Fig. 1

Organ and total biomass of two ragweed at different growth stages (Mean ± SE). a–d Root, stem, leaf, total biomass for A. artemisiifolia. e–h Root, stem, leaf, total biomass for A. trifida. Different lowercase letters indicate significant differences in biomass at different growth stages but the same population density (P < 0.05), while different uppercase letters indicated significant differences in at different densities but the same growth stage (P < 0.05)