【作者】 李伟；

【导师】 袁琳；

【作者基本信息】 华东师范大学 ， 生态学， 2018， 硕士

【摘要】 滨海湿地是海陆交汇的生态过渡带,在维持栖息地的生态平衡及调节碳循环等方面发挥着重要作用,是自然界最具生产力的生态系统之一。盐沼作为滨海湿地重要的组成部分,具有较高的初级生产力,在调节气候、净化水质和维护海岸线等方面扮演着重要角色,对于湿地生态系统的维持具有重要作用。淹水及盐度作为滨海湿地的主要环境因子,影响着盐沼植物的存活、生长及分布。然而,未来海平面上升可能引起淹水胁迫及盐水入侵,将使滨海湿地盐沼植物水-盐胁迫更加严峻,进而影响滨海湿地生态系统的结构和功能。当水-盐胁迫较小时,生态系统通过自我调节可维持在某个稳定状态,一旦扰动超过盐沼植物的存活阈值(Threshold),将会引起生态系统发生不可逆的变化,导致生态系统的结构和功能发生改变,严重影响生态系统的稳定性和可持续发展。因此,若能在系统出现重大变化之前,开展滨海湿地典型盐沼植物对于水-盐胁迫的响应及阈值研究,预测并采取有效的管理手段,对于滨海湿地生态修复工程的开展、生态系统保护及可持续管理而言具有重要意义。本研究选取长江口滨海湿地典型盐沼植物海三棱藨草(Scirpus mariqueter)、互花米草(Spartina alterniflora)和芦苇(Phragmites australis)为研究对象,于上海市南汇东滩开展高程模拟实验,于温室内开展模拟盐胁迫及水-盐交互胁迫的人工控制实验,定期监测并分析三种盐沼植物的存活率、株高、分蘖数及结穗率,生长季末测定地上及地下部生物量,并分别获取三种盐沼植物在高程、盐胁迫及水盐交互胁迫下的存活阈值,以探讨水-盐胁迫对三种盐沼植物存活、生长和繁殖的影响。主要研究结果如下:1.长江口典型盐沼植物对高程的响应及阈值(1)海三棱藨草、互花米草和芦苇的株高、分蘖数及地上生物量均随着高程的增加呈先增加后下降的趋势,分别在高程为2.80 m、2.96 m及3.30 m时分蘖数量最多,地上生物量最大。(2)三种长江口典型盐沼植物高程阈值大小依次为:海三棱藨草(2.36 m)<互花米草(2.51 m)<芦苇(2.79 m),即高程分别低于该阈值时,三种盐沼植物不能有效存活;日均持续淹水时间阈值大小依次为:海三棱藨草(6.25 h/d)>互花米草(6.00 h/d)>芦苇(5.33 h/d),即日均持续淹水时间高于该阈值时,三种盐沼植物不能有效存活。(3)海三棱藨草、互花米草和芦苇的最适生境高程范围分别是2.58-3.02 m、2.73-3.19 m及3.04-3.59 m,三种植物最适生境高程存在重叠,重叠区域内互花米草具有较高的竞争力。2.长江口典型盐沼植物对盐胁迫的响应及阈值(1)三种盐沼植物的存活率随着盐浓度的增加均呈下降趋势,相同盐浓度处理下互花米草的存活率显著高于海三棱藨草和芦苇的存活率(P<0.05)。(2)盐胁迫在一定程度上抑制了海三棱藨草、互花米草和芦苇的生长及繁殖,随着盐浓度的增加,海三棱藨草及芦苇株高、生物量、分蘖数及结穗率均呈逐渐下降的趋势,而互花米草的株高、地上生物量及地下生物量呈先增加后下降的趋势,均在10 ppt盐浓度时最高。(3)三种典型盐沼植物的耐盐阈值大小依次为:互花米草(43.58 ppt)>海三棱藨草(21.30 ppt)>芦苇(13.35 ppt),即盐浓度分别高于该耐盐阈值时,三种盐沼植物不能有效存活。3.长江口典型盐沼植物对水-盐交互胁迫的响应及阈值(1)随着水-盐交互胁迫的增加,海三棱藨草、互花米草和芦苇的存活率、株高、分蘖数及结穗率均呈逐渐下降的趋势。“盐浓度”、“淹水深度”及“水-盐交互”三种因素对三种盐沼植物生物量积累的抑制作用由高到低为:盐浓度>水-盐交互>淹水深度。(2)海三棱藨草、互花米草和芦苇在淹水深度(x)及盐度(y)交互胁迫下的存活阈值关系式分别为:y=-0.2886x+19.22、y=-0.2539x+43.76及y=-0.1141x+15.925。(3)与单因子胁迫相比,水-盐双因子交互胁迫对三种盐沼植物存活及生长的抑制作用更为明显。互花米草比本地物种海三棱藨草和芦苇对水-盐胁迫具有更强的耐受性。更多还原

