Abstract: This paper aims to study on the Pinus armandii forest after nurturing in the Yunnan Forest Nature Center through a combination of field surveys, indoor measurements, and simulated combustion tests, to analyze the impact of pruning and thinning measures on the combustibility of the surface combustible fuels such as moisture, ash, crude fat, burning point, and calorific etc. The results showed that after nurturing, the height below the branches of the Pinus armandii forest increased to 6.3~8.5 m, the forest contains 1 900~2 700 trees per hectare, the moisture was below 15%, the ash contents were 2.94%~5.58%, the crude fat contents were 7.94%~8.09%, the ignition point was around 270 ℃, and the calorific value was 20 020~21 084 kJ/kg. In indoor simulated combustion, the ignition speed of combustible fuels did not exceed 2 s, the flame temperature was 462.0~475.8 ℃, and the flame radiation was between 6~7 kW/m². The moisture of the surface combustible fuels decreased after nurturing, which was beneficial for seedling growth. And the height below the branches in the forest increased while the height of the surface flame was 0.45~0.51 m. Accordingly, after nurturing, the surface combustible fuels in the Pinus armandii forest features low moisture and load, moderate ash and crude fat content, high burning point and calorific. At the same time, the nurture measures can prevent surface fires from developing into canopy fires and effectively reduce the risk of forest fires. The results are conducive to the adoption of more reasonable measures by the local area, thus achieving scientific fire management.

Key words: nurturing, combustibility, surface fuels, Pinus armandii, Kunming