Niche Characteristics and Interspecific Relationships of Degenerated Pinus armandii Community in Shennongjia National Park

Studying the community structure and interspecific relationship at different levels of degenerated Pinus armandii community in Shennongjia National Park ecosystem can provide theoretical basis for vegetation restoration. The P. armandi community was taken as the research subject in this study, which has experienced the pest infestation of Dendroctonus armandi for 2 years. The species composition characteristics of tree layer and shrub layer were analyzed by using the indexes such as importance value, niche width and niche overlapping. The variance ratio method, Pearson correlation test and Spearman rank correlation test were used to study the overall interspecific association and relationship of the community. The findings revealed that there were 16 species of plants belonging to 14 genera and 10 families in the arbor layer and 35 species belonging to 30 genera and 23 families in the shrub layer. P. armandii and Rubus hirsutus were the first dominant species in the arbor layer and shrub layer. P. armandi and Toxicodendron vernicifluum had wider niche width in the arbor layer. Rubus hirsutus had the widest niche width in the shrub layer, and followed by Celastrus orbiculatus and Litsea pungens, which indicated that these species have strong habitat adaptability. The niche overlap indices of arbor layer and shrub layer were 0–0.96 and 0–0.85, respectively, in which the proportion of species pairs without niche overlap in arbor layer and shrub layer accounted for 32.50% and 67.90% of the total species pairs. These results showed that ecological resources had not been insufficient utilized in each layers, and this condition was more obvious in the shrub layer. The overall associations of tree layer and shrub layer were not significant positive. The results of correlation test showed that the number of species pairs with negative association was more than that with positive association, and the number of species pairs with significant or extremely significant negative association was also higher than that with significant or extremely significant positive association, indicated that the competition of the relationship among species was fierce. In arbor layer, P. armandi was significant positive connected wtih Quercus aliena var. acutiserrat, while was negative connected wtih most other species. To conclude, the P. armandii community was generally in an unstable state, and the interspecific relationship was mostly in a negative connection state. In the later process of vegetation restoration, natural restoration can be the main method. Appropriate tree species with wide niche and positive association with dominant tree species shall be selected for artificial replantation to promote vegetation restoration. At the same time, attention shall be paid to the protection of species habitats that may become endemic species to maintain biodiversity.