| 摘要: |
| 在极端水文事件频发和人类活动影响加剧的背景下，鄱阳湖水文情势的异常变动给洲滩湿地植物带来了一系列影响。为进一步了解鄱阳湖湿地植物水分利用来源和内在水分利用效率（iWUE）的季节变化规律，揭示优势植物在生长过程中对不同水分变化的适应策略，于2020年12月—2021年5月在鄱阳湖国家级自然保护区蚌湖和修河之间的典型洲滩湿地上设置监测断面，对灰化苔草（Carex cinerascens）、南荻（Triarrhena lutarioriparia）植物样品及其潜在水源样品进行系统采集，测定并分析了水、碳稳定同位素的动态变化特征和指示意义。结果表明，典型洲滩湿地苔草和南荻植物茎水的氢、氧稳定同位素组成没有表现出明显差异，从冬季至春季，植物茎水的δ18O值总体上均呈现波动富集的变化趋势。苔草在春季生长期iWUE没有表现出明显变化，而南荻在萌发时期iWUE最低，之后的生长期iWUE具有显著的增长趋势。在各潜在水源当中，植物茎水的同位素组成与土层中的重力水最为相近，其次为与根系分布联系密切的土壤水。在春季降水频繁时，来源于降水且埋深较浅的重力水可能是植物利用的主要水源，而在枯水期重力水埋深较深时，植物采取降水和土壤水的混合利用模式应对水分胁迫。植物叶片有机质的δ18O值分析发现，苔草在萌发生长期iWUE的变化与光合作用能力相关的因素有关，南荻iWUE的变化主要受气孔导度变化的影响。 |
| 关键词: 稳定同位素 植物水分来源 内在水分利用效率 叶片有机质 湿地生态系统 |
| DOI： |
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| 基金项目:国家自然科学基金项目（重点项目，青年项目） |
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| Variations of water, carbon isotopic characteristics and intrinsic water use efficiency of vegetation in the typical beach wetland of Lake Poyang, China |
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TAO Shiyong1, ZHANG Xiang1, XIA Junqiang1, LIU Haoyuan1, XU Jing1, XIONG Xingji1, XIAO Yang2
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1.State Key Laboratory of Water Resources Engineering and Management, Wuhan University;2.Changjiang Water Resources Protection Institute
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| Abstract: |
| As the largest freshwater lake in China, Lake Poyang has the most abundant biological resources among China’s wetland ecosystems. Under the context of frequent extreme hydrological events and intensified impacts of human activities, the abnormal variation of hydrological regime in Lake Poyang has brought diverse effects on the vegetation in the beach wetlands, which further aggravates the vulnerability of wetland ecosystem. Therefore, it is needed to understand the seasonal variations of water use sources and intrinsic water use efficiency (iWUE) of the vegetation in the beach wetlands, and to reveal the adaptive strategies of dominant vegetation to water changes during the growing period. A beach wetland in the Lake Poyang National Nature Reserve (between Lake Banghu and Xiuhe River) was selected as the study area, due to its typical vegetation community, ecosystem structure and ecohydrological characteristics. A systematic sampling of Carex cinerascens and Triarrhena lutarioriparia, as well as their potential water sources was carried out from December 2020 to May 2021. The stable isotopic characteristics of water and carbon were analyzed for their temporal variations and indicative significance. Our investigation showed no significant difference in the stable isotopic compositions of hydrogen and oxygen between the stem water of Carex cinerascens and Triarrhena lutarioriparia in the typical beach wetland. From winter to spring, the δ18O values of plant stem water showed a fluctuating and enriching trend. The iWUE of Carex cinerascens showed no significant variation during the spring growing period, while the iWUE of Triarrhena lutarioriparia was the lowest at the germination period and subsequently showed a significant increasing trend at the growing period. The isotopic composition of plant stem water was most similar to that of the gravitational water in the soil layer among the potential water sources, followed by the soil water. In the case of frequent precipitation in spring, the gravitational water with shallow depth from precipitation may be the main water source for vegetation utilization. When the gravitational water storage was relatively deep in the dry season, the vegetation adopted a mixture of precipitation and soil water to survive with the water stress. Combined with the δ18O values of plant leaf organic matter, the variation of the iWUE of Carex cinerascens during the germination and growing period was related to the plant photosynthetic capacity. The variation of the iWUE of Triarrhena lutarioriparia was mainly affected by the changes of stomatal conductance. |
| Key words: Stable isotope Plant water source Intrinsic water use efficiency Leaf organic matter Wetland ecosystem |
