Spatial and seasonal distributions of soil sulfur in two marsh wetlands with different flooding frequencies of the Yellow River Delta, China

Soil samples from 0 to 100 cm depth were collected in eight sampling sites (Sites A1, B1, C1 and D1; Sites A2, B2, C2 and D2) respectively along two 250-m length of sampling zones (Zone N and Zone S) from the Yellow River channel to a tidal creek in the short-term flooding and seasonal flooding wetland of the Yellow River Delta of China in fall of 2007 and spring of 2008 to investigate spatial and seasonal distribution patterns of total sulfur (TS) and their influencing factors. Our results showed that TS contents in both seasons in surface soil in Zone N increased with increasing distances away from the Yellow River channel except for Site D1 in fall. However, TS contents in both seasons in surface soil in Zone S showed a tendency of increasing and then decreasing with increasing distances away from the Yellow River channel. Relative to spring, the mean TS contents in surface soils were slightly higher in fall in Zone N, whereas an opposite tendency was observed in Zone S. The mean TS stocks were obviously higher in fall with 934.36 g/m2 and 877.77 g/m2 compared to those in spring with 729.85 g/m2 and 696.78 g/m2 in Zone N and Zone S, respectively. TS contents and stock generally declined with depth along soil profiles with one accumulation peaks at a soil increment of 40-60 cm. Topsoil concentration factors also indicated that TS had shallower distribution in soil profiles. Soil total carbon (TC), total nitrogen (TN), soil organic matter (SOM), salinity and silt exerted positive loadings on TS, while soil pH and depth exhibited a negative correlation with TS content.