【Abstract】 Coastal wetlands are the transition zones of land and ocean ecosystem which are one of the most productive in nature ecosystems.They play an important role in maintaining the ecological balance of habitats and regulating the carbon cycle.As an important part of coastal wetlands,salt marsh species have high primary productivity.It is beneficial to the maintenance of regulating climate,purifying water quality,and maintaining coastline and the structure and function of wetland ecosystems.Flooding and salinity are the main environmental factors of coastal wetlands,affecting the survival,growth and distribution of salt marsh species.However,sea level rise in the future may cause flooding stress and saltwater intrusion,which will cause salt marsh speices to face the high challenge of flooding and salinity interaction stress,which affect the structure and function of the coastal wetland ecosystem.The ecosystem can maintain a stable state by self-regulation when the flooding-salinity stress are small.Once the disturbance exceeds the survival threshold of salt marsh species,it will cause irreversible changes in ecosystem and seriously affect the structure,function,stability and sustainable development of the coastal wetlands.Therefore,the research of effect and threshold of salt marsh species to flooding-salinity stress will provide effective management suggestion before major changes in the system,which also makes sense for ecosystem protection and sustainable management.In this study,three typical salt marsh species(i.e.Scirpus mariqueter,Spartina alterniflora,and Phragmites australis)were investigated in the Yangtze River Estuary.The elevation simulation experiment carried out in Nanhui Dongtan of Shanghai,and the salinity stress and flooding-salinity interaction stress simulation experiment carried out in the greenhouse.Regularly monitor the survival rate,plant height,number of tillers,and ear setting percentage of three typical salt marsh species,and measure the aboveground and underground biomass at the end of the growing season.The model of logistics fitting were used to determine the elevation threshold,the salinity threshold and the interaction threshold of flooding-salinity stress of three typical salt marsh species,which to investigate the effects of elevation,flooding,salinity and flooding-salinity interaction on their survival,growth and reproduction.The results were as follows:1.Respones and thresholds of typical salt marsh species to habitat elevation in Yangtze Estuary.(1)The plant height,the number of tillers and the aboveground biomass of S.mariqueter,S.alterniflora and P.australis increased firstly and then decreased with increasing elevation.The largest number of tillers and the maximum aboveground biomass of three salt marsh species at elevation of 2.80 m,2.96 m and 3.30 m,respectively.(2)The elevation thresholds of three typical salt marsh species in the Yangtze River Estuary were as follows: S.mariqueter(2.36 m)< S.alterniflora(2.51 m)< P.australis(2.79 m).When the elevation were lower than the threshold respectively,the three salt marsh plants died;The daily duration flooding threshold was as follows: S.mariqueter(6.25 h/d)> S.alterniflora(6.00 h/d)> P.australis(5.33 h/d).When the average duration of flooding continued above this threshold,three salt marsh plants died.(3)The optimum habitat zone elevation were 2.58-3.02 m for S.mariqueter,2.73-3.19 m for S.alterniflora and 3.04-3.56 m for P.australis.And S.alterniflora had a stronger competitive in the overlap area.2.Respones and thresholds of typical salt marsh species to salinity stress in Yangtze Estuary.(1)The survival rate of S.mariqueter,S.alterniflora and P.australis appeared a decreasing trend with the increasing salinity,and the survival rate of S.alterniflora under the same salinity was significantly higher than S.mariqueter and P.australis(P<0.05).(2)The growth and breeding of S.mariqueter,S.alterniflora and P.australis were all significantly affected by salinity.The plants height,the biomass,the number of tillers and ear setting percentage of S.mariqueter and P.australis appeared a decreasing trend with the increasing salinity,but them of S.alterniflora showed the first increasing and then decreasing trend,which all were the highest when the salinity was 10 ppt.(3)The salinity threshold of three saltmarshes were as follows: S.alterniflora(43.58 ppt)> S.mariqueter(21.30 ppt)> P.australis(13.35 ppt).When the salt concentration was higher than the salt tolerance threshold,three salt marsh plants died.3.Responses and thresholds of typical salt marsh species to flooding-salinity interaction stress in Yangtze Estuary.(1)The survival rate,the plant height,the number of tillers and the ear setting percentage of S.mariqueter,S.alterniflora and P.australis were all decreased gradually with increasing flooding-salinity interaction stress.The three factors of “salinity”,“flooding depth” and “flooding-salinity interaction” on the biomass accumulation of three salt marsh species from high to low were: salinity > flooding-salinity interaction > flooding depth.(2)The threshold equation of flooding(x)and salinity(y)interaction stress of S.mariqueter,S.alterniflora and P.australiswe were as follows: y =-0.2886 x + 19.22,y =-0.2539 x + 43.76 and y =-0.1141 x + 15.925.(3)Compared with single factor stress,flooding-salinity interaction stress had more significant inhibition on the survival and growth of three salt marsh species.S.alterniflora had stronger tolerance to flooding and salinity interaction stress than S.mariqueter and P.australis.更多还原