Abstract: We investigated plant community for twice in a burnt area of Larix olgensis forest in Changbai Mountain Nature Reserve, to clarify the short-term impacts of forest fire on species composition, diameter class structure, and spatial distribution pattern of dominant species. The results showed that: (1) there were 14 tree species in the undisturbed plots, while 6 species was observed after 1 year of fire disturbance, and only 4 species were found after 4 years of fire disturbance. (2) The diameter class structure of the undisturbed plots showed an inverted “J” form, while the disturbed plots showed a normal distribution pattern. The fire resistance of dominant species (Larix olgensis and Betula platyphylla) of different diameter classes showed similar patterns, i.e., large diameter class>medium diameter class>small diameter class. (3) In the undisturbed plots, each diameter class of larch and birch showed a random distribution on the 0-25 m scale. However, the small diameter class (DBH<11 cm) of larch after 1 year of fire disturbance showed an aggregated distribution on small scale (r<12 m) and a random distribution on a large scale (12 m<r<25 m). The medium diameter class (11 cm≤DBH<21 cm) showed an aggregated distribution at 0-251 m scale, and the large diameter class (DBH≥21 cm) showed a random distribution pattern. The medium and large diameter classes of birch were randomly distributed at the 0-25 m scale. After 4 years of fire disturbance, the spatial distribution pattern of small diameter class and large diameter class of larch was similar to that after 1 year of disturbance, while the middle diameter class showed a clustered distribution on a small scale and a random distribution on a large scale. The medium diameter class of birch basically showed an aggregated distribution. Our results revealed the short-term dynamics of Larix olgensis forest after fire disturbance, providing guidance for regional forest restoration and management.

Key words: Larix olgensis forest, burned area, importance value, diameter size structure, point pattern analysis