Abstract: An across-scale spatial pattern analysis which is closely related to Ripley’s K statistic but without cumulate effect was conducted to characterize the spatial characteristics and associations of an old growth birch-fir forest located in Mt.Taibai,China.The study was designed to analyse the spatial distributions of trees in the forests for assessing the different tree species spatial distribution patterns of different trees’ classes to increase the understanding of the effects of spatial structure,spatial associations,species co-existence and forest form on pattern-process relationships in the forest.The modified spatial point ana-lysis methods,Univariate and Bivariate NDF(Neighborhood Density Function) were employed to capture spatial distribution pattern and characteristics of the forest.The results of this study showed that all species exhibited random distributions at most spatial scales.When joint forest canopy structure and spatial pattern were conducted,this related changes in vertical layers to changes in spatial pattern.The lower layers tended to be aggregated at most scales for all tree species.But the aggregation degree decreased with canopy height,and the scales decreasing with a layer height increasing.Betula albo-sinensis var.septentrio-nalis stems were significantly negatively associated to the Abies fargesii stems in forest at most scales,and there was no significant correlation between Abies fargesii and Salix yuhuangshanensis stems.The sequel of negatively associated was also observed between Betula albo-sinensis var.septentrionalis and Salix yuhuangshanensis stems.Betula stems were positively associated with conspecific dead trees but were limited in small scales(<5 m) suggesting that seed dispersal and vegetative regeneration influenced the spatial patterning of Betula by itself.Abies influenced recruitment and showed a negatively associated pattern and indicated intense competition with Betula in small scales(<5 m).The results elicited from NDF,the modified spatial point analysis suggested that different regeneration strategies among the species play an important role in regulating their spatial distribution patterns,while competition between individuals of Betula and Abies at the all stage also contributes to spatial patterning of these communities.The recruitment limitations of Betula and Abies may affect the persistence of these species and the long-term dyna-mics of the forest.The mechanism of co-existence of different species in Mt.Taibai should be investigate and discuss in a further research.