Abstract: We investigated the distribution of inorganic sulfur forms in the typical Cyperus malaccensis marsh in the Minjiang estuary by conducting a field nitrogen (N) addition experiment with four N addition levels (no N treatment, N₀, 0 g N·m^-2·a^-1; low N treatment, N_L, 12.5 g N·m^-2·a^-1; medium N treatment, N_M, 25.0 g N·m^-2·a^-1; and high N treatment, N_H, 75.0 g N·m^-2·a^-1) . Results showed that the contents of water-soluble-sulfur (H₂O-S) and HCl-soluble-sulfur (HCl-soluble-S) in marsh soil increased with N addition levels, and the values in the N_L, N_M and N_H treatments increased by 36.0%, 11.6%, 7.5% (H₂O-S) and 12.8%, 4.8%, 9.0% (HCl-soluble-S), respectively. The contents of adsorbed-sulfur (Adsorbed-S) and HCl-volatile-sulfur (HCl-volatile-S) decreased by 45.8%, 37.0%, 4.0% and 6.1%, 1.7% and 3.3%. N addition generally increased the contents and stocks of total inorganic sulfur (TIS). Compared with the N₀ treatment, the TIS content in the N_L, N_M and N_H treatments increased by 29.1%, 8.2% and 25.6%, while its stock increased by 23.1%, 13.7% and 25.6%, respectively. The elevation of TIS stock mainly rested with the contributions of H₂O-S and HCl-soluble-S. The variations of inorganic sulfur forms were mainly dependent on the alterations of N nutrient (especially NH₄⁺-N/NO₃^--N) and pH, and the relationships of S nutrient between plants and soils. Under N enrichment, the content and stock of TIS showed an increasing trend, indicating that the available S absorbed and utilized by plants was elevated and the increasing trend was particularly evident in the high N addition treatment (N_H).

Key words: inorganic sulfur form, nitrogen addition, marsh soil, Cyperus malaccensis, Minjiang estuary