Spatial patterns of natural regeneration for Korean pine (Pinus koraiensis) in response to tree species composition, Northeast China

Prior research has demonstrated that the natural regeneration of Korean pine ( Pinus koraiensis ) in old-growth forests is quantitatively constrained by the composition of parent trees. To further explore the spatial relationships between regenerated and maternal Korean pine, we examined the spatial patterns of its regeneration across four ontogenetic stages (younger seedlings, older seedlings, smaller saplings, and taller saplings) in five old-growth mixed forest stands representing a gradient of Korean pine basal area proportion (33%-77%). Using spatial point pattern analysis with crown-projected coordinates, we quantified intra- and interspecific spatial associations. Results revealed that Korean pine natural regeneration is forest-type-specific, with the ribbed birch ( Betula costata )-Korean pine forest being the most conducive to regeneration. Distribution patterns indicated a density-dependent ontogenetic shift: regenerated individuals exhibited strong aggregation at the early stage, which shifted to a random-dominated distribution in later stages, a trend amplified in stands with higher proportions of Korean pine. Associations between younger seedlings and parent trees transitioned from fine-scale facilitation to broad-scale repulsion ( p < 0.05), but only where the Korean pine proportion was approximately 50%. Notably, most heterospecific associations were neutral, with facilitation being highly species- and context-specific. We conclude that high conspecific occupancy intensifies intraspecific competition, whereas neutral associations with broadleaved species suggest that niche partitioning governs coexistence. Conservation strategies should therefore focus on regulating parent tree density and maintaining stand diversity to ensure sustainable regeneration. Methodologically, we recommend that future point pattern analyses of large canopy trees, particularly those with severe crown asymmetry, using crown coordinates.