Priming effects by cellulose inputs decrease with warming regardless of the decomposition stages of soil carbon pools

Soil comprises diverse carbon (C) pools undergoing various decomposition stages, each characterized by distinct stability and turnover rates. The response of these C pools to warming with the input of plant residues remains unclear.

We conducted a 90-day incubation study at 15 °C and 25 °C, introducing ¹³C-labeled cellulose into soils from old-field (OF), bare-fallow (BF), and bare-fallow plus 815-day pre-incubation (BF+) representing different stages of soil organic matter decomposition.

We estimated the priming effects (PE) of cellulose and found that PE were 30.6%, 59.3%, and 63.0% at 15 °C, and 20.8%, 35.3%, and 39.8% at 25 °C for OF, BF, and BF + soils, respectively. Net C balance was higher in BF and BF + soils than in OF soil by 0.6 − 2.8 mg C g⁻¹ SOC at 15 °C and 1.8 − 3.8 mg C g⁻¹ SOC at 25 °C. This indicated both PE and net C balance declined with warming regardless of soil C pool stability, but much greater in soil C pools at a slower decomposition stage.

Overall, this study underscores warming can uniformly decrease soil C sequestration potential although the distinct priming effects of the soil C pools at different decomposition stages.