Soil organic carbon content and storage of raised field wetlands in different functional zones of a typical shallow freshwater lake, China

Abstract

Soil samples were collected in raised-field wetlands of five typical functional zones (inlet zone, water reserve zone, outlet zone, aquaculture zone, industrial zone) in Baiyangdian Lake, China, from a depth of 0–30 cm. The soil organic carbon (SOC) content, density, and storage, and carbon pool index (CPI) were calculated for each typical zone, and spatial distribution of SOC storage in the region was estimated using the ordinary kriging, interpolated value method. Our results showed that the average values of SOC content and storage decreased with depth along the soil profiles. Lowest values of SOC content and storage were observed in the inlet zone, whereas the outlet zone showed the highest SOC content and the water reserve zone showed the highest SOC storage. Surface soils had higher heterogeneity with higher values of SOC content and storage than deeper soils. Storage of SOC was much lower in the south-east of the water reserve zone and the east of the inlet zone than in the north-west of the water reserve zone or in the east of the whole Baiyangdian Lake. Values of CPI followed the order water reserve zone > aquaculture zone > outlet zone > industrial zone > inlet zone. The SOC was positively correlated with water content and negatively correlated with soil bulk density (P < 0.01), but had no significant correlation with other soil properties.