Cixi soil chronosequence: 0–2000y

The region has a subtropical climate characterized by monsoon rains, with a mean annual temperature of 16.3°C and an average annual precipitation of 1325 mm. The study area is a marine deposit plain composed of Yangtze River sediment, where paddy soil chronosequences representing approximately 50 to 2000 years of agricultural development were determined by historical dike construction records.

These records document a sequence of land reclamation, during which saline marshes were enclosed and gradually desalinized through leaching, enabling their conversion to rice cultivation. In these paddy fields, the typical cropping system consists of rice (Oryza spp.) grown during the wet season, followed by rice intercrops such as wheat, barley, and vegetables in the dry season. In late April 2018, paddy soil samples representing approximately 50, 100, 700, 1,000, and 2,000 years of cultivation were collected.