Intraspecific and interspecific competition of Pinus tablaeformis natural secondary forests in western section of Qinling Mountains

【Objective】 This study aimed to ascertain the competition relationship of different Pinus tablaeformis populations and provide a scientific basis for protection and sustainable management of P.tablaeformis natural secondary forests in western section of Qinling Mountains.【Method】 The intraspecific and interspecific competition intensities were quantitatively analyzed by Hegyi single-tree competition index model.【Result】 The intraspecific competition intensity(competition index 145.50) was greater than the interspecific competition intensity(competition index 47.29) in P.tablaeformis population.The competition intensity gradually increased with the increase of diameter scale when DBH was between 5 cm and 25 cm while it decreased when DBH was greater than 25 cm.The competition intensities of P.tablaeformis populations ranked as the following order:P.tablaeformisQuercus aliena var.acuteserrataPopulus simoniiBetula platyphyllaLindera obtusilobaCarpinus turczaninowiiPrunus padusPinus armandiiCrataegus pinnatifidaPopulus davidianaQuercus liaotungensisBetula albo-sinensis var.septentrionalisQuercus baronii.The competition intensities between DBH of target trees and the intraspecific,interspecific,and total stands followed exponential function.There was a significant negative correlation between competition intensities and DBH of target trees.The competition intensities of the population reduced significantly with smaller amplitude when DBH reached 25 cm.【Conclusion】 The tending management should be actualized before DBH of P.tablaeformis reaches 25 cm in natural conditions for reducing the competition intensities of P.tablaefoemis populations and stabilizing the ecosystems as soon as possible.