异龙湖草型-藻型稳态转换的有机碳氮及其同位素源解析  

Source partitioning of organic carbon and nitrogen and associated isotopic signal change due to macrophyte-to algae-dominated stage transformation of Yilong Lake

作　　者：杨关绍 王旭 郭雯 王明果 温雯雯[1] 孔令阳 黄林培[1] 陈光杰[1] YANG Guanshao;WANG Xu;GUOWen;WANG Mingguo;WENWenwen;KONG Lingyang;HUANG Linpei;CHEN Guangjie(Yunnan Key Laboratory of Plateau Geographic Processes and Environmental Change,Faculty of Geography,Yunnan Normal University,Kunming 650500,China;Meteorological Bureau of Fengning Manchu Autonomous County,Chengde 068350,Hebei,China;Yunnan Geological Mine Mapping Academy Co.,Ltd,Kunming 650217,China)

机构地区：[1]云南师范大学地理学部,云南省高原地理过程与环境变化重点实验室,昆明650500 [2]河北省丰宁满族自治县气象局,承德068350 [3]云南省地矿测绘院有限公司,昆明650217

出　　处：《地理研究》2023年第11期3061-3078,共18页Geographical Research

基　　金：国家自然科学基金项目(42067064、42171072);云南省重点研发计划项目(202203AC100002-02);云南省院士专家工作站项目(202005AF150005、2017IC063);异龙湖高原浅水湖泊云南省野外科学观测研究站项目(202305AM070002)。

摘　　要：湖泊稳态转换导致湖泊由清水态向浊水态转变,不仅削弱湖泊生态系统功能和服务,同时会对湖泊有机质来源组成及碳氮循环过程产生显著影响。本研究采集了异龙湖20根短钻岩芯,对沉积物有机质的碳氮稳定同位素及C/N值进行测定,根据指标变化模式并结合前人研究结果,识别了异龙湖稳态转变前后草型阶段和藻型阶段两个时期。结果显示,沉积物δ^(15)N值较低(2.50‰±1.42‰),与化肥氮同位素信号相近,表明长期的农业面源污染是导致异龙湖水体富营养化的主要原因。近百年来异龙湖从草型清水态向藻型浊水态的转变过程中,呈现碳同位素信号偏负、C/N值较低的藻源性有机质来源占比升高而水生维管束植物(δ^(13)C偏正,C/N值较高)来源降低的演变过程。进一步运用MixSIAR贝叶斯混合模型对异龙湖草型、藻型两个时期有机质来源的定量分析表明,浮游植物贡献率从草型湖泊阶段的26.69%±4.38%上升到藻型湖泊阶段的41.91%±5.03%;而沉水植物贡献率则由16.10%±6.26%下降到2.89%±1.09%。此外,较高的陆源有机质占比(草型:39.6%±3.5%,藻型:37.3%±3.4%),可能与较大的异龙湖流域与湖泊面积比(11.63)以及流域土地利用类型改变导致的地表侵蚀速率上升有关。草型和藻型阶段中挺水植物的相对贡献率没有显著差异(17.60%±1.87%和17.93%±1.62%),指示浅水湖泊湖滨带挺水植物分布广泛,受水体营养水平的影响较小;同时挺水植物纤维素含量高、降解速度慢,更容易在沉积物中保存,成为沉积物有机质的重要来源之一。湖泊生态系统稳态转换过程中有机质来源的定量研究有助于精准甄别不同有机质贡献情况,为制定湖泊管理策略与实施评估提供帮助,为生态修复提供理论支撑。Regime shifts in shallow lakes(clear state to turbid state)lead to reductions in functions and services of lake ecosystems.These transformations also affect sources of lake organic matter and the cycling of carbon and nitrogen.In this study,20 sediment cores from Yilong Lake were collected to measure carbon and nitrogen stable isotopes and C/N ratios.Based on the background knowledge on variation of multiple indexes,the macrophyte-and algae-dominated stages of Yilong Lake were identified.Results showed that sedimentδ^(15)N was low(2.50‰±1.42‰),close to the isotope signal of nitrogen fertilizer,indicating that long-term agricultural non-point source pollution was the most important cause for the eutrophication of Yilong Lake.In addition,during the regime shifts in Yilong Lake,the proportion of algal source characterized by negative carbon isotope signals and low C/N ratios increased,in contrast to an increased proportion in macrophyte source(δ^(13)C is positive and C/N ratio is high).Further quantitative analysis by using the MixSIAR Bayesian mixing model showed that the contribution of algae source increased from 26.69%±4.38%in the macrophyte-dominated lake stage to 41.91%±5.03%in the algae-dominated lake stage.However,the contribution of submerged macrophyte decreased from 16.10%±6.26%to 2.89%±1.09%.Furthermore,higher proportion of terrestrial organic matter(39.6%±3.5%in macrophyte-dominated lake and 37.3%±3.4%in algae-dominated lake)might be related to the high ratio of catchment area to lake area(11.63)and the increase of surface erosion rate caused by the change in land use.The contributions of emergent plants in two stages were 17.60%±1.87%(macrophyte-dominated lake)and 17.93%±1.62%(algae-dominated lake),respectively,suggesting emergent plants were less affected by eutrophication and thus widely distributed in the riparian zone of Yilong Lake in both stages.Additionally,the cellulose of emergent plants was high,degraded slowly,and was easier to preserve in lake sediment and became one of the m

关 键 词：草型和藻型湖泊 碳氮稳定同位素 沉积物有机质 定量化 异龙湖 

分 类 号：X524[环境科学与工程—环境工程]