Fire disturbance may indirectly affect soil carbon mineralisation through shifts in fungal life strategies

Understanding the interaction between forest fires and soil organic carbon (SOC) dynamics is crucial for studying the carbon cycle of boreal forest ecosystems and its influence on global climate change. In particular, the impact of forest fires on the rhizosphere soil, which is a carbon-rich and ecologically sensitive microenvironment, was particularly significant. We used the rhizosphere soil of Larix gmelinii forests, a representative species of boreal forests in China, to investigate the mechanisms by which fungal life strategies affect post-fire soil carbon mineralisation in boreal forests in China. The SOC mineralisation was determined using indoor incubation for 50 days, and bacterial and fungal communities were detected using 16S rRNA and internal transcribed spacer (ITS) gene sequencing. We found that the rhizosphere soil dominated SOC mineralisation, and carbon release from the rhizosphere soil was significantly reduced by 53.8% after fire. In addition, the number of r -strategist microorganisms increased, and the number of K -strategist microorganisms decreased after the fire, resulting in a more pronounced domination of the rhizosphere soil by the r -strategy. Notably, the ratio of Copiotrophs to Oligotrophs in rhizosphere soil fungi was negatively associated with SOC mineralisation, and this ratio increased post-fire, potentially contributing to reduced SOC mineralisation through its relationship with β-1,4-glucosidase (BG) activity. The study revealed the complex regulatory mechanisms of forest fires on soil microbial community structure and SOC mineralisation from the perspective of soil microbial life strategies, which are essential for post-fire ecological restoration strategies.