Analysis of spatial patterns and spatial association between the invasive tree-of-heaven (Ailanthus altissima) and the native black locust (Robinia pseudoacacia)

Invasive exotic plants can persist and successfully spread within ecosystems and negatively affect the recruitment of native species. The exotic invasive Ailanthus altissima and the native Robinia pseudoacacia are frequently found in disturbed sites and exhibit similar growth and reproductive characteristics, yet each has distinct functional roles such as allelopathy and nitrogen fixation, respectively. Spatial point pattern analysis of trees in a silvicultural experiment was used to analyze the potential intraspecific and interspecific interference between these two species by looking at their individual spatial distribution and their spatial association. Analysis of spatial point patterns in the field with Ripley's K indicated that A. altissima and R. pseudoacacia were positively associated with each other along the highly disturbed skid trails in the majority of the field sites. Robinia pseudoacacia was clumped in the majority of the sites, whereas A. altissima was randomly distributed in most sites. Locally, increased disturbances could lead to more opportunities for A. altissima to invade, interact with R pseudoacacia and other native species and potentially have an effect on the native plant community.