Analyses of intraspecific and interspecific competition of Pinus sylvestris var.mongolica natural forest in Honghuaerji Nature Reserve of Inner Mongolia

The intraspecific and interspecific competition intensities of Pinus sylvestris var.mongolica Litv.,Populus davidiana Dode.,Betula platyphylla Suk.and Malus baccata L.(with DBH2 cm) in P.sylvestris var.mongolica natural forest in Honghuaerji Nature Reserve of Inner Mongolia were analyzed by the Hegyi's single tree competition index.The results showed that the dominant competitive and objective trees were both of P.sylvestris var.mongolica and B. platyphylla in the plot.The intraspecific competition intensity of P.sylvestris var.mongolica(0.534) was much higher than the interspecific competition intensity.The intraspecific competition intensity of P.sylvestris var.mongolica declined gradually with the DBH class increased.There was a power function relationship CI=A·D-B between the intraspecific competition intensity and the DBH of P.sylvestris var.mongolica,and the change of competition intensity was not obvious when the DBH above 30 cm.The competitive trees of P.sylvestris var.mongolica had a heavy competition pressure on the other tree species.