Abstract: In the pure forest of pinus yunnanensis in Zhaobi moun⁃tain, Xinping County, Yuxi City, Yunnan Province, a fixed sample plot was set up at the same location for 3 consecutive years. Through field survey and sampling,the ignition time, extinction time, radiant heat, flame height, spread speed and other fire behaviors of prescribed burning were observed, and the species composition, richness and frequency of shrubs and herbs in the sample plots of unplanned and planned burning were investigated and counted. The results showed that: with the increase of planned burning times,the height of shrubs, herbs and ferns decreased, which reduced the vertical continuity in the forest,and it was difficult to cause canopy fire even if fire occurred. After 3 years of continuous observation and investigation,the average surface fuel load was 0.85 ± 0.25 kg/m2 ,and the burning effect of planned burning was closely related to fuel load. In a short period of time, the species richness of shrubs and herbs in the sample plot was significantly reduced. After planned burning, the important value of Eupatorium adenophorum Spreng decreased, while the important value of bracken increased significantly.

Key words: burning rate, surface fuel, prescribed burning, pure forest of pinus yunnanensis