Effects of experimental nitrogen additions on plant diversity in tropical forests of contrasting disturbance regimes in southern China

► Nitrogen addition had no significant effect on understory plant diversity in the disturbed forest. ► Nitrogen addition significantly decreased understory plant cover. ► Nitrogen addition had no effect on richness and density in the rehabilitated forest. ► The decrease is largely a function of a significant increase in canopy closure. ► Land-use practices may dominate the responses of plant diversity to N addition.