[Structure dynamics of communities after cutting along altitude in Mount Tianmu, China].

We examined the dynamics of community structure in forests formed after cutting all at altitude of 480, 580, 700 and 800 m of the Mount Tianmu National Nature Reserve in Zhejiang Province, from 2017 to 2020, using phytocommunity method. Results showed that the total number of plant individuals was 515 belonging to 50 species, 43 genera and 27 families in 2017. After three years, 30 new plant species emerged, belonging to 23 genera and 14 families, and the number of individuals increased by 116.9% in 2020. The new species were mainly , , , which primarily distributed at the altitude of 580 and 700 m. The tree species with the largest importance value in the communities at altitude of 580, 700 and 800 m remained stable, including , and , whereas that in community at altitude of 480 m changed from to . Meanwhile, the diameter distributions of community significantly differed across different altitudes. The diameter distribution of the community at altitude of 480 m displayed a single peak left skewness from the reverse 'J' type, whilst that at altitude of 700 m developed from a reverse 'J' type to an exponential type. The diameter distribution in the community at altitude of 800 m followed a normal pattern and the peak value shifted from 24 to 30 cm. Both the Simpson dominance index and Shannon diversity index of the four communities increased across the three years, and all decreased significantly with the increase of altitude. Meanwhile, diversity increased with rising altitude and increasing distance among altitudes. The recruitment of new species in 2020 provided sufficient seedlings and saplings for natural regeneration, but it had not yet succeeded to the subtropical climax community.