马尾松－川灰木人工混交林种内、种间竞争强度

To 30 m × 30 m plots in Pinus massoniana-Symplocos szechumensis mixed plantation in Jinchengshan National Forest Park of Nanchong, Sichuan Province were installed, and 30 representative individuals of P. massoniana in each plot were chosen as objective trees to measure their diameter at breast height, plant height, branch height, and crown diameter. Such measurements were also taken for all the competitive trees within and out of 6 m from the objective trees. Within an area with radius of 6 m, two circles were divided. The inner one was composed of the competitive trees that were nearest to the objective tree, while the outer one was composed of the rest competitive trees. Hegyi's simple competition index was used. The intra-and inter-specific competition intensities either in inner or in outer circle decreased with the increasing diameter class of the trees. The competition intensities were in the order of intraspecific competition of P. massoniana in inner circles ＞ interspecific competition between P. massoniana and S. szechumensis in inner circles ＞ intraspecific competition of P. massoniana in outer circles ＞ interspecific competition in outer circles.