鄱阳湖洲滩典型湿地植物的水位生态幅研究

Beach vegetation is an important component of the wetland ecosystems maintaining of wetland ecosystem stability in Poyang Lake. Seasonal fluctuation of water level is a crucial factor influencing the growth,distribution, and dynamic process of beach wetland plant. This study applied field investigation and simulation of water level seasonal fluctuation to probe the physiological and ecological indexes in the process of life history of the largely typical plants. These plants are widely distributed on the beach wetland such as Phragmites australis, Triarrhena lutarioriparia, Carex cinerascens and Acorus calamus, quantitative analysis the appropriate level, tolerance range, and endurance time of beach wetland dominant plants in Poyang Lake at different growth stages. In addition, the study aims to explore the process and mechanism of wetland plants in response to water level changes, and to reveal the relationship between water level and the wetland plants. The ecological model of wetland was established and effects of water level / elevation on the life history of typical plant of beach wetland was simulated according to the investigation and test data. Moreover, the basis for quantitative analysis was founded and the wetland ecological condition was simulated. The research results would benefit to reveal the complex relationship between the wetland plants and water level, and the temporal and spatial distribution of wetland plants under the conditions of water level variation. It can also provide a theoretical basis for calculations of ecological water demand in wetland ecosystem, which in favor of scientific management, reasonable protection, and ecological restoration of lakes and wetlands.

洲滩植物是鄱阳湖湿地生态系统的重要组分，在维持生态系统结构和功能方面发挥着重要作用。季节性水位变化是影响鄱阳湖洲滩湿地植物生长发育、分布及动态过程的关键因子。本研究拟通过野外观测及模拟水位季节性动态变化研究洲滩湿地分布较广、面积较大的典型植物芦苇、南荻、灰化苔草、菖蒲等植物生活史过程中的生理生态学特征，定量分析鄱阳湖洲滩湿地典型植物在不同生长发育阶段的适宜水位及对水位的耐受范围和持续耐受时间，探索湿地植物对逆境（夏季长期淹水及冬春季持续干旱）条件的适应机理，揭示水位与湿地植物生长发育过程之间的相互关系。根据研究数据建立生态模型，模拟研究水位/高程对洲滩湿地典型植物生活史过程的动态影响，预测水文过程对湿地植物的影响及程度。研究结果有助于揭示水位动态变化条件下湿地植物的时空分布规律，为特定条件下湿地生态系统的生态需水量的计算提供理论依据，有利于湖泊湿地的科学管理、合理保护及生态恢复。

本项目基于野外调查及试验基地观测，模拟鄱阳湖水位季节性变化规律， 研究水位变化对分布较广、面积较大的典型湿地植物灰化苔草、虉草、苦草、狗牙根、菖蒲和菹草等的生长发育过程的影响，阐明了水位变化对湿地植物的影响及湿地植物对水位动态变化的生理生态适应机理，揭示了典型湿地植物的水位生态幅。主要结论如下：.（1）鄱阳湖洲滩湿地植物优势物种主要有灰化苔草、虉草、狗牙根、蓼子草、蚕茧蓼、下江委陵菜、芦苇、水蓼、具刚毛荸荠、水田碎米荠等；.（2）灰化苔草根状茎萌发及幼苗生长的水分生态幅在4.15%~51.34%范围内，最适水分含量在16.22%~39.54%之间。淹水胁迫会抑制灰化苔草幼苗生长，表现为株高降低，叶缘发黄损坏；淹水对灰化苔草根茎的萌发也有影响，适度的淹水有利于灰化苔草根茎的萌发； 淹水导致灰化苔草幼苗叶片的相对叶绿素含量降低，抑制其光合作用；.（3）虉草的水分生态幅为[7.48%，52.20%]，最适水分生态幅为[18.99%，40.60%]。淹水胁迫会对虉草造成伤害，主要表现为生长速度减缓、体内活性氧增加、抗氧化酶保护系统受到破坏、膜脂过氧化程度加剧、植株逐渐死亡；.（4）苦草株高随水深增加总体呈增加趋势，130cm处的苦草平均高度最大； SOD、POD活性均随水深的增加不断降低。在透明度较好的水域生态恢复中应考虑在100~140cm的水深范围内恢复苦草种群；.（5）狗牙根匍匐茎萌发及幼苗的最适土壤水分生态幅为[14.78%，30.15%]，极限生态幅为[5.65%，38.26%]，水分含量对狗牙根匍匐茎萌发幼苗的单株生物量和平均叶片长度影响最为显著；.（6）菖蒲生长的最适点水位位于水下[18.8， 49.6]cm处左右，菖蒲生长的极限水位为[-52.3，141.8] cm，大于141.8cm和小于-52.3cm的水位无法满足菖蒲的正常生长和发育。轻度干旱会导致菖蒲地上生物量降低，持续干旱条件下会使菖蒲叶片PSII系统遭到不同程度的破坏；.（7）自然光照的20%-60%条件下菹草生长状况较好；持续的弱光胁迫将导致植物活性氧代谢失调，细胞受到伤害，最终导致植物死亡。