Pattern and change of soil organic carbon storage in China: 1960s–1980s

Soils, an important component of the global carbon cycle, can be either net sources or net sinks of atmospheric carbon dioxide (CO₂). In this study, we use the first and second national soil surveys of China to investigate patterns and changes in soil organic carbon storage (SOC) during the period from the 1960s to the 1980s. Our results show that there is a large amount of variability in SOC density among different soil types and land uses in the 1980s. The SOC density in the wetlands of Southwest China was the highest (45 kg m⁻²), followed by meadow soils in the South (26 kg m⁻²), forest and woodlands in the Northwest (19 kg m⁻²), steppe and grassland in the Northwest (15 kg m⁻²), shrubs in the Northwest (12 kg m⁻²), paddy lands in the Northwest (13 kg m⁻²), and drylands in the Northwest (11 kg m⁻¹). The desert soils of the Western region ranked the lowest (1 kg m⁻²). The density of SOC was generally higher in the west than other regions. Eastern China had the lowest SOC density, which was associated with a long history of extensive land use in the region. The estimation of SOC storage for the entire nation was 93 Pg C in the 1960s and 92 Pg C in the 1980s. SOC storage decreased about 1 Pg C during the 1960s–1980s. This amount of decrease in SOC for the entire nation is small and statistically insignificant. To adequately characterize spatial variations in SOC, larger sampling sizes of soil profiles will be required in the future analyses.