To study the niche, interspecific association and community stability of the main tree species in the community in order to understand the resource use habits of the species in the community and to understand the structure and stability of the community, which is of great importance for the sustainable management of forests, as well as for the restoration and reconstruction of degraded forests.

In this study, the natural forest community of Picea purpurea in the upstream reaches of Taohe river was taken as the research object. The niches, interspecific associations and community stability of the main tree species were analyzed by using Levins and Shannon niche breadth index, Pianka niche overlap index, variance ratio (VR), χ² test, association coefficient (AC), percentage of co-occurrence (PC), point correlation coefficient (PCC) and Godron stability.

The importance value and niche width of P. purpurea were the largest, and there was niche overlap with other main species, but the overlap index (O_ik) was less than 0.5. The overall performance of the main species in the community was not significantly positively correlated; the overall performance of the main tree species in the community was not significantly positively correlated, and the results of χ², AC, PC and PCC tests showed that the correlation between pairs of species in the community was not significant, and the correlation between species was relatively loose; the stability ratio of the tree layer in the community was (40, 60), which was far from the theoretical stability ratio (20, 80), indicating that the current purple spruce community was in a state of low stability.

The current P. purpurea community in the upstream of the Taohe river is unstable, and each species in the community shows an independent distribution pattern, and the correlation between the established species, P. purpurea and the other companion species is not high, and the competition is weak; Therefore, in the protection and restoration of P. purpurea community, species with similar ecological habits and biological characteristics should be selected to carry out artificial replanting measures to maintain interspecific balance and improve community stability.

To study the community structure and ecological status of the secondary succession stage in the degraded artificial spruce forest in the Bailongjiang forest area and predict the community's development trends.

Using sample plots to represent the comprehensive state of various resources and based on community survey data, we calculated species' importance values as niche measurement indices. We determined the niche width for dominant species using Levins' method, calculated Pianka's niche overlap, and analyzed overall species associations.

The results indicate that there were a total of 11 tree species in the secondary community's canopy layer. Artificial P. asperata trees had experienced significant mortality. The importance values and niche breadths of Betula albo-sinensis, Betula utilis, and Abies faxoniana were much larger than those of other species, establishing them as dominant species in the secondary community. A. faxoniana had the widest niche breadth in both the canopy and shrub layers, while Betula species were dominant in the canopy layer but not in the shrub layer. The secondary plant communities, there was generally a significant degree of niche overlap in the tree layer, which was greater than that in the shrub layer. Shrub communities exhibit niche differentiation. Overall, there was no significant positive correlation among species in both the canopy and shrub layers.

This study indicates that the secondary community is a Betula-Abies faxoniana forest community, currently in the mid-successional stage of positive dynamics and competitive equilibrium. The dominance and niche of various populations are still undergoing mutual adaptive changes, rendering the community relatively unstable. There is no clear correlation between species importance values and niche breadth, nor is there a definite pattern between niche overlap and niche breadth. Niche overlap further reflects the community's stability. The degree of dominance and niche breadth among coexisting species in the canopy and shrub layers reflect species growth potential. Therefore, the tree layer's stability in this secondary community is greater than that of the shrub layer. The A. faxoniana population is showing a further growth trend, while the birch population is restricted in its regeneration and is gradually being replaced by shade-tolerant tree species. Therefore, management in this secondary forest area should create favorable conditions for the growth of A. faxoniana.