Abstract: Humulus scandens is a dioecious climbing herb. In April, a uniformly distributed wild H. scandens population was selected and managed only for controlling weeds. From the beginning of May, some parameters of H. scandens seedling, including density and height of population, individual’s module traits and biomass allocation, were determined for six consecutive times at an interval of 10 d. The purpose of this study was to analyze the relationships among population density, individual’s  module traits and biomass allocation during population selfthinning, and to explore the selfthinning law of H. scandens population. The results showed that H. scandens seedling was characterized by a significant selfthinning phenomenon. Population density decreased by 71% within 60 days. During seedling from upright growth to lateral growth, density and height of population were significantly reduced. Due to selfthinning, stem traits of remained plants were significantly changed in the following order: internode length > main stem length > stem diameter for stem traits; leaf traits varied in the following order: leaf area > petiole length > leaf thickness > leaf width > leaf length > total leaf number > reserved leaf number; and root traits: total root length > root volume > root number > root length > maximum root length. Component biomass and single plant biomass of remained plants were significantly elevated, yet biomass per unit area declined gradually. Allocation ratio of aboveground biomass of remained plants was relatively stable (P>0.05), while the ratios of root to stem and leaf to stem changed significantly (P<0.01). There was highly significant allometric relationship among leaf, stem, petiole biomass, root biomass and aboveground biomass (P<0.01). Leaf and stem presented a constant growth pattern with the increase of aboveground biomass. Meanwhile, leaf, petiole and root presented an allometric growth pattern with the increasing aboveground biomass. There was a highly significant correlation between aboveground biomass and leaf, stem, petiole and root biomass (P<0.01). The allometric relationship between stem biomass and density abided by the rule of final output constant. Leaf, petiole and root biomass did not follow -3/2 selfthinning rule, nor -4/3 selfthinning rule and -1 selfthinning rule. Both aboveground biomass and total single plant biomass were significantly correlated with the density (P<0.01). For remained plants, the allometric relationships among aboveground biomass, total biomass and density followed the rule of final output constant.

Key words: spatial variability, Huang-Huai-Hai Plain, sequestration rate., soil organic carbon