Chen, Shaoqing; Feng, Puyu; Chen, Fangzheng; Ren, Jian; Liang, Hao; Gao, Yinan; Hu, Kelin
Abstract
Soil carbon sequestration should mitigate climate change, yet the dynamics of deep soil carbon are poorly known. Here, we conducted a 12-year field experiment in a Fluvic Cambisol under a wheat-maize rotation system, comparing straw return with straw removal, and quantified carbon stocks across a 0-200 cm soil profile. We traced carbon sources using both natural C-13 abundance, and C-13-labeled glucose in a 60-day laboratory incubation experiment. Results show that straw return increased soil inorganic carbon stocks by 57.6 t ha(-1) in the 100-200 cm layers. Pedogenic carbon increased by 96.6% in the 0-20 cm topsoil and by 97.7% in the 120-140 cm deep soil, whereas lithogenic carbon remained stable, indicating that soil inorganic carbon gains originated primarily from pedogenic carbonate formation. 72.23% of the added C-13-glucose was mineralized to CO2, while 17.27% was transformed into soil inorganic carbon, suggesting that exogenous carbon reaching the 120-140 cm soil layer can enhance pedogenic carbonate formation. Straw return increased microbial biomass carbon by 192% in topsoil and 144% in deep soil, and increased carbonic anhydrase activity by 43% and 73%, respectively. These findings reveal a previously overlooked, microbially-mediated mechanism for deep soil inorganic carbon accumulation, highlighting deep soil inorganic carbon as a stable carbon sink in alkaline croplands.
Identifying spatiotemporal patterns and driving factors of nitrogen leaching in Henan Province by integrating a process-based model with machine learning.pdf