Spatial distribution patterns and associations of Pinus koraiensis and Tilia amurensis in broad-leaved Korean pine mixed forest in Changbai Mountains

Based on the investigation data from a 25 hm2 broadleaved Korean pine (Pinus koraiensis) mixed forest plot in Changbai Mountains of China, the dominant species Korean pine and Tilia amurensis were chosen as research objects. One point pattern analysis method, O-ring statistics, was used to analyze the spatial patterns of the species in three vertical layers, i. e., overstory, midstory and understory layers, and the spatial associations of intra- and inter-species between different vertical layers were studied. The results showed that P. koraiensis and T. amurensis were clumped at smaller scales. Higher layers tended to be randomly or regularly distributed, while lower layers tended to be aggregated at smaller scales. The aggregation degree decreased with canopy height. P. koraiensis stems in overstory layer were significantly positively associated to the stems in midstory layer at scales < 11 m, and T. amurensis in overstory layer showed negatively correlation with that in midstory and understory layers. Ther