Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, Box 7050, SE-750 07 Uppsala, Sweden.
Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, Box 7050, SE-750 07 Uppsala, Sweden.
Sci Total Environ. 2018 Sep 1;635:1436-1443. doi: 10.1016/j.scitotenv.2018.04.193. Epub 2018 Apr 25.
The importance of aquatic plant diversity in regulating nutrient cycling in wetlands remains poorly understood. We investigated how variation in macrophyte growth form (emerging, submerged and bryophyte) combinations and species mixtures affect nitrogen (N) removal from the water and N accumulation in plant biomass. We conducted a wetland mesocosm experiment for 100 days during July-September 2015. Twelve species were grown in mono- and in two-species mixed cultures for a total of 32 single and two-growth form combinations. Nitrogen removal from the water was quantified on three occasions during the experiment, while N accumulation in plant biomass was determined following termination of the experiment. The number of species and growth forms present increased N removal and accumulation. The growth form combinations of emerging and bryophyte species showed the highest N accumulation and N removal from water, followed by combinations of emerging species. By contrast, submerged species growing in the presence of emerging or other submerged species showed the lowest levels of N accumulation and N removal. Temporal variation in N removal also differed among growth form combinations: N removal was highest for emerging-bryophyte combinations in July, but peaked for the emerging-submerged and emerging-bryophyte combinations in August. Indeed, the occurrence of complementarity among macrophyte species, particularly in combinations of bryophyte and emerging species, enhanced N removal and uptake during the entire growing season. Our study highlights the importance of bryophytes, which have been neglected in research on nutrient cycling in wetlands, for aquatic N cycling, especially given their worldwide distribution across biomes. Overall, our findings point towards the potential important role of the diversity of macrophyte growth forms in regulating key ecosystem processes related to N cycling in wetlands.
水生植物多样性在调节湿地养分循环中的重要性仍知之甚少。我们研究了大型植物生长形式（挺水、沉水和苔藓）组合和物种组合的变化如何影响从水中去除氮（N）和氮在植物生物量中的积累。我们在 2015 年 7 月至 9 月期间进行了为期 100 天的湿地中观实验。12 个物种在单种和两种混合培养物中生长，共有 32 种单种和两种生长形式组合。在实验过程中进行了三次水中氮去除的定量，同时在实验结束后测定了植物生物量中氮的积累。存在的物种和生长形式的数量增加了氮的去除和积累。挺水和苔藓物种的生长形式组合表现出最高的氮积累和从水中去除氮，其次是挺水物种的组合。相比之下，在挺水或其他沉水物种存在下生长的沉水物种表现出最低的氮积累和从水中去除氮。生长形式组合的氮去除也随时间而变化：挺水-苔藓组合在 7 月氮去除率最高，但在 8 月挺水-沉水和挺水-苔藓组合氮去除率最高。事实上，大型植物物种之间的互补性发生，特别是在苔藓和挺水物种的组合中，增强了整个生长季节的氮去除和吸收。我们的研究强调了苔藓的重要性，苔藓在湿地养分循环研究中被忽视了，它们对水生氮循环很重要，特别是考虑到它们在全球范围内分布于各个生物群落。总的来说，我们的研究结果表明，大型植物生长形式的多样性在调节湿地与氮循环有关的关键生态过程方面具有潜在的重要作用。
