【作者】 艾丽皎；

【导师】 张银龙；

【作者基本信息】 南京林业大学 ， 生态学， 2013， 博士

【摘要】 三峡库区消落带自然环境复杂多变，冬蓄夏汛水文生态过程形成典型的淹水-落干的干湿交替环境已引起国内外环境生态研究者的广泛关注。目前，在三峡地区资源与环境友好型利用背景下，消落带植被恢复与重建成为库区消落带生态环境治理的重要内容，但如何评价先锋适生植物的标准还存在较大分歧，特别是先锋植物对干湿交替生境的生理生态响应机制更是知之甚少。本研究以消落带植物南川柳（Salix rosthornii）作为研究对象，研究消落带自然环境条件下植被恢复示范区南川柳生态位特征、植物群落以及抗性生理指标响应机制，揭示南川柳在自然生境下植物群落及抗性生理指标的变化规律；在室内条件下，借助盆栽模拟实验，模拟干旱和水淹胁迫条件，分析南川柳抗性生理指标和光合作用特征适应机制，探讨南川柳对干旱、水淹胁迫的生理生态响应及光合作用特征的适应机制，为三峡库区消落带植被恢复与重建工作中适生植物的筛选提供理论依据。通过野外样方调查，研究了重庆主城石门段消落带植被恢复示范区主要优势种植物优势度、生态位特征。结果表明，石门消落带示范区主要优势植物种南川柳、秋华柳、中华蚊母、卡开芦、野青茅、甜根子草、扁穗牛鞭草、水苦荬的生态位宽度分别在乔、灌、草本层中占有优势地位；各层次生态位重叠表现为草本层＞乔木层＞灌木层，表明该示范区内植物生态位重叠度较大，分化不明显，种间竞争激烈。通过南川柳与其它39种主要植物种的生态位宽度及生态位重叠值分析比较，表明南川柳在乔木层占据绝对优势，具有较强的耐淹水能力，在消落带不同高程带均可以种植，能与其他灌木及草本植物形成优势群落。根据三峡库区重庆主城段消落带冬蓄夏汛的水文生态过程，研究了典型的冬季蓄淹水没和夏季汛期淹水对消落带不同高程土著种植物南川柳的盖度、基径和株高等生物学特征及其物种多样性格局的影响。结果表明：冬季水淹胁迫显著增大了172m高程南川柳平均盖度与株高和175m平均株高（P＜0.05），而对于两高程基径影响均未达到显著水平（P＞0.05）。夏季水淹胁迫后，172m高程南川柳平均盖度显著降低（P＜0.05），而对于基径和株高影响较小（P＞0.05）；175m高程南川柳生物学特征变化均未达到显著水平（P＞0.05）。经过冬季和夏季淹水，172m高程物种Patrick丰富度指数和Shannon-Wiener多样性指数先增大后降低，而175m则出现相反变化趋势；172m高程Simpson优势度指数显著增大（P＜0.05），而175m仅冬季淹水后显著增大（P＜0.05）。就淹水后生物特征短时效而言，南川柳可以有效地作为三峡消落带植被恢复的适生物种，为降低夏季淹水后由泥沙堆压造成的物理胁迫，需要适当的人为管护。在野外原位条件下，研究了夏季汛期水淹过程（淹水时长、淹水频率和淹水深度）对不同高程带南川柳抗性生理指标的影响。在2012年夏季汛期观测到了具有明显特征的干湿交替过程总共有两次，初次淹水时长持续35天，第二次则只持续了5天。研究结果表明，172m南川柳RWC和EL值经历初次水淹后迅速增大而后降低，而175m和对照组分则出现逐渐降低的趋势；172m和175m高程带南川柳MDA含量先增大后降低，对照组分则是逐渐升高；南川柳脯氨酸含量的变化趋势也大致呈先增大后降低的变化规律，172m高程是逐渐增大的；南川柳抗氧化酶活性变化趋势不是同步统一的，这可能与各种抗氧化酶的作用机制、植物体的反馈调节及消落带高温伏旱条件密切相关。总体而言，夏季汛期水淹对低高程消落带植物南川柳的逆境胁迫作用较为明显，对于中上部的影响不是很显著。此外，库区夏季的高温伏旱胁迫对于消落带上部南川柳的胁迫作用较为显著，这也表明消落带植物南川柳的生理响应是由消落带夏季汛期干湿交替胁迫和高温伏旱胁迫共同作用的结果。为了探明消落带植物南川柳的耐旱特性，在盆栽条件下，对南川柳1年生幼苗采用控水方式进行干旱胁迫处理，同时设置对照组进行正常灌溉，测定叶片相对含水量(RWC)、电解质渗漏(EL)、丙二醛(MDA)等一系列与植物耐旱能力相关的生理指标以及抗氧化性酶活性的变化。结果表明：在干旱胁迫下南川柳幼苗叶片具有较强的水分保持能力，并且在复水后有相对较快的恢复能力；10天和20天的干旱胁迫对南川柳叶片电解质渗漏的影响与对照相比差异不显著，随胁迫时间的持续，EL和MDA都显著升高（P＜0.05）。在干旱胁迫下，实验组分南川柳叶片脯氨酸含量大致呈递增趋势，并且在干旱处理40天达到最大值，表明南川柳对于干旱胁迫的适应能力约为40天。南川柳幼苗叶片超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性整体呈先升高后降低的趋势，其中CAT对胁迫最为敏感，而POD响应相对较为缓慢；在复水20天后3种酶活性有所恢复，但均未恢复到对照的水平。模拟研究了三峡库区消落带水分变化特征对南川柳幼苗光合作用特征的影响，干旱处理对于南川柳净光合速率具有抑制作用，形成显著的的负响应能力，但由于逆境胁迫干扰强度的差异，净光合速率并不能很好地表达各处理组分之间光能合成响应能力的大小。南川柳幼苗净光合速率受到多种因素的综合影响，对不同干旱胁迫处理表现出来的净光合响应能力，与其光合气体交换参数和资源利用效率密切相关，发现南川柳净光合速率与蒸腾速率、表观CO2利用效率和叶片相对含水量呈现显著正相关（P＜0.05）；与气孔导度显著相关（P＜0.05）；与胞间CO2浓度呈显著负相关（P＜0.05），与水分利用效率并无显著相关性（P＞0.05）。通过室内模拟水淹胁迫实验，结果表明，只有淹水持续时间达到一定阈值时，不同水淹深度对于南川柳叶片含水率才能产生显著影响。南川柳EL对于水淹深度70cm较为敏感，对于40cm较为适应。在水淹胁迫下，南川柳耐水淹的极大值为持续淹水30天。南川柳MDA含量对于水淹时间具有较广的生态幅，水淹深度越大，MDA含量越高。在水淹持续时间20天内，南川柳脯氨酸含量较高。从南川柳叶片抗氧化酶活性来看，淹水30天并未是南川柳最大的耐淹水时长，当淹水深度较大时，植株才会通过抗氧化酶系统来进行生理生化调节，以适应水淹胁迫对植株造成的伤害。更多还原

【Abstract】 The natural environmental characteristics of Three Gorges Reservoir are changing andcomplex. The alternate flooding and drying environment induced by the typical hydro-ecologicalprocesses of winter impoundment and summer flooding，the widespread concern has been causedamong the environmental and ecological researchers. At present, the water-level-fluctuating zone(WLFZ) vegetation restoration and reconstruction becomes one of the major tasks of the ThreeGorges Reservoir ecological environmental management under the context of resources andenvironment eco-friendly utilized. However, large differences concerning about criterions exist inhow to evaluate pioneer suitable plants. Furthermore, little is known about the physiological andecological responses of the pioneer plants to the alternating wet and dry habitats. In this study,fluctuating zone plants Salix rosthornii was selected as the researched object. A field plotinvestigation was conducted to determine its plant communities, niche characteristics andresponse mechanism of the physiological resistance in natural habitats. Parallel pot experimentswere carried out under laboratory conditions, which simulated drought and flooding