Abstract: Sparse understory vegetation with single species composition is a main cause of serious soil and water losses in Pinus massoniana forests in red soil region, and it is closely related with allelopathic effects of trees. In order to clarify the influence of allelopathy of tree’s rhizosphere soil on understory vegetation distribution, the effects of rhizosphere soil extracts of Pinus massoniana and Liquidambar formosana on four common herbs, i.e. Cynodon dactylon, Trifolium repens, Paspalum notatum and Poa annua, were studied. The results showed that: (1) Extracts from Pinus massoniana rhizosphere soil had obvious allelopathic inhibition effects on the four receptor plants under 1, 0.5 and 0.25 mg·mL^-1 concentrations. L. formosana rhizosphere soil extracts showed inhibition effects under 0.5 and 0.25 mg·mL^-1 concentrations, but had a certain stimulation effect under 1 mg·mL^-1 concentration. (2) For different concentrations of P. massoniana rhizosphere soil extracts, no obvious allelopathic effects was found on Cynodon dactylon, but the inhibition effects were enhanced with the increase of extract concentrations for the other three herb plants. For the three concentrations of L. formosana rhizosphere soil extracts, C. dactylon presented the effects of promoting at low concentration and repressing at high concentration, while T. repen and P. annua showed the effects of repressing at low concentration and promoting at high concentration, and P. notatum exhibited an inhibition effect with the increase of extract concentration. In terms of allelopathic effects on understory vegetation in P. massoniana pure forest and mixed forest, this study provided a new perspective to explain the understory vegetation status, and improve the vegetation structure and control soil erosion.

Key words: Magnolia grandiflora, resuspension, air pollution, Platanus acerifolia, ICP