【摘要】 为研究在浅水湖泊的外源污染源控制工作中控氮（N）的必要性,通过室外模拟实验,探究了N负荷升高对浅水湖泊沉水植物生长的影响。实验设置低N组（输入氮磷比为5∶1）和高N组（输入氮磷比为100∶1）两个N负荷水平,同时选择不同生长型的两种沉水植物——莲座型苦草（Vallisneria natans）和冠层型穗花狐尾藻（Myriophyllum spicatum）作为实验对象。结果表明:N负荷升高对苦草生长产生了明显的抑制作用,表现为高N组苦草的相对生长率、生物量、根长、株数和叶片数等指标均显著低于低N组。与苦草不同,N负荷升高对穗花狐尾藻的胁迫作用不显著,两种N浓度下穗花狐尾藻的生物量、相对生长率、节间距、株高和株数均无明显差异。总体而言,N负荷升高显著降低了沉水植物的总生物量,实验结束时高N组沉水植物的总生物量(115.86 g?m^-2)是低N组(321.98 g?m^-2)的36.0%。研究表明,N负荷升高会对沉水植物的生长产生胁迫,但是不同沉水植物对N负荷升高的响应具有种间差异。从湖泊管理和生态修复的角度,本研究支持外源N、P均需要控制的观点。更多还原

【Abstract】 N and P are key factors that limit phytoplankton growth in freshwater lakes. Controlling external P loading is a widely recognized measure for lake restoration, but the necessity of limiting N inputs remains under debate. Here, we conducted a mesocosm experiment with a duration of 28 d to explore the effects of external N loading on the growth of submerged macrophytes with contrasting growth types of rosette（Vallisneria natans）and canopy（Myriophyllum spicatum）. There were mixed plantings of both macrophytes（density ratio:1∶1）in each mesocosm. Our experiment design included one treatment with two levels of N inputs（high N group:N∶P=100∶1; low N group:N∶P=5∶1）. The results showed that high N inputs greatly inhibited the growth of V. natans, which had a significantly lower relative growth rate,biomass, root length, and number of plants and leaves in the high N group compared with those in the low N group. However, there were no significant differences in the relative growth rate, biomass, internodal length, total height, and number of plants of M. spicatum between the two N loading treatments, thereby indicating that N loading did not have a significant effect on the growth of M. spicatum. Overall, the total biomass of the two submerged macrophytes in the high N group(115.86 g?m^-2)was only 36.0% of that in the low N group(321.98 g?m^-2),thereby indicating that high external N loading had a significant negative effect on submerged macrophytes. Our study suggested that high N inputs can greatly reduce submerged macrophytes in shallow lakes, but the effects are species-specific. From the perspective of lake management and restoration, our study supported the view that both N and P should be controlled.更多还原