EFFECTS OF DIFFERENT WATER TREATMENT ON THE NUTRIENT CONTENTS IN SOILS OF TAXODIUM ASCENDENS SEEDLINGS

Through simulating soil dynamic submergence in the hydro-fluctuation belt of the Three Gorges Reservoir Region, four different kinds of water treatments were applied to examine themechanism of the nutrient change in soils of Taxodium ascendens seedlings.The water treatments were normal growth water treatment (CK), light drought water stress (T1), soil water saturat ion treatment (T2) and soil submersion treatment (T3).Different water treatments had different effects on nutrient contents in soils of T.ascendens seedlings.During the entire experimental period, the mean content of organic matter in T3 was 912%, 516% and 614%, which was significantly higher than that in CK, T1 andT2, respectively, while no significant differences were found among T1, T2 and CK1Mean pH value in T2 and T3 was significantly higher than that in CK with 310%) 1018% and 411%) 715% respectively, however, T2 did not differ from T3 in mean pH value.Mean content of total nitrogen in T3 over the study period was significantly increased by 819%, 518% and 910% compared with that in CK, T1 and T2, respect ively, in wich the latter three groups did not exhibit significant difference between each other1There was no significant difference found among the four groups either in mean content of total phosphorus or mean content of total potassium1Likewise, mean content of alkali hydrolysable nitrogen in T3 exceeded by 1315%, 711% and 617% over that in CK, T1 andT2.T1 did not demonstrate a significant difference with T2, but both T1 and T2 showed a significantly higher content compared to CK, in mean content of alkali hydrolysable nitrogen.T2 and T3 showed significantly lower value than T1 and CK in mean content of available phosphorus.In contrast, T1 and T2 were significantly higher than T3 and CK in mean content of available potassium.Content of soil organic matter showed a highly positive relationship with the content of total nitrogen, content of total phosphorus and content of alkali hydrolysable nitrogen, in contrast to its highly negative relationship with the content of available phosphorus.The change of nutrient contents in soils of Taxodium ascendens seedlings under different water conditions showed that Taxodium ascendens species could be selected for building a forest protection system in the hydro-fluctuation belt of the Three Gorges Reservoir Region.