Abstract:

Objective: Community composition, structure, and interspecific correlations in dominant natural populations of Betula fujianensis, an endangered species in Luoboyan Nature Reserve of Fujian Province were investigated to reveal the interspecific relationships of the main species at different levels of B. fujianensis community, and mechanism of threatening the speceis, in order to provides a theoretical basis for the protection, habitat creation and population restoration of B. fujianensis community. Method: Based on the investigation of sample plots, the interspecific correlations in arbor, shrub and herb layers of the dominant population of B. fujianensis natural forest was studied using variance ratio, Pearson correlation test and Spearman rank correlation test, and ecological species groups were identified at different levels based on principal component analysis (PCA). Result: There were 207 species belonging to 133 genera and 89 families in the B. fujianensis community, including 64 species belonging to 40 genera and 25 families in the arbor tree layer, 112 species belonging to 63 genera and 39 families in shrub layer and 31, species belonging to 30 genera and 25 families in herb layer. The B. fujianensis is the first dominant species in the arbor tree layer, with an importance value of 23.55, followed by Phoebe bournei and Ilex formosana, with an importance value of 7.40 and 4.32, respectively. In the shrub layer, the first dominant species is Sarcandra glabra, with an importance value of 10.23, followed by Eurya loquaiana, E. weissiae, and Castanopsis fissa, with an importance value of 7.35, 5.31 and 5.09, respectively. The dominant species of herb layer are Woodwardia japonica, Plagiogyria adnata and Nephrolepis auriculata, with importance values of 17.24, 14.80, and 10.51, respectively, followed by Angiopteris fokiensis, Selaginella doederleinii, and Coniogramme japonica, with an importance values of 6.82, 6.67, and 5.13, respectively. The arbor tree layer and shrub layer showed significant positive association, while the herb layer showed non-significant positive association, indicating that the B. fujianensis community is generally stable.The results of Pearson correlation test and Spearman rank correlation test showed that the species pairs of significant positive correlations is greater than those of significant negative correlations among dominant populations in the community, and mainly of the species pairs are not significantly correlated or uncorrelated, indicating that most species have an independent distribution pattern. No significant correlation was found among B. fujianensis and Phoebe bournei and other tree species in the arbor tree layer, but the B. fujianensis is facing great competitive pressure in succession process due to its poor regeneration, and the P. bournei has become the first dominant tree species with good regeneration cycle. According to the correlations between species and PCA analysis, the ecological species groups of different layers were identified. The arbor tree layer and the shrub layer can be divided into four ecological groups, and the P. bournei in the arbor tree layer is a single group, which shows that it has a high independence, while the herb layer can be divided into three ecological groups. The species within the groups have convergent adaptability to the habitat, and the species among the groups have different ecological requirements. Conclusion: The community of B. fujianensis is generally stable, most of the populations are not significantly correlated or uncorrelated, most of the species have independent distribution. As the dominant tree species in the arbor tree layer, B. fujianensis is facing great competitive pressure in the process of succession due to its poor regeneration. The results are of great theoretical and practical significance for the protection and restoration of B. fujianensis community.

Key words: endangered species, Betula fujianensis, variance ratio, interspecific correlation, ecological species group