Abstract:In order to study the effects of soil physical properties on the morphological traits of constructive tree species and species diversity of Pinus tabuliformis-Quercus aliena var. accuteserrata mixed forest community in Qinling Mountains,15 sampling plots were set up in the regions where the pine and oak distributed densely, then the methods of Pearson correlation analysis and canonical correspondence analysis (CCA) were used to reveal the relationships between soil physical properties (bulk density, porosity, water capacity) and the morphological traits of constructive trees, species distributions and α-diversity indices. The results showed that: 1) Non-capillary porosity was significantly negatively correlated with the abundances of P. tabuliformis and Q. aliena var. accuteserrata (P<0.05), significantly positively correlated with the height and coverage of Q. aliena var. accuteserrata (P<0.05, and P<0.01), while total porosity was significantly negatively correlated with the abundances of P. tabuliformis (P<0.05). 2) Bulk density was significantly positively correlated with Patrick richness index, Simpson diversity index and Shannon-Wiener diversity index (P<0.05), while capillary water capacity was negatively correlated with the Pielou evenness index (P<0.05). 3) The CCA ordination showed that the bulk density, maximum water capacity and capillary water capacity were the dominant factors determining the species distributions, many herbs tended to distribute in areas with higher bulk density and lower water capacity. 4) All of the species diversity indices in different community layers distributed in four independent intervals of CCA diagram with obvious boundaries along the bulk density gradient. Increase of bulk density promoted the diversity of herb layer, while increase of capillary water capacity promoted the diversity of tree layer. Species diversity indices of total community had maximum values under the medium environmental gradient. In conclusion, soil physical properties had produced significant impacts on morphological traits of constructive trees and species diversity of pine-oak mixed forest, thus, keeping a medium level of bulk density and water capacity, appropriately improving the shrub layer richness and tree layer evenness, are helpful to maintain higher species diversity of P. tabuliformis - Q. aliena var. accuteserrata mixed forest community in Qinling Mountains.