Decomposition of substrates with recalcitrance gradient, primed CO2, and its relations with soil microbial diversity in post-fire forest soils

<p><b>Purpose</b> Fire-induced changes in soil properties exert influence on soil processes, e.g., soil organic carbon (SOC) mineralization. The mineralization of organic substrates and soil priming effects in post-fire soils and the mechanisms involved remain elusive. This study aimed to investigate substrate mineralization with chemical recalcitrance gradient (sucrose, maize four, and maize straw) and induced priming effects on forest soils after the fire.</br><br/><b>Methods</b> Fire-burned forest soils (unburned as control) after 8 years were collected, and the physicochemical and biotic properties using high-throughput Illumina sequencing) were analyzed. Incubation of 42 days was conducted to investigate substrate decomposition and soil priming effects using the natural abundance ¹³C technique.</br><br/><b>Results</b> The bacterial community in soil after the fire event had high diversity and was dominated by the phyla of Actinobacteria, Proteobacteria, and Acidobacteria. The addition of substrate to the burned soil had larger mineralization and caused higher soil priming effects than the control soil. Positive priming of SOC by substrate was most likely attributed to "co-metabolism," indicated by the positive correlation between soil priming and sucrose mineralization.</br><br/><b>Conclusion</b> The intensity of substrate mineralization and soil priming effects in the burned soil depended on fire shifting microbial community and substrate quality itself.</br></p>