Nutrient stoichiometry and trade-offs focusing on the mass balance of multiple nutrient elements play important roles in the response mechanism of plants to environmental stresses in wetlands. Nonetheless, little is known about the response dynamics and trade-offs of nutrient elements of wetland plants, especially potassium (K), under hydrological fluctuation conditions. Greenhouse experiments have been undertaken to assess the effects of initial water level (DW), water-level amplitude (AW), lasted time and their interactions on the response pro-cesses of nutrient stoichiometry of Carex schmidtii. Plant nutrient trade-offs and limitation were investigated under multiple hydrological fluctuation conditions. Results showed that plant nitrogen (N), K and their ratio were significantly influenced by DW. Lasted time significantly affected nutrient stoichiometry except for N:P ratio. Plant N:K ratio were sensitive to the three factors and their interactions. Moreover, plant N:P and N:K ratios indicated a significant P limitation and K limitation for the growth of C. schmidtii, respectively. The scaling exponents showed that DW, AW and their interaction have significant effects on the relationships of P - N, K - N and K - P. Principal component analysis indicated that lasted time had significant effects on the nutrient balances. Hydrological fluctuation resulted in changes in plant nutrients and their ratios, but nutrient trade-offs relieved the negative effects. These findings help in understanding the nutrient stoichiometry and response mechanism of C. schmidtii to hydrological fluctuation and provide invaluable information for nutrient and hydrological management for tussock wetlands.

Nutrient stoichiometry and trade-offs focusing on the mass balance of multiple nutrient elements play important roles in the response mechanism of plants to environmental stresses in wetlands. Nonetheless, little is known about the response dynamics and trade-offs of nutrient elements of wetland plants, especially potassium (K), under hydrological fluctuation conditions. Greenhouse experiments have been undertaken to assess the effects of initial water level (DW), water-level amplitude (AW), lasted time and their interactions on the response pro-cesses of nutrient stoichiometry of Carex schmidtii. Plant nutrient trade-offs and limitation were investigated under multiple hydrological fluctuation conditions. Results showed that plant nitrogen (N), K and their ratio were significantly influenced by DW. Lasted time significantly affected nutrient stoichiometry except for N:P ratio. Plant N:K ratio were sensitive to the three factors and their interactions. Moreover, plant N:P and N:K ratios indicated a significant P limitation and K limitation for the growth of C. schmidtii, respectively. The scaling exponents showed that DW, AW and their interaction have significant effects on the relationships of P - N, K - N and K - P. Principal component analysis indicated that lasted time had significant effects on the nutrient balances. Hydrological fluctuation resulted in changes in plant nutrients and their ratios, but nutrient trade-offs relieved the negative effects. These findings help in understanding the nutrient stoichiometry and response mechanism of C. schmidtii to hydrological fluctuation and provide invaluable information for nutrient and hydrological management for tussock wetlands.