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Tree species exhibit complex patterns of distribution in bottomland hardwood forests

Dimov, Luben D., Chambers, Jim L., Lockhart, Brian Roy
Annals of forest science 2013 v.70 no.8 pp. 813-823
Quercus nigra, Quercus pagoda, hardwood forests, interspecific competition, intraspecific competition, trees, United States
•CONTEXT : Understanding tree interactions requires an insight into their spatial distribution. •AIMS : We looked for presence and extent of tree intraspecific spatial point pattern (random, aggregated, or overdispersed) and interspecific spatial point pattern (independent, aggregated, or segregated). •METHODS : We established twelve 0.64-ha plots in natural bottomland hardwood stands in the southeastern USA. •RESULTS : Spatial point pattern analyses (Ripley’s K, L, and L₁₂) indicated that, when species were combined, trees were frequently aggregated and less commonly overdispersed. Plots with larger trees were more likely to exhibit overdispersion, confirming a shift to this pattern as trees grow. The intraspecific pattern of cherrybark oak and water oak was either aggregated or random. Sweetgum was aggregated on all plots and always at smaller distances (less than 5 m) than the two oak species. Intraspecific overdispersion was very rare. Interspecific segregation among the two oak species was more commonly observed (six plots) than aggregation (one plot). Cherrybark oak and sweetgum were segregated at some scale on seven of the 12 plots and aggregated on only two plots. •CONCLUSION : The results from the analyses suggest that strong interspecific competition may result in segregation of trees from different species, while weaker intraspecific competition may lead to aggregations of conspecifics.