Study on interspecific associations of typical mid-subtropical natural broadleaved forest based on stratification

Stratification of arbor layer is popular in subtropical natural evergreen broadleaved forests. Two typical natural broadleaved forest communities in mid-subtropical zone were studied to reveal the interspecific associations of arbor layer and its sub-layers. There were 65 and 53 species in the arbor layer of the two communities, respectively.Arbor layer of the two communities could be divided into two sub-layers, light receiving layer (LRL) and non-light receiving layer (NLRL), and LRL dominated the communities. All species in LRL of two communities were totally negative association, which resulted in the totally negative associationin of arbor layer.Whether arbor layer or the two sub-layers, species in each layer could form numerous combinations in pair-wise approach, but most species tended to be independent with each other and few species were significantly positive or negative associated with other species, suggesting that random processes dominated the two communities. Attention should be paid to Sloanea sinensis and Neolitsea aurata in biodiversity protection practice since the former was always negatively associated with other species, while the later was mainly positively associated with other species among those species pairs with significant association.