泛洪深度和持续时间对刺苦草繁殖分配及营养繁殖体特征的影响

The water level fluctuation has a significant impact on submerged plants in the lacustrine ecosystems that linking to the river. The reproductive response of Vallisneria spinulosa to water level fluctuation is critical to vegetation restoration and food source of wintering birds in the mid-lower Yangtze lakes. In order to discuss the reproductive adaptability of submerged plant to water level fluctuation in the lakes that linking to the river, the project will take advantage of V. spinulosa as object, which is a dominant species of submerged plant in Poyang Lake-the largest lake that linking to the river in China. Tubers and seeds will be grown synchronously under different flooding depth and flooding duration treatments by stimulating the characteristics of water level fluctuation in Poyang Lake in a controlled experiment. This project arms to study: 1) the reproductive allocation of V. spinulosa in response to flooding depth and duration, 2) the effects of flooding depth and duration on shaping vegetative propagule characteristics, 3) the differences in reproductive allocation and vegetative propagule characteristics in seed- and tuber-derived plants. The project arms to reveal the fact that how V. spinulosa enhances its fitness in the habitat by tuning biomass allocation among plant parts, C and N allocation patterns, the relationships between vegetative growth and reproduction, and trade-offs between sexual and vegetative reproductive allocation, as well as tuber characteristics. We will discuss the effects of different reproductive modes to plant fitness and population restoration. The objective changing pattern of reproductive adaptability of V. spinulosa in response to water level fluctuation can be illustrated. This study can provide a basis for restoration and scientific management of submerged plant populations in Poyang Lake and even in the middle and lower reaches of the Yangtze River Basin.

水位变化对通江湖泊生态系统中沉水植物有重要影响。刺苦草对水位变化的繁殖响应是长江中下游湖泊植被恢复及越冬水鸟食物来源的关键。本项目以我国最大的通江湖泊鄱阳湖优势沉水植物刺苦草为对象，以块茎和种子为材料同步萌发生长，探讨通江湖泊沉水植物应对水位变化的繁殖适应对策。通过受控实验模拟鄱阳湖水位变化的特点，以不同泛洪深度和持续时间为共同处理手段，研究：1）刺苦草繁殖分配对泛洪深度和持续时间的响应；2）泛洪深度和持续时间对营养繁殖体特征的塑造作用；3）种子-植株和克隆-植株之间繁殖分配及营养繁殖体特征的差异。本项目旨在揭示刺苦草如何通过调整不同器官生物量分配、C和N分配、营养生长与繁殖及有性繁殖与无性繁殖之间的关系来提高其在生境中的适合度，探讨不同繁殖方式对植物适合度及种群恢复的影响，阐明刺苦草繁殖适应性响应水位变化的客观规律，将为鄱阳湖乃至长江中下游流域中主要沉水植物种群恢复和科学管理提供依据。

沉水植物对水生生态系统结构和功能的稳定有着重要的作用，水位变化对通江湖泊生态系统中沉水植物的生长、繁殖和进化演替有重要影响。本项目选择我国最大的通江湖泊鄱阳湖优势沉水植物苦草和刺苦草为对象，通过野外控制实验方法，探讨通江湖泊沉水植物应对水深梯度变化的繁殖适应对策。结果表明：1) 在不同水深梯度下，苦草的有性繁殖和营养生长是高度可变的，繁殖和营养生长之间存在此消彼长的权衡关系；2) 水深过高或过低时，苦草植株由于开花、结实要付出更高的繁殖代价，从而不可避免对营养生长产生负面影响；3) 在较高或较低的水深条件下，苦草植株降低营养生长资源分配，而增加繁殖资源分配；4) 不同水深条件下苦草植株的有性繁殖生物量表现出显著不同的异速生长关系，苦草对水深变化表现出明显的有利于提高其适应能力的可塑性响应； 5) 深水和浅水环境中刺苦草的种子产量减少，但冬芽产量增加，繁殖方式由有性繁殖向无性繁殖转变；6) 刺苦草无性与有性繁殖生物量分配与水深密切相关，并受个体大小制约，对水深的可塑性强；7) 深水和浅水环境显著降低了生物量对有性繁殖的分配，但却增加了对无性繁殖的分配；8) 刺苦草无性繁殖与有性繁殖之间存在权衡关系，是保证物种繁衍的“两头下注”对策，最终将影响种群的消长。上述结果初步揭示了两种苦草属植物生长、繁殖、分配等生活史对策沿着水深梯度的变异，为进一步探讨水位变化过程中沉水植物的演变与适应机制提供了科学依据，,为长江中下游流域浅水湖泊中主要沉水植物的恢复与管理提供理论指导。发表论文6篇，其中4篇被SCI收录，2篇发表在国内核心刊物。