% (P<0.05), while it significantly reduced leaf Mg and Na contents by 21.6% and 48%, respectively (P<0.05). Phosphorus addition significantly increased soil TN by 33.3% and leaf TP by 17.7% (P<0.05), while it significantly decreased canopy leaf area index and Na content by 23.3% and 46.6%, respectively (P<0.05). Potassium addition significantly increased soil NO₃^--N, AK, and plant height by 72.9%, 52.3%, and 11.8%, respectively (P<0.05). Potassium addition also significantly decreased leaf Mg and Na contents by 24.2% and 60.3%, respectively (P<0.05). Additionally, redundancy analyses between plant functional traits and soil physicochemical properties revealed that soil N, P, K contents, pH, and conductivity significantly influenced plant growth and physiological indices. Therefore, environmental changes induced by exogenous nutrient inputs substantially impacted soil physicochemical properties and plant functional traits in the coastal wetland of the Yellow River Delta.

Key words: N addition, P addition, K addition, Yellow River Delta, common reed community, plant functional trait