Objective Species composition and diversity characteristics of Betula alnoides natural forests were investigated to provide evidences for biodiversity conservation of B. alnoides natural forests as well as close-to-nature management of B. alnoides plantation.

Method Plots with total areas of 10, 000 m² and 5, 000 m² were set up to investigate the species diversity in the forests at Pailuo Mountain, Ruili (PLS) and Huatao Ridge, Mangshi (HTL), Dehong Prefecture, Yunnan Province, respectively. The former stand was naturally regenerated after clear-cutting in 1958, while the other was naturally regenerated on abandoned land after slash-and burn cultivation in 1967. The Simpson index, Shannon-Wiener index and Pielou evenness index were used to analyze the species composition and diversity of tree, shrub and herb layers. The diameter class distributions were analyzed for the whole stand and the main tree species with importance value above 5.00%.

Result There was no absolute dominant species in PLS stand, and the most important species in PLS was Machilus pingii (14.76%) and B. alnoides (9.55%). The species with the largest important value in HTL stands was B. alnoides (26.47%), which was absolutely dominant in the stand. The species richness (except herb layer), Simpson dominance index, Shannon-Wiener diversity index and Pielou evenness index in each layer of PLS stand were higher than those of HTL stands, but the species dominance was lower in PLS stands. The species distribution was more evenly distributed in PLS stand. Simpson dominance index, Shannon-Wiener diversity index and Pielou evenness index were the highest in shrub layer, while the highest species richness was observed in tree layer. The diameter-class structures of both the stands were inverted J-shaped, and the main tree species with important value above 5.00% were concentrated in the middle and small sized classes except B. alnoides which was in large and middle-sized classes.

Conclusion The PLS stand is much closer to late succession stage than HTL stand, and they all belong to stable coenotypes. These findings could provide evidences and technical support for conservation of B. alnoides natural forest and close-to-nature transformation and management of B. alnoides pure plantation.