stressconditions, in order to analyze physiological characteristics of resistance and photosyntheticcharacteristics of Salix rosthornii. This research tries to provide a theoretical basis for suitableplant selection in the reservoir restoration and reconstruction, particularly for indigenous plantspecies applied in ecological environment fluctuating zone.By a field quadrat survey, dominances of the dominant species, niche characteristics wereinvestigated of Shimen fluctuating zone vegetation restoration demonstration area of main cityChongqing. The results indicated that:1) The dominant plants in Shimen fluctuating zonedemonstration area were: Salix rosthornii, Salix variegate, Distylium chinense, Saccharumspontaneum, Phragmites karka, Deyeuxia Arundinacea, Hemarthria compressa, Veronicaundulate. And their niche breadth occupies a dominant position in tree, shrub, and herb layer,respectively;2) Various levels niche overlap performance was herb layer> tree layer> shrub layer,indicating that plant niche overlap in the region, the differentiation is not obvious, and theinterspecific competition is fierce. The niche breadth and niche overlap of Salix rosthornii werecompared to other39main plant species in the demonstration area, which indicated that Salixrosthornii had absolute dominance in the tree layer. This survey proved that Salix rosthornii had astrong resistance to flooding; it could be used at different elevations of the fluctuating zone andform dominant community with other shrubs and herbaceous plants.Based on the hydrological process of Three Gorges Reservoir, plant coverage, basal diameter and plant height of Salix rosthornii at different elevations were measured. The effects of seasonalflooding on biological characteristics and species diversity were also analyzed. The resultsshowed that: winter flooding significantly increases the average coverage and plant height at172m altitude and the average plant height at175m altitude (P <0.05). However, plant basaldiameter had no difference at either elevation (P>0.05). After summer flooding, the averagecoverage reduced significantly at172m altitude (P <0.05), while the basal diameter and plantheight were less affected (P>0.05); At175m altitude, none of the biological characteristicsreached significance level (P>0.05). After the winter and summer flooding, the172m elevationspecies Patrick richness index and Shannon-Wiener diversity index first increases and thendecreases, while the175m showed the opposite trends; At172m elevation, the Simpsondominance index significantly increased (P <0.05), while at175m it only increased after winterflooding (P <0.05). For the short time biological characteristics after flooding, Salix rosthorniican be effectively used as the Three Gorges fluctuating zone vegetation restoration species. Inorder to reduce the physical stress caused by sediment pile pressure after summer flooding, itrequires proper maintenance and protection.In field conditions, the effects of summer flooding on physiological responses of Salixrosthornii were investigated. The flooding duration, flooding frequency and depth of flooding atdifferent elevation were measured. Two typical alternating wet and dry processes were observedin the2012summer flood season. The initial flooding lasted35days, and the second processlasted only5days. The results showed that, RWC and EL of Salix rosthornii at172m altitudeincreaseed rapidly after the initial flooding and then decreased, while the175m and the controlgroup showed a decrease trend. The MDA content of treatment group increased and thendecreased at both172m and175m elevation, while the control gradually increased. The prolinecontent had the same trends as the MDA. The activities of three antioxidant enzymes trends werenot synchronized, which might