The patterns of nearest neighbor trees in a temperate forest

The nearest neighbor trees (NNTs) are essential for reflecting forest structure and spatial heterogeneity in a forest stand. It is not clear whether different tree species have varied patterns of NNTs in a small area due to biological interactions, whether big trees affect the nearest neighbors for diversity and re-cruitments, or whether a universal linear relationship between the distance of NNTs and their average DBH exists. In this study, the information of NNTs at two plots (each 30 × 100 m) in a temperate mixed broadleaved forest in Southern USA was collected by field survey. Our results indicated that approximately 80% of NNTs were within a distance of 1.5-4.0 m. Tulip poplar, oaks, and hickory trees did not have the same species as NNTs or were very limited. Carolina buckthorn had itself as an NNT but with fewer other species. Sugar maple could serve as the NNT for oaks, hickory and others. The relationships between the distance of an NNT and its cumulative percentage were different among varied species or groups. Overall, for trees and their NNTs, there existed complicated relationships between their sizes ( e.g. , height and DBH). Big trees might affect NNTs in diversity and recruitment. The suggested linear relationship between tree size and distance was not observed. The results could be helpful to manage forest structure (tree species and NNT) and provide evi-dence to improve the scaling theory on NNTs.