Questions: What are the primary types of intraspecific distribution patterns and interspecific associations of tree species in the temperate–subtropical transition region? Can potential ecological mechanisms such as habitat heterogeneity, dispersal limitation, density dependence, spatial segregation, and competition between species regulate these patterns?

Location: The Qinling Mountains, north‐central China.

Methods: Ripley's K‐function, D‐function and pair correlation function were applied to assess the spatial distribution of 15 dominant tree species in a fully mapped 25‐ha plot. Complete spatial randomness (CSR), heterogeneous Poisson (HP) and randomlabelling (RL) null models were used to reveal the potential process of community construction.

Results: (a) Thirteen of 15 adult tree species displayed an aggregation distribution at various scales. (b) Eleven adult species (73.3%) showed significant aggregation, especially at small distances, after removing the effect of habitat. (c) The percentage of species showing additional aggregation relative to adults decreased from saplings to juveniles. The maximum strength of density dependence was negative with species abundance. (d) Only 29 (13.8%) of the species pairs showed significant small‐scale interactions. Most of the significant small‐scale associations did not occur in abundant species pairs. (e) Negative interactions of interspecific associations were more prevalent than positive ones, yet there was no consistency of the characteristics among species pairs. Conclusions: Habitat heterogeneity and dispersal limitation likely contribute to the spatial pattern of tree species at different life stages. Density dependence remains the important factor in maintaining species diversity in this forest stand. Moreover, spatial segregation generates the interspecific spatial patterns of segregation and partial overlap. Unexpectedly, the species herd protection hypothesis and the lowfrequency hypothesis cannot well explain the mechanism of interspecific interaction at small distances. Resource competition might be responsible for negative associations being more frequent among species pairs.