due to the variety of antioxidant enzymes, plant feedbackregulation mechanism, and the high temperature and drought conditions of the fluctuating zone.Overall, the summer flooding had a significant impact on Salix rosthornii at lower elevation, butnot so obvious at middle or upper part of the fluctuating zone. In addition, the reservoir area hightemperature and drought stress in summer flooding season also had great influences on the plantsat upper elevation, which suggests that physiological responses of Salix rosthornii were thecombine effects of the alternating wet and dry conditions and high temperature and droughtstress.In order to ascertain the drought tolerant characteristics of fluctuating zone plants Salixrosthornii, and provide theoretical basis for fluctuating zone population structure and plantselection, a pot experiment was conducted on Salix rosthornii1-year-old seedlings under watercontrol drought stress. Leaf relative water content (RWC), electrolyte leakage (EL),malondialdehyde (MDA) and a series of physiological indicators related to plant droughttolerance and resistance to oxidation activity changes were measured. The results indicated that:1) Salix rosthornii seedling leaves had strong moisture retention capacity under drought stress and relatively fast recovery after re-watering;2)10days and20days of drought stress had nosignificant effects on EL and MDA. With the continued drought stress, EL and MDA increasedsignificantly;3) the overall trend of superoxide dismutase (SOD), peroxidase (POD) and catalase(CAT) activity under drought stress was first increased and then decreased. CAT was the mostsensitive to drought stress, while POD was relatively insensitive. After re-watering20days, allthree enzyme activities started to recovery, but not to the level of the control group. Thesimulated study also investigated the impact of the Three Gorges Reservoir water changecharacteristics on the Salix rosthornii seedlings photosynthesis characteristics. The resultsshowed that drought stress had a significant negative effect on net photosynthetic rate. Due to thedifferences of stress disturbance intensity, however, net photosynthetic rate might not be the bestindicator to depict the size of the light synthetic response capacity among treatments. Variousfactors could affect net photosynthetic rate. The photosynthetic gas exchange parameters and theefficiency of energy use are closely related to the net photosynthetic response capabilities underdifferent drought stress. This study found that net photosynthetic rate was positively related totranspiration rate, CO2utilization efficiency and relative leaf water content (P <0.05). It wassignificantly related to stomatal conductance (P <0.05); however, intercellular CO2concentrationwas negatively related (P <0.05), and was not significantly related to water use efficiency (P>0.05).A30-day indoor simulated waterlogging experiment was conducted to investigatewaterlogging resistance of Salix rosthornii. The results showed that different waterlogging depthhad an impact on the relative leaf water content when waterlogging duration reaches a certainthreshold. The leaf electrolyte leakage (EL) was more sensitive to70cm waterlogging than40cm.During the waterlogging cycle, the highest EL was the30-days. The MDA content underwaterlogging had wide ecological amplitude, the greater the depth of waterlogging, the higher thecontent of MDA. In20days of duration, proline content was higher under waterlogging than thecontrol. Leaf antioxidant enzyme activities did not reach to its peak value during the experiment,and this study found that physiological and biochemical regulation through antioxidant enzymesystem to accommodate waterlogging stress only take effects when waterlogging depth wasrelatively higher.更多还原