Abstract: Species,mean coverage,mean density and α-diversity index of the understory herbaceous plants were investigated in five-year-old Liriodendron chinense forest stands different in canopy density in Chongming Island of Shanghai.Results show that with canopy density increasing from 0,(0,0.2],(0.2,0.4],(0.4,0.6],(0.6,0.8] and(0.8,1.0],the number of understory herbaceous plant species displayed a rising-and-then-falling trend,like 16,16,19,15,9 and 7.Significant negative correlations were observed between the canopy density and the mean coverage of herbaceous plants(r=-0.964 3,P<0.01)and the mean density of herbaceous plants(r=-0.981 5,P<0.01)as well.The Simpson index,Shannon-Weiner index,and Pielou index peaked when the canopy density was(0.2,0.4],being 0.754 8,1.327 3,and 0.880 6,respectively.

Key words: canopy density, young stand, understory herbaceous plant, species diversity, Liriodendron chinense