Objective This paper analyzes the development stages and stand structure characteristics of hard broadleaved forest in Maor Mountain, Heilongjiang Province of northeastern China, identifies stand index changes at different stages, and provides scientific basis for the growth prediction and multifunctional sustainable management of natural secondary forests.

Method Taking the natural hard broadleaved forest of Maor Mountain Experimental Forest Farm in Heilongjiang Province as the research object, we used TWINSPAN bidirectional indicator species analysis method, interspecific linkage cluster analysis method, and discriminant analysis method to divide the development stages of hard broadleaved forests; selected different forest stand indicators from the aspects of age structure, diameter structure and tree species diversity, and analyzed the structural characteristics of stands at different developmental stages; and 11 parameters, including forest stability, target tree species diversity index and simpson diversity index, were combined through entropy weight method-AHP method, and a phased composite index was constructed.

Result The development process of natural hard broadleaved forest in Maor Mountain can be divided into group establishment stage, competition growth stage and near natural forest stage. At different stages, the age structure shows an increasing pattern, while the diameter structure generally shows an anti J-shaped pattern and the species composition is rich and relatively stable. Based on the three developmental stages, combined with the selected 11 parameters, the range of developmental stages divided by composite index F was given.

Conclusion The TWINSPAN classification method can effectively divide the developmental stages of natural hard broadleaved forests in Maor Mountain, and reveal the characteristics of their age structure, diameter structure, and species diversity at different stages. It provides a reference for the development targeted management measures in the study area.