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题名: 云南异龙湖生态系统稳态转换过程与关键灾变因子反演研究
作者: 赵磊
学位类别: 博士
答辩日期: 2013
授予单位: 中国科学院研究生院
授予地点: 北京
导师: 朱永官
关键词: 异龙湖 ; Yilong Lake ; 稳态转换 ; regime shifts ; 水质-水生态模型 ; 驱动因子 ; 生态灾变
其他题名: The regime shifts and iversion of catastrophic driving factors in the ecosystems of Yilong lake, Yunnan
中文摘要:       浅水湖泊生态系统在环境及生物因子驱动下会发生稳态转换,在稳态转换前后,湖泊生态系统的内部结构和关键过程均会发生显著的变化,特别是灾变性稳态转换将会导致湖泊水环境在短时间内急剧恶化进而延缓和加大治理的进程及成本。探求浅水湖泊稳态转换驱动因子是科学合理确定湖泊管理策略的关键所在。本文以发生了灾变性稳态转换的浅水湖泊异龙湖为案例,以历史数据和沉积物硅藻记录分析异龙湖的生态系统演化和稳态转换过程,研发能够描述主要生态组分的生态模块并耦合至水质水动力模型,反演导致灾变性稳态转换的驱动因子。本文主要取得了以下结果:在我们具有观测数据的20年里,异龙湖在20世纪90年代初为藻草共存稳态,由于1992年至1996年取消网箱养鱼的原因,1996年异龙湖发生恢复性稳态转换,由藻草共存稳态转换为草型清水稳态;2009年由于鱼类过量放养的原因,异龙湖发生灾变性稳态转换,由草型清水稳态转换为浊水问题。2009年灾变性稳态转换过程表现为沉水植被大面积退化、蓝藻大规模爆发、Chla浓度激增,以及相应的氮磷营养盐浓度激增。历史数据显示,对应于异龙湖的3种稳态,异龙湖草型清水稳态的Chla浓度小于30μg/L,藻草共存稳态的Chla浓度介于30μg/L-90μg/L,浊水稳态的Chla浓度大于90μg/L。所对应的TP阈值为,当TP低于45μg/L时湖泊保持为清水状态,总磷高于90μg/L湖泊为浊水稳态。研发了能够描述营养物质、光照、温度、自遮光、呼吸、鱼类捕食等过程对沉水植物生长消亡影响的生态模块,并将该模块与EFDC模型耦合,形成了统一在一个集成的数学方程体系内的沉水植被动力学、浮游藻类、湖泊底质生物地球化学反应动力学及水体内营养盐的迁移转化动力学的集成模型。基于研发完成的模型平台构建了异龙湖三维水质-水生态-水动力模型,证实了鱼类放养是异龙湖2009年灾变性稳态转换的直接驱动因子,而单纯的氮磷负荷增加会引起湖泊营养水平增加,在水生植物覆盖度、生物量并无明显消退的情况下引起藻类生物量增加,使得湖泊处于藻草共存稳态,但不会导致湖泊转换为浊水稳态。然而,当负荷与鱼类放养共同起作用时,负荷与鱼类放养将会有明显的耦合作用,将会诱发比2009年强度更大的生态系统灾变性稳态转换。为促进异龙湖由浊水稳态转换为清水稳态,异龙湖的外源性氮磷负荷需要削减77%的现状负荷,通过负荷削减并控制鱼类放养能够有效降低湖泊的营养盐水平进而控制藻类爆发。
英文摘要:       Regime shifts of the shallow lake ecosystem can happen under environmental and biological driving factors. Before and after regime shifts, the structure and key process will change dramatically, especially the catastrophic regime shifts can cause lake water environment to deteriorate sharply in a short period of time and defer the process of restoration. Revealing the driving factors of regime shifts is the key to make scientific management of shallow lakes. Yilong Lake turned turbid state with sudden sharp increase in Chlorophyll a (Chl a) in 2009 without apparent change in external loading levels. Time series data and sediment diatom records were analysed to investigate the evolution of lake ecosystem and process of regime shifts., Ecological module coupling with water quality and hydrodynamic mode were developed, simulating the flow circulation, pollutant fate and transport, and the interaction between nutrients, phytoplankton and macrophytes, to investigate the driving factors as well as examining the underlying mechanism of the catastrophic regime shifts.In the past decades, Yilong Lake have shifted twice among a state of clear state with algae and vegetation, a state of clear with abundant macrophytes, a state of turbid with spase macrophytes. Yilong Lake was in “algae- macrophytes” regime in 1990s and shifted to clear state in 1996. The cause of this shift may be the result of forbidden of cage culture. Yilong Lake was in a state of clear from 1996 to 2008 and shifted to turbid state in 2009. The cause of this shift may be the result of inappropriate fish stocking. The catastrophic regime shift in 2009 followed a decline of submerged macrophytes, increase of Chla, total nitrogen (TN) and total phosphorus (TP) concentration. The Chla concentration of different state of Yilong Lake is different. In macrophytes-dominated clear state, Chla concentration was below 30μg/L. In “algae-macrophytes”-dominated state, Chla concentration was 30μg/L-90μg/L. In algae-dominated state, Chla concentration was beyond 90μg/L. The threshold of TP was 45μg/L in the shift from algae-dominated state to macrophytes-dominated state, and the threshold of TP was 90μg/L in the shift from macrophytes-dominated state to algae-dominated state.We developed a ecological module that can simulate dynamics of submerged macrophytes. The factors that we considered is nutrient, light, temperature, self-shading, respiration, and fish grazing. We coupled this module with EFDC (Environmental Fluid Dynamics Code) model and developed a integrated mathematical equations which can describe submerged macrophytes dynamics, algae dynamics, sediment biogeochemistry and nutrient transformation kinetics. Based on calibrated three-dimensional water quality and aquatic ecology model, we conducted four sets of scenarios for understanding the driving factors of the catastrophic regime shifts. We confirmed that inappropriate fish stocking was the direct driving factor of the catastrophic regime shifts in 2009. The simple increase of nutrient load without fish stocking could increase the concentration of nutrient in lake and shift the lake from macrophyte-dominated clear state to “algae-macrophytes”-dominated state without apparent decline of submerged macrophytes. But the simple increase of nutrient load could not shift the lake from macrophyte-dominated clear state to algae-dominated state. The increase of nutrient load with fish stocking could induce more serious catastrophic regime shifts than 2009. To restore the Yilong Lake from turbid state to clear state, the watershed reduction ratio would need to be 77%. With the effort of load reduction and control of fish stocking we can reduce the nutrient concentration and algae bloom.
内容类型: 学位论文
URI标识: http://ir.rcees.ac.cn/handle/311016/35189
Appears in Collections:中澳联合土壤环境研究室_学位论文

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Recommended Citation:
赵磊. 云南异龙湖生态系统稳态转换过程与关键灾变因子反演研究[D]. 北京. 中国科学院研究生院. 2013.
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