Spatial-temporal patterns of organic carbon sequestration capacity after long-term coastal wetland reclamation

Abstract

Reclamation significantly affects the dynamics of soil carbon, including carbon sequestration, emissions, and storage. In this study, the impact of the reclamation time (exceeding 1000 years) and land-use types on the carbon sequestration capacity of soil in the coastal wetland of Hangzhou Bay was investigated. We found that both pH and electrical conductivity (EC) negatively correlated with reclamation time, which was closely related to the degree of maturation of the soil and its distance from the coastline. The total organic carbon (TOC) content of the surface soil exhibited an upward trend as reclamation time increased. Total nitrogen (TN) and TOC exhibited a positive correlation, with the maximum values observed during the reclamation period from 1000 to 1500 CE. The land-use type had a significant effect on the TOC content of the surface soil. Surface soil TOC concentrations in different land-use types, in ascending order, were reed land, wastelands, vegetable fields, woodlands. This pattern suggests that the TOC of agricultural soil was higher than that of the soil from other land-use types. This increase in agricultural soil TOC was attributed to long-term fertilization. Soil organic carbon (SOC) content generally decreased with increasing soil profile depth. Therefore, in the early stages of reclamation, reasonable land management methods should be adopted to reduce SOC loss.