Interspecific association of main tree species in Ormosia microphylla community and its community stability

We investigated the interspecific relationships of Ormosia microphylla community in geomantic forest of Gutian Meeting site. The results showed that the main tree species in the arbor layer included Neolitsea aurata, Schima superba, Castanopsis carlesii, etc. while that in the shrub layer included Dendropanax proteus, Castanopsis fargesii, Diplospora dubia, etc. In the arbor layer, the niche breadth of O. microphylla was 21.04, and its niche overlap with the main tree species was low. The variance ratio and statistics of the main tree species in arbor layer were 0.77 and 59.57, respectively, indicating no significant association in arbor layer. In the χ² test, there were 101 pairs of non-significant species pairs, and the logarithm ratio of positive and negative association species was 1: 1.18, indicating that the interspecific association was weak. In the shrub layer, the niche breadth of O. microphylla was 21.60. There was a high niche overlap between the main tree species in the shrub layer. The variance ratio and statistics of the shrub layer main tree species were 1.80 and 138.68, respectively, indicating significantly positive overall association in shrub layer. In the χ² test, there were 107 pairs of significant species pairs, and the logarithm ratio of positive and negative association species was 1:0.09, indicating that the interspecific competition was strong. The Euclidean distances for the arbor and shrub layers were 6.40 and 4.91, respectively, suggesting the shrub layer was more stable than the arbor layer. In the shrub layer, there was a close relationship between O. microphylla and other main tree species. Due to intense resource competition, especially among the dominant species in the community, O. microphylla failed to achieve a dominant position as it grew into a mature tree. Therefore, there was an urgent need to implement artificial intervention measures and in-situ conservation strategies.