南四湖湿地六种水生植物的磷素根际效应

Phosphorus rhizosphere effect of six wetland plants in field

利用根际土壤溶液的原位抽提和微量样品分析技术,对南四湖湿地的芦苇(Phragmites communis)、芦竹(Arundo donax)、香蒲(Typha latifolia)、水葱(Scirpus validus)、茭草(Zizania aquatica)和喜旱莲子草(Alternanthera philoxeroides)等6种水生植物进行了野外原位根际土壤溶液的磷素浓度分析,并从根系形态、磷素吸收利用有效性、根际土壤有效磷素和pH值变化等根际效应差异,揭示不同种类湿地植物磷素净化效率差异的内在机制.结果表明,香蒲对磷素的吸收最大;其次是芦苇、芦竹和茭草;再次是水葱和喜旱莲子草.香蒲的根际土壤溶液磷素浓度(PO43-,0.37μg/L)显著低于非根际区浓度(PO43-,0.47μg/L);而芦苇、芦竹和水葱则表现为根际土壤磷素浓度高于非根际.香蒲通过强大的根系获取了较多的磷素,芦竹则通过根际酸化促进了根系对磷素的吸收,实现了根际土壤较高的磷素去除率.喜旱莲子草根际土壤有效磷增加了48%,可能是由于其较强的根际酸化(pH值降低约0.9)增加了土壤磷素向水体流失的风险,故在湿地磷素修复中应避免使用.

In Nansihu wetland (China), micro-suction cups were used to collect samples of soil solution from the rhizosphere of six wetland plants roots (Phragmites communis, Arundo donax, Typha latifolia, Scirpus validus, Zizania aquatica and Alternanthera philoxeroides), and capillary electrophoresis was used to determine the phosphate concentration of the soil solution. Root morphology, phosphorus uptake efficiency and phosphorus utilization efficiency, and rhizosphere pH were also analyzed to reveal the mechanism of phosphorus retention. T. latifolia was the most effective in phosphorus retention, followed by P. communis, A. donax and S. validus. Phosphorus in the rhizosphere solution (PO_4^(3-), 0.37μg/L) was significantly lower than in the bulk soil solution (PO_4^(3-), 0.47μg/L) for T. latifolia, but was reversed for P. communis, A. donax, S. validus and A. philoxeroides; no significant difference was observed for Z. aquatica. This field study suggested that T. latifolia was efficient in phosphorus retention with a strong root system. For A. philoxeroides, available phosphorus (Olsen-P) was 50% higher for the rhizosphere soil than for the non-rhizosphere, and the rhizosphere acification and phosphorus mobilization were significant. It should be avoided for phosphorus retention in wetlands.