Background: Regeneration is an extremely important and complex ecological process, which is disturbed by many factors. The current stand structure has an important influence on regeneration. The aim of this study is to provide theoretical reference for improving the regeneration capacity subtropical evergreen broad-leaved forest and formulating management measures of regeneration restoration.
Methods: A permanent plot of 100m × 100m was set up in the evergreen broad-leaved forest of Tianmu Mountain National Nature Reserve, Zhejiang Province, China. The plot was divided into 25 survey units of 20m × 20m by the adjacent grid survey method, and all the trees in the plot were investigated. The tree height, DBH, crown width, density, species richness index, aggregation index, competition index and mingling of each forest stratum were used as the stand structure index. The tree height, DBH, crown width, density and species richness index of regeneration trees were used as regeneration indicators. Redundancy analysis (RDA) was used to explore the relationship between forest strata structure and regeneration of evergreen broad-leaved forest.
Results: In the whole stand, DBH, tree species richness index and crown width were the main structure factors affecting regeneration. In the upper forest stratum, the tree height was the main structure factor affecting regeneration. In the middle forest stratum, the tree species richness index and crown width were the main factors affecting regeneration. In the lower forest stratum, crown width, competition index, tree height and tree species richness index were the main factors affecting regeneration. The effects of tree species richness index and crown width on regeneration in the whole stand were mainly reflected in the middle and lower forest strata in each forest stratum.
Conclusions: The influencing order of each forest stratum structure on regeneration was: lower forest stratum > middle forest stratum > upper forest stratum. Different regeneration indicators had different responses to the main stand structure indices, while the young tree height and DBH, and the tree species diversity and density of regeneration trees were most affected by the main stand structure indices. In order to promote the regeneration of evergreen broad-leaved forest in the future, different management measures should be taken for different forest strata, and the threshold value of each index should be controlled.