Objective  Forest floor is the main fuel of forest soil surface, and it is also the fundamental substance for wildfire to disturb the ecological process of boreal forest. Nutrient cycling and energy flow are the core contents for the ecological restoration of post-fire stands. In order to better understand the effects of fire disturbance on the forest floor carbon (C) and nitrogen (N) cycles of boreal forest ecosystem, this study explored the relationship between C, N or C/N ratio and spatial or temporal factors in post-fire forest floor.

  Method  In the forest floors (Oi horizon and Oe horizon) of different burned and unburned Larix gmelinii stands, the total organic C, N, ammonium N, nitrate N and soluble organic C contents were measured. We used one-way analysis of variance (ANOVA) to compare differences in the stoichiometric characteristics of forest floor C and N in post-fire forests, which were characteristics of different environments and time since fire. Pearson correlation was used to show the correlation between carbon content, nitrogen content, carbon nitrogen ratio and various factors; the influence of different factors on the stoichiometric ratio of carbon and nitrogen in forest floor was analyzed by factor analysis. ower than that in gentle slope (P > 0.05). In Oe horizon, the C and N contents of samples collected from gentle slope were slightly higher than that from flat slope, but the C/N ratio in flat slope was slightly higher than that in gentle slope. The sequential order of environmental factors affecting the C/N ratio in Oi horizon was longitude > latitude > ammonium N content > N content > C content > slope gradient > slope aspect > pH; whereas, in Oe horizon, the sequential order was longitude > C content > slope aspect > altitude > N content > pH > nitrate N content.

  Conclusion  Time since fire and environmental factors could influence C, N and C/N ratio in post-fire Larix gmelinii forest floor. Some environmental factors, such as slope gradient and slope aspect, could significantly affect the C, N and C/N ratio of post-fire Larix gmelinii forest floor. Time factor and environmental factors could affect the C and N cycles in post-fire boreal forest ecosystem by changing the decomposition rate of the forest floor.