Abstract: Aims Natural secondary poplar-birch forest is one of main secondary forests in Changbai Mountain, which is formed by the
restoration after clear-cutting or fire. And it is an important stage in the secondary succession of broad-leaved Korean pine
(Pinus koraiensis) mixed forest. A 5 hm² natural secondary poplar-birch forest plot was established in Changbai Mountain
Natural Reserve in 2005 in order to gain insights into the processes driving regeneration and succession of the forest and
its climax community—broad-leaved Korean pine mixed forest. This paper aims were to give some basic information on the
forest, including species composition and community structure.
Methods In the plot, all free-standing trees at least 1 cm in diameter at breast height (DBH,1.3 m above ground) were
mapped, tagged, and identified to species, and their geographic coordinates were recorded following a standard field
protocol. A total survey station was used to determine the elevations of edge points.
Important findings There are 16 565 genotype individuals (20 101 individuals with branch), belonging to 44 species, 28
genera, and 16 families. Floristic characteristics of the community are very prominent. At the generic levels, North
temperate areal-type is the main part of genus areal-types. The statistics of species abundance, basal area, mean DBH, and
important value showed that pioneer species Betula platyphylla and Populus davidiana are obviously dominant species. However,
the regeneration of the two species is very poor by the analysis of size-class distributions, which indicated that they will
quit the stage along with the succession of the community. Some tree species, such as Korean pine and Tiliaam urensis, which
are main species in broad-leaved Korean pine mixed forest, account for a large proportion in the understory layer. Therefore,
they will replace the pioneer species and dominate the overstory layer. Spatial distribution patterns of species were
analyzed. For pioneer species and those species that are main species in broad-leaved Korean pine mixed forest, there is no
obviously clumped pattern captured. For the midstory and understory species, there are obviously clumped patterns of many
species by the observation. There is no obvious correlation between the clumped patterns and the topography.

Key words: community structure, biodiversity, natural secondary forest, forest dynamics plot (FDP), Changbai Mountain