Legacies of dead trees determine species interactions in forest communities

When plants die, neighbours escape competition. Living conspecifics could disproportionately benefit because they are freed from negative intraspecific processes; however, if the negative effects of past neighbours persist, other species may be advantaged and diversity maintained through ‘legacy effects’ of dead trees. Using large mapped forest plots, we examine whether antecedent communities shape forest dynamics and how long dead-tree legacies persist. We find that per-capita interaction strength of dead neighbours exceeds that of living trees, and that density-dependent effects from dead trees can persist for up to 10 years after death. Over 75% of species show negative responses to dead-tree neighbours, compared with 67% to living neighbours. Preliminary evidence suggests consistent legacy effects across tropical and temperate forests, with no clear mediating gradients. The drivers of tree legacy effects remain a mystery.