In the classical theories, an important prerequisite for species coexistence is that intraspecific competition should be stronger than interspecific competition, and most of those theories are species-based, i.e. spatially implicit. However, trees are sessile and thus compete locally with individuals nearby, not with other species, within a certain range; an individual experiences “matchups” against each of the individuals nearby and the winner goes into the next stage. In addition, the range becomes wider as the tree size increases. Thus, competition between trees can be viewed as an accumulation of matchups with neighboring individuals changing across life stages.
In this study, we enumerated all matchups experienced by every individual for 8 major species in a mixed-species temperate forest, across 7 life stages from seeds to adults. We found consistently lower frequencies of conspecific matchups in most species, and relative importance of the conspecific matchups varied significantly between life stages and between species. Furthermore, we also found substantial asymmetry in individual matchups; the importance of “opponent” species of matchups often differed within species pair. The results based on the matchup disagree with the classical theory and these inconsistencies appear to relax the condition of species coexistence.