Abstract: Fire disturbance is a significant factor influencing aboveground biomass (AGB) in northern Chinese forests. The post-fire recovery of AGB depends on fire characteristics such as severity, frequency, and time since fire, and is also modulated by forest community structure. Elucidating the factors that drive AGB recovery in burned areas is essential for understanding community succession and carbon sequestration capacity in forest ecosystems. Focusing on the forests in the permafrost region of Daxing’an Mountains, a fire-prone area, we surveyed AGB and community structure in 2020 across 605 plots from large-scale burned areas with different fire histories, i.e., Mohe (burned in 1987), Huma (2003), and Songling (2006), along with 373 control plots, to analyze the effects of fire characteristics and forest community structure on AGB recovery. The results showed that: (1) AGB in the Mohe, Huma, and Songling burned areas (33, 17, and 14 years post-fire, respectively) was 81.1, 64.6, and 93.1 t·hm^-2, respectively. There were significant differences in AGB between burned and control plots in Mohe and Huma (P<0.05), but not in Songling (P>0.05). (2) Community diversity and stand age significantly influenced AGB in burned areas. Diversity and richness indices in burned areas were comparable to or significantly higher than those in control areas. Moreover, AGB in near-mature forests within burned areas more closely approached control levels than that in middleaged forests. (3) High fire severity significantly reduced AGB in burned areas. As fire severity increased (indicated by a decrease in the Normalized Burn Ratio), AGB exhibited a significant declining trend. (4) Fire severity and stand age explained 30% and 22% of the variation in AGB recovery, respectively, with contributions exceeding those of Shannon diversity index (10%) and species richness (5%). This study provides a scientific basis for understanding how fire disturbance and plant community structure jointly shape the patterns and drivers of AGB recovery in forest ecosystems.

Key words: aboveground biomass, forest fire disturbance, species diversity, stand age, fire severity