Abstract: The aim of this study was to explore environmental factors affecting beta diversity and its components of secondary forest and to provide a theoretical basis for the protection and restoration of biodiversity in Lao Mountain. Based on the geographic coordinates and environmental factors of 69 sampling sites, using a Generalized Dissimilarity Modelling (GDM), we analyzed the relationship between beta diversity of different plant life types and the environmental factors. The relationship between different components of beta diversity and environmental factors was determined by Mantel test. The results of GDM showed that 10, 11 and 12 environmental variables affected beta diversity of trees, shrubs and herbs, with the explanation rate being 18.16%, 28.38%, and 43.61%, respectively. The effects of geo-distance, altitude and soil ammonium on the diversity of tree and shrub species were large, while the influence of geo-distance, pH and available potassium content on the diversity of herbage species was great. According to the results of beta diversity decomposition, the beta diversity of trees, shrubs and herbs of Lao Mountain’s forest community was dominated by turnover components. Geographical distance had a significant effect on the turnover of shrubs and herbs but did not affect that of trees. Altitude and soil nitrogen content significantly affected the turnover of trees and shrubs but did not affect herbs. Soil pH, organic matter content and available potassium had significant effects on the turnover of herbaceous species. Habitat filtration and dispersal restriction co-affected the beta diversity pattern, with higher impacts of habitat filtration. During the process of ecological restoration, attention should be paid to the effects of altitude, soil ammonium nitrogen content on woody species distribution and also to the effects of soil pH, organic matter content and available potassium content on herbaceous species distribution. Because the turnover components of beta diversity of trees, shrubs and herbs were much larger than that of nested components, species diversity conservation in the secondary forests of Lao Mountain should be carried out in an allround way.

Key words: beta diversity, Generalized Dissimilarity Modelling, turnover component, nested component, environmental factor.