关键词: 消落带, 淹水, 落羽杉实生苗, 实生土壤, 营养元素

Abstract:

Through simulated soil dynamic submergence in the hydro fluctuation belt of the Three Gorges Reservoir Region，four different kinds of water treatment were applied to examine the mechanism of the nutrient changes in soils of Taxodium distichum seedlings. The water treatments were normal growth water treatment (CK)，light drought water stress (T1)，soil water saturation treatment (T2) and soil submersion treatment (T3). The results showed that different water treatments had different effects on the nutrient contents of soils of T. distichum seedlings. During the entire experimental period，the mean content of organic matter did not exhibit significant difference between T1 and T2，and T3，which are respectively 5.8%，9.1% and 9.9% higher than in that of CK，highly significantly. Mean pH value in T2 was not significantly different from that in CK，in contrast to being 2.9% and 1.7% lower in T1 and T3 when compared to that in CK. Mean content of total nitrogen in T2 over the study period was significantly increased by 8.3% and 6.0% compared to that in CK and T1，respectively. Whereas，there was no significant difference to be found between T3 and CK，as well as between T3 and T1 in mean content of total nitrogen. Furthermore，the four groups did not differ from each other either in the mean content of total phosphorus or in the mean content of total potassium. The mean content of alkali hydrolysable nitrogen in T3 throughout the entire experiment was the highest among all the groups，being 15.3%，5.4% and 6.2% higher than in that of CK，T1 and T2，respectively. However，the mean content of available phosphorus and of available potassium in T1 was significantly higher than that in the other three groups，in which latter T2，T3 and CK did not differ from each other. The content of soil organic matter showed a highly positive relationship with the content of total nitrogen，the content of total phosphorus and the content of alkali hydrolysable nitrogen. On the other hand，pH value displayed a highly negative relationship with the content of alkali hydrolysable nitrogen and the content of available phosphorus. We found that T. distichum species can actively facilitate the restoration of the vegetation and the improvement of the soil conditions in the hydro fluctuation belt of the Three Gorges Reservoir Region.

Key words: hydro fluctuation belt, submergence, Taxodium distichum seedlings, growing soils, nutrient contents