25 Jul 2023
 | 25 Jul 2023

Formation of particulate organic carbon from dissolved substrate input enhances soil carbon sequestration

Qintana Si, Kangli Chen, Bin Wei, Yaowen Zhang, Xun Sun, and Junyi Liang

Abstract. Particulate organic carbon (POC) and mineral-associated organic carbon (MAOC), which are two primary components of the soil carbon (C) reservoir, have different physical and chemical properties and biochemical turnover rates. Microbial necromass entombment is a primary mechanism for MAOC formation from fast-decaying plant substrates, whereas POC is typically considered as the product of structural litter via physical fragmentation. However, emerging evidence shows that microbial by-products derived from labile C substrates can enter the POC pool. To date, it is still unclear to what extent labile substrates contribute to the POC formation and the subsequent long-term SOC stock. Our study here, through a 13C-labeling experiment in 10 soils from 5 grassland sites as well as a modeling analysis, showed that up to 12.29 % of isotope-labeled glucose-C (i.e., dissolved C) was detected in POC pool. In addition, the glucose-derived POC was dependent upon 13C-MBC and the fraction of clay and silt, suggesting that the POC formation from newly added labile C is dependent on interactions between soil physical and microbial processes. The modeling analysis showed that ignoring the C flow from MBC to POC significantly underestimated soil C sequestration by 7.79 % – 49.51 % across the 10 soils. The results emphasize that the soil texture-regulated microbial process, besides the plant structural residues, is a significant contributor to POC, acting as a vital component in SOC dynamics.

Qintana Si et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-1483', Anonymous Referee #1, 25 Aug 2023
  • RC2: 'Comment on egusphere-2023-1483', Anonymous Referee #2, 27 Sep 2023

Qintana Si et al.


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Short summary
Our soil incubation experiment demonstrates that dissolved labile carbon is a significant contributor to the formation of particulate organic carbon. The formation of particulate organic carbon from dissolved substrates is regulated by microbial biomass carbon and soil texture. The soil carbon model underestimates soil carbon sequestration when carbon flow from dissolved substrates to particulate organic carbon through microbial processes is not considered.