Carbon gain in upper but loss in deeper cropland soils across China over the last four decades | Vien Khoa Hoc Ky Thuat Nong Nghiep Mien Nam

Carbon gain in upper but loss in deeper cropland soils across China over the last four decades

Wednesday, 2025/01/15 | 08:24:37

Zhenghu Zhou, Chuankuan Wang, Yu’e Li, Xuhui Wang, Xinhua He, Minggang Xu

PNAS; December 31, 2024; 122 (1) e2422371122. https://doi.org/10.1073/pnas.2422371122

Significance

Reports of soil organic carbon (SOC) dynamics in China’s croplands vary substantially due to diverse data sources and the lack of a standardized methodology. Additionally, SOC dynamics in deeper soil often receive insufficient attention. By conducting uniformly methodological resampling of whole-soil profiles at the same locations in 1980 and 2023, we present a national atla of SOC dynamic. Significantly, an overall net accumulation of 0.74 Pg SOC results from gains of 0.86 Pg SOC at the upper 0 to 60 cm soil layers but losses of 0.12 Pg SOC at the deeper 60 to 100 cm soil layers due to intensified decomposition driven by increased temperatures. Our findings provide insights into SOC responses to climate warming and agricultural carbon accumulation strategies.

Abstract

Increasing soil organic carbon (SOC) in agricultural systems is a primary nature-based option for mitigating climate change, improving soil fertility, and ensuring food security. However, the consequences of global warming and increases in carbon inputs on cropland SOC stocks over the last few decades remain largely unknown, particularly in deeper soil layers. Here, by using repeated measurements, we reassess variations in SOC stocks across a 0 to 100 cm soil profile at the same locations in China’s upland croplands in 1980 and 2023. We observe an overall net accumulation of 0.74 Pg SOC (7%) with a mean sequestration rate of 13.7 g SOC m⁻² y⁻¹. This accumulation results from 0.86 Pg SOC gains at upper soil depths (0 to 60 cm) induced by carbon inputs, alongside 0.12 Pg SOC losses at deeper soil layers (60 to 100 cm) prompted by warming-enhanced decomposition. While our findings indicate a successful, though lower than expected, increase in overall net SOC stocks, the loss of more recalcitrant deeper SOC warrants further consideration of its effects on enhancing cropland SOC accumulation to achieve carbon neutrality over the long term.

See https://www.pnas.org/doi/10.1073/pnas.2422371122

Figure 1:

Spatial distribution of 205 resampling sites across China’s upland croplands. Blue and black dots represent sample sites in 2023 and 1980, respectively. The depth of resampling is 100 cm (0 to 20, 20 to 40, 40 to 60, and 60 to 100 cm). Shaded areas are soil organic carbon (SOC) stocks in 1980 (SOC_1980).

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