Inter-Species and Inter-Organ Differences in Stable C and N Isotope Signatures of Macrophytes from the Largest Freshwater Lake in China

Abstract

Macrophytes play important roles in shallow aquatic ecosystems. Stable isotope signatures of macrophytes indicate the environmental conditions and macrophyte contributions to food webs. However, macrophyte isotope signatures have been studied less than isotope signatures of other organisms. We determined the stable C and N isotope signatures of 10 aquatic plant species from Poyang Lake wetland (Wucheng, Yongxiu County) and Nanji wetland (Nanjishan, Xinjian County) in Jiangxi Province, which are Chinese national nature reserves, among different seasons. The isotope signatures for different species and seasons were significantly different. The dominant macrophyte species were Potamogeton malaianus and Nymphoides peltatum. The isotope signatures for different organs of these two species were determined. Both δ13C and δ15N values were higher for P. malaianus than for N. peltatum stems, roots and leaves, and δ13C varied less for N. peltatum than for P. malaianus organs. The δ13C and δ15N values for P. malaianus organs increased in the order rootsstems>leaves, and δ15N values for N. peltatum organs increased in the order roots

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中国最大淡水湖大型植物稳定碳氮同位素特征的种间、器官间差异

大型植物在浅水生态系统中起着重要的作用。大型植物的稳定同位素特征表明环境条件和大型植物对食物网的贡献。然而，与其他生物的同位素特征相比，对大型植物同位素特征的研究较少。对中国国家级自然保护区江西省鄱阳湖湿地(永修武城)和南集湿地(新建县南集山)10种水生植物不同季节的稳定C、N同位素特征进行了测定。不同物种和季节的同位素特征有显著差异。优势植物种为马来马铃薯(Potamogeton malaianus)和peltatum。测定了两种不同器官的同位素特征。黄杨的δ13C和δ15N值均高于黄杨的茎、根和叶，黄杨的δ13C值变化小于黄杨的器官。malmalanus各器官的δ13C和δ15N值以根>叶的顺序增加，而N. peltatum各器官的δ15N值以根<茎<叶的顺序增加。malaianus和N. peltatum的稳定C和N同位素特征可能受大型植物生活史、外部C/N来源和湿地水量等多种因素的控制。这些结果为利用富水植物的δ13C和δ15N值检测湖泊中碳氮元素的流动趋势和环境变化提供了理论参考和实验数据支持。

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