Changes in soil organic carbon stocks from the 1980s–2010s in
northwest arid zone of China
Abstract
Soil is the largest carbon reservoir in terrestrial ecosystems, and thus
minor changes in it can dramatically affect atmospheric CO
2 concentrations. The fragile ecological environment in
the northwestern arid zone of China is susceptible to natural and
anthropogenic disturbances, which lead to variations in structure and
function of the ecosystem, as well as carbon source–sink dynamics. In
this study, digital soil maps of soil organic carbon stocks (SOCS) were
produced at a 90-m resolution for two periods (the 1980s and 2010s)
based on historical soil profile data and a random forest model. The
results showed that the prediction accuracy for SOCS in the topsoil
(0–30 cm) was superior to that of the subsoil (30–100 cm). Among them,
the mean annual evapotranspiration, normalized difference vegetation
index during the growing season, multi-year mean temperature, and clay
content were the main environmental factors affecting the spatial
distribution of SOCS. In the past 30 years, the SOCS of the northwestern
arid zone have decreased by 585.50 Tg, with a mean decline of 19.52 Tg C
yr -1. The changes in SOCS caused by land-use
conversion and reductions in SOCS were further shown to be attributable
to grassland desertification and agricultural reclamation. These
findings are valuable for exploring the carbon cycle in terrestrial
ecosystems in the context of global climate change and for achieving
China’s goal of carbon neutrality.