Effects of Wetland Restoration on Sulfur and Arylsulfatase in Mangrove Surface Soils at Jinjiang Estuary (Fujian, China)

As the fourth most essential nutrient element, sulfur plays an important role in plant growth and development, but limited information is available regarding sulfur and its bioavailability after the restoration of degraded wetlands. A field experiment was conducted on three different mixed-vegetation types and planting densities to investigate the effects of vegetation type and density on sulfur and arylsulfatase in mangrove surface soils at the Jinjiang estuary in China. The total sulfur (TS), H2O-S, absorbed-S, available sulfur (AS) and arylsulfatase contents in soils 2 and 3 years after restoration were measured, and the sulfur availability index (SAI) was calculated. The results indicated that vegetation type and planting density significantly affected the TS and bioavailability of soil sulfur, and higher TS, H2O-S, absorbed-S, AS and arylsulfatase contents appeared at LQT 1.0 × 1.0 m (1918 mg/kg, 137 mg/kg, 387 mg/kg, 960 mg/kg and 38 μg*g−1*h−1, respectively). Furthermore, the bioavailability of sulfur increased after restoration from the second to third year. Arylsulfatase was significantly correlated with AS (p < 0.05) and highly correlated with soil organic matter (SOM) (p < 0.01), but no significant correlations were observed among arylsulfatase, SOM and TS. No sulfur fertilizer was required for mangrove plants during restoration in this study area.