Background Jinyun Mountain is located at the end of the Three Gorges Reservoir Area, with a forest coverage rate of 96.6%, and a large area of mixed coniferous and broad-leaved forests, which is an important carbon reservoir component of the Three Gorges Reservoir Area. Affected by extreme high temperature weather, a forest fire occurred in the southern foothills of Jinyun Mountain on August 21, 2022, and the author estimated the carbon release amount of litter layer and arbor irrigation layer under this forest fire disturbance, aiming to provide a scientific reference for the calculation of carbon loss after fire disturbance and the restoration of vegetation carbon sink function.

Methods Taking the coniferous and broad-leaved mixed forest of typical forest species in Jinyun Mountain in Chongqing as the research object, by dividing different levels of fire disturbance in Jinyun Mountain, setting up 12 fixed standard sample plots, biomass method was used to collect samples of trees, shrubs and litter layers after fire disturbance and undisturbed areas, comparing the differences between the two, and flux tower data was combined to estimate the carbon loss and carbon release under forest fire disturbance.

Results 1) The combustible load of litter layer and arbor layer in coniferous and brogd-leaved mixed forest mainly increased with the increase of blackening height and tree mortality. The combustible load of the shrub layer mainly decreased with the increase of blackening height and tree mortality. Combustible consumption under the same forest fire disturbance degree: litter layer (41.33 t/hm²) > shrub layer (1.28 t/hm²) > arbor layer (0.27 t/hm²), the combustibles were mainly litters and upper humus. The consumption of combustibles in various parts of the forest increases with the increase of forest fire disturbance. 2) There was a significant positive correlation between litter layer and arbor layer and blackening height and tree mortality (P < 0.01), and the correlation with other stand investigation factors was not significant, indicating that the combustible material load of litter layer and arbor layer increased with the increase of blackening height and tree mortality in coniferous and broad-leaved mixed forests. There was a significantly negative correlation between shrub layer and blackening height and tree mortality (P < 0.05), but not with stand investigation factors, indicating that the combustible material load of shrub layer decreased with the increase of blackening height and tree mortality after forest fire disturbance. 3) The carbon emission in the coniferous and broad-leaved mixed forest plot in Jinyun Mountain was mainly provided by severe fire disturbance, and the total fuel consumption and carbon release of the coniferous and broad-leaved mixed forest in Jinyun Mountain were 5 468.66 kg, the carbon release amount was 2 460.90 kg, and the total carbon absorption loss caused by forest fire disturbance was 5.68 t/(km²·d).

Conclusions To sum up, this study shows that the coniferous broad-leaved mixed forest of Jinyun Mountain is most disturbed by mild fire, and the surface fire is the mainstay, and the combustion materials are mainly litter and upper humus, and the total amount of combustible materials consumed is more and the total carbon release is large. The results may provide data reference for the study of carbon balance and carbon cycle in the study area, and provide a scientific basis for the later restoration of vegetation carbon sink function.