Abstract: Understanding individual competition in Pinus massoniana and Schima superba forests with different mixed proportions can provide references for the construction of P. massoniana mixed plantation with harmonious interspecific relationship. We examined the intraspecific, interspecific and total competition intensities of P. massoniana by using Hegyi single-tree competitive index in four types of mixed forests, including type Ⅰ (control, ten P. massoniana), type Ⅱ (eightP. massoniana and two S. superba), type Ⅲ (seven P. massoniana and threeS. superba) and type Ⅳ (six P. massoniana and four S. superba). The average intraspecific competition indices of P. massoniana were following the order of type Ⅰ > type Ⅱ > type Ⅲ > type Ⅳ. In alldiameter classes, there was a significant difference between type Ⅰ and types Ⅱ, Ⅲ, Ⅳ (P<0.05), while there was no difference between types Ⅱ, Ⅲ and Ⅳ (P>0.05). The average interspecific competition index of types Ⅱ and Ⅲ were significantly different from that of type Ⅳ (P<0.05), while there was no difference between types Ⅱ and Ⅲ (P>0.05).  The power function or exponential function was the best fitting models between the total, intraspecific, interspecific competition indices and diameter at breast height (DBH) of P. massoniana. There was a negative correlation between competition intensity and DBH. In the mixed plantation of P. massoniana and S. superba, the competition pressure of P. massonianamainly came from intraspecific level, which remained stable and kept at a low level under DBH>20 cm.

Key words: Pinus massoniana, mixing proportion, intraspecific competition, interspecific competition.