Work

Biochar regulates soil organic carbon flow pathways via density fraction redistribution and priming effects

Year: 2026

Type: article

Abstract: The mechanisms underlying biochar's regulation of soil organic carbon (SOC) flow via heterogeneous density fraction distribution and fraction-specific priming effects remain unclear. To address this gap, a one-year incubation experiment was conducted using three agricultural soils amended with wood biochar. A BPCAs-based method was developed to quantify biochar's priming effects on native SOC (nSOC). Carbon flow pathways between soil fractions were inferred via δ 13 C differences among source-sink pools. Biochar amendment significantly increased SOC contents in free (fLF) and occluded light fraction (oLF). Increasing biochar application shifted SOC from dominant heavy fraction (HF, 80.4%–85.7%) to fLF (40.8%–64.6%), primarily due to low-density biochar input (51.5–83.1%). Prolonged incubation drove biochar-derived carbon migration from fLF to oLF and HF via organo-mineral interactions, modulated by soil carbon saturation capacity. Biochar induced sustained negative priming effect on nSOC, especially in fLF, likely driven by microbial substrate substitution, labile nSOC adsorption and soil microbial community shifts. This alteration, combined with biochar's redistribution, significantly redirected SOC flow pathways: from fLF → oLF → HF to oLF → fLF → HF. Extended incubation enhanced the negative priming in fLF, which suppressed nSOC degradation and reduced the probability of carbon flow from oLF to fLF. Conversely, biochar promoted carbon transfer from fLF to HF due to the intensified negative priming in fLF and its relative attenuation in HF. Overall, these findings demonstrate that biochar redirects inter-fraction carbon flow by coupling its mobility with priming induced nSOC degradation dynamics, providing a mechanistic framework for understanding biochar's role in SOC sequestration.

Source: Environmental Chemistry and Ecotoxicology

DOI: 10.1016/j.enceco.2026.04.017