Abstract: Casuarnia equisetifolia is an important tree species for shelter belt at the seashores of South China, but it degenerates quickly. The potential cause of its degeneration is discussed from the viewpoint of allelopathly. The results show that allelochemicals produced by C. equisetifolia can inhibit the growth of its seedlings. Five allelochemicals from C. equisetifolia branchlet are isolated and identified by means of HPLC, IR and NMR. They are kaempferol-3-α-rhmanoside, quercetin-3-α-araboside, luteolin-3', 4'-dimethoxy-7-β-rhamnoside, kaempferol-3-β-dirhamnoside and quercetin-3-β-glucoside. The first three of them can inhibit the growth of seedling, and especially that of root.

Key words: Alleylopathy, Casuarnia equisetifola, Flavonids, Isolation and identification, seed-cotton yield, water and nitrogen use efficiency, water and nitrogen arrangement, dry matter accumulation, soil nitrate