苦草生长对沉积物中磷迁移转化的影响

构建了不同营养盐负荷的沉积物环境"水-苦草-沉积物"生态系统,监测分析了沉积物中总磷(TP)、生物可获得磷及其环境因子的垂直分布及变化,以苦草为例,研究了沉水植物生长对沉积物中磷迁移转化的影响,结果表明:生长期的苦草通过改变沉积物环境因子或自身的生理活动,直接或间接地对沉积物中不同形态磷的迁移转化产生了影响,并随着深度的增加而出现不同的变化。具体表现在,低(L)、中(M)、高(H)营养负荷的沉积物总磷(TP),相对于初始值均有不同程度的下降,但苦草组下降的幅度大,分别比对照组多下降了11.63、18.50和46.25 mg/kg;在垂直方向上均表现出随深度的增加TP呈减少趋势,苦草对沉积物影响的深度随根系的活动范围变化而变化,根系增长最长(比试验初始增加了9.2 cm)的低营养负荷苦草组(LV),可影响到6 cm以下的沉积物;中营养负荷苦草组(MV)、高营养负荷苦草组(HV)根系增加不明显(分别为2.60和2.10 cm),影响深度主要在6 cm以内;检验发现,苦草组与对照组差异显著(P0.05)。交换态磷(Ex-P)、铝磷(Al-P)随深度增加而升高,苦草组小于对照组;铁磷(Fe-P),随深度的增加而降低,苦草组大于对照组,其中,在L、M、H中,苦草组的Ex-P分别比对照组下降了0.065、0.215和1.483 mg/kg,Al-P分别为1.198、2.040和2.390 mg/kg;LV中苦草的影响深度可达到10 cm的深,而MV、HV中主要集中在6 cm以内;苦草组中的Fe-P分别比对照组高8.135、16.689和8.598 mg/kg,在垂直方向上的变化幅度亦大于对照组。检验发现,L中苦草组Ex-P与对照组有极显著差异(P0.01),M、H苦草组与对照组无显著差异(P0.05);L、M、H中Al-P、FeP苦草组与对照组均无显著差异(P0.05)。

Effects on the transformation of phosphorus in sediment with growing of Vallisneria natans

Phosphorus is a very important limiting factor in nutrient cycling. Sediments act as both sinks and sources of phosphorus due to continuous transport of chemical species across the sediment-water interface. The submerged macrophyte has an important influence on the migration and transformation of phosphorus in sediments. In order to investigate the impact of the macrophyte on the transformation of phosphorus in sediment, Vallisneria natans was taken as an example, and the ecological system of water-Vallisneria natans-sediment was constructed in different nutrient levels of sediments. The variations of phosphorus and environmental factors were measured during the growing season of Vallisneria natans. The result showed that Vallisneria natans directly and indirectly influenced the migration and transformation of different phosphorus forms in different degree. In addition, the transformation of phosphorus showed different variation tendencies as the sediments depth increased. In oligotrophic sediment (L), moderate eutrophic sediment (M) and eutrophic sediment (H), total phosphorus (TP) showed decreasing trends at various levels. However, the decreasing rate of TP in Vallisneria natans group was larger than that of the control group, and they had, on average, decreased more 11.63, 18.50 and 46.25 mg/kg than the control group, respectively. TP had a decreasing trend with increasing depth. The extent and influence of Vallisneria natans on sediment depended on the range of its root action. In oligotrophic sediment and Vallisneria natans group (LÜ), the root length increased 9.2 cm than the initial value, and it could affect the sediment depth over 6 cm. But they affected the sediments depth within 6cm because they didn''t increase significantly in the root length. There was a significant difference between Vallisneria natans group and the control group (P < 0.05). Exchangeable-phosphorus (Ex-P) and aluminum bound phosphorus (Al-P) of Vallisneria natans group increased with increasing depth, and they were lower than those of the control group in L, M and H. Moreover, the extent of variation in Vallisneria natans group was significantly greater than that of the controls (P <0.05). Iron bound phosphorus (Fe-P) decreased with increasing depth. Fe-P of Vallisneria natans group was higher than that of the control group in vertical direction. Ex-P had, on average, decreased more 0.065, 0.215 and 1.483 mg/kg than the control group, respectively. Meanwhile Al-P had on average, decreased more 1.198, 2.040 and 2.390 mg/kg than the control group, respectively. But Fe-P had, on average, increased more 8.135, 16.689 and 8.598 mg/kg than the control group, respectively. Vallisneria natans affected the sediment depth to 10 cm in LÜ. But it affected the depth within 6 cm in moderate eutrophic sediment and Vallisneria natans group (MV) and eutrophic sediment and Vallisneria natans group (HV). As for Ex-p, there was an significant difference between Vallisneria natans group and the control group in L (P < 0.01), but there were no significant differences in others (P > 0.05). As for Al-P and Fe-P, there were no significant differences in L, M and H (P > 0.05).