Changes in soil macrofaunal communities along soil age gradient under centuries of cultivation after coastal reclamation

Reclamation is a traditional method used to create new land from coastal wetlands for releasing pressures from human social development. Knowledge on the biological succession and mechanisms along soil development is important for enhancing biodiversity conservation after wetlands converted to lands. In this study, a 500-year soil chronosequence was identified at the coastal area of the Yellow Sea, China. The soil properties, soil macrofaunal communities and their relationships were studied in croplands (soil aged 35, 55, 100, 200, 300, and 500 years) on the reclaimed coastal area. Soil organic carbon (SOC), total nitrogen (TN), and total phosphorus increased significantly along the soil age gradient, whereas soil soluble salinity (SSS) and pH decreased, while bulk density, water content, and the carbon-nitrogen ratio fluctuated. SSS, pH, and TN were the main factors indicating the soil ages. Changes in macrofaunal communities closely associated with soil age by logarithmic regression. No significant differences were detected in macrofaunal communities' comparisons of 55-year vs. 100-year, and 300-year vs. 500-year croplands. The functional composition varied significantly with the variations of the soil properties. Soil macrofaunal succession was mainly driven by changes of soil nutrient status. The higher biodiversity and more complex communities can be expected along the soil age gradient. SOC was distinguished as the main factor among the soil properties associating with the succession of soil macrofaunal communities. The long-term changes in macrofaunal communities were comprehensive responses to the variations of soil properties under centuries of cultivation after coastal reclamation.

Automated summary

This study in the coastal area of the Yellow Sea, China, identified a 500-year soil chronosequence and examined the changes in soil properties and macrofaunal communities in croplands of different ages. The results showed significant increases in soil organic carbon, total nitrogen, and total phosphorus, while soluble salinity and pH decreased along the soil age gradient. Soil macrofaunal communities were closely associated with soil age, driven mainly by changes in soil nutrient status.