Abstract: There is a difference in N and P contents of the leaves between nitrogen_fixing tr ees and no n_nitro g en_fix ing tree species.T he ex port rates of N and P from leaves are also differ ent between these two kinds of tr ees during leaf falling season.T he contents of N in foliage of the nitrog en_fix ing trees are 2 to 3 t imes hig her than that of the non_nitrogen fixing trees.T her e is slightly differ ence of P co n tents in the leaves betw een these two kinds of trees before and after leaf fallen.Befo re leaf fallen,ni trog en_fix ing tr ees,especially for non_leguminous N₂_fixing trees,had about 30% of N in the leaves transferred to trunk,branch and root and most of them(70%)retur ed to soil.T he regular partern of P export in foliag e is similar to Nex port during leaf falling season,var iation of the ex por t rates of P from leav es is between 40% to 60%.

Key words: water level fluctuating zone, soil seed bank, species composition, aboveground vegetation, environmental factor, Danjiangkou Reservoir.