【作者】 徐飞；

【导师】 王仁卿；

【作者基本信息】 山东大学 ， 生态学， 2009， 博士

【摘要】 由于全球气候变化的影响已逐渐接近并有可能超出地球系统的正常承载阈值,加之过于频繁的人类活动使森林生态系统遭到了严重破坏,生态功能退化严重。对植物的影响主要是引起植物原先所适应的环境梯度的变化,引起包括空间环境梯度和时间环境梯度的改变,而其中极端气候所导致的干旱胁迫日益严重以及生境破碎化下的光环境异质性加剧成为了近年来植物研究较为关注的问题。植物体通过整株以及叶片的各种性状表现出对于变化环境的适应,各种性状在不同环境下以表型可塑性和异速生长的方式响应诸多压力和约束,进行植物与环境之间相互关系及基本机制的研究成为现代植物生理生态学研究的重要内容。本论文以麻栎和刺槐这两种山东省暖温带常见落叶阔叶共生树种为对象,利用现代生理生态学分析方法和测量手段,研究了两者在不同的水分和光照环境下整株形态生长、生物量积累和分配、叶片的形态、光合特性、生理生化反应、叶运动特性等方面,研究结果将丰富全球环境变化的研究内容,对植物水分生理生态、抗逆生理机制、光合生理生态等领域的研究具有重要意义,将有助于理解共生物种的适应及生态位分化机制、气候变化与植物抗逆性关系,为丰富区域植被-气候关系数据库、指导植被恢复重建、制定区域生态环境可持续发展等方面提供科学数据和理论依据。通过模拟夏季持续干旱及随后的降雨,研究了麻栎和刺槐这两种不同根系统结构物种在不同生境下其光合能力对干旱和降雨的敏感性反应。结果表明,面对夏季持续的干旱,深根系的麻栎受干旱胁迫的影响程度与浅根系的刺槐相比较低。林缘麻栎幼苗的净光合速率、气孔导度、光系统Ⅱ表观量子效率在午间降低较小,傍晚恢复较好,蒸腾速率在全天相对较高;雨后各项光合指标都有所恢复,林缘幼苗由于所经受的胁迫强度大于林下,受胁迫的植物在恢复过程中存在一定程度的后效应,林下刺槐光合各参数日均值的增幅均大于麻栎,麻栎午间仍存在明显的光合午休。说明麻栎作为深根植物耐旱性相对较强,干旱期间光合能力有一定程度的维持,但在雨后恢复较慢;而刺槐作为浅根植物耐旱性相对较差,干旱期间光合受影响较大,但能快速利用降雨进行光合恢复。通过整盆称重法设置4个土壤水分处理,研究麻栎和刺槐幼苗形态结构、光合特性、生物量积累及其分配对水分胁迫的可塑性响应。结果表明,随水分胁迫程度的增强,麻栎和刺槐幼苗的株高、基径、总叶面积、冠面积、叶面积指数和总叶数等形态指标均逐渐降低;净光合速率和蒸腾速率逐渐减少,日变化曲线由单峰型向双峰型转变,光合限制因素由气孔限制为主逐渐转变为非气孔限制为主,光系统的保护机制减弱,光抑制程度加剧,水分利用效率在中度水分胁迫下最高;各器官的生物量积累降低,光合产物向地下部分尤其是侧根迁移,使根冠比增大和叶面积比率减少;叶绿素含量变化差异不明显。水分胁迫改变了形态的异速生长曲线,可塑性指数分析表明幼苗主要通过调节形态和光合能力来适应水分环境的变化,生物量积累和分配的差异可能存在异速生长的影响。麻栎和刺槐由于幼苗生长方式的不同,水分胁迫的影响效果存在差异,麻栎主要是影响光合能力,刺槐主要是影响地上形态和生物量。通过搭建遮阳棚设置3个光照强度,研究麻栎和刺槐幼苗形态结构、光合特性、生物量积累及其分配对不同光照强度的可塑性响应。结果表明,极度弱光环境限制了幼苗的株高、基径、总叶面积、冠面积、叶面积指数和总叶数等形态指标的增加,但适度遮荫有利于幼苗的形态生长,光照对形态的异速生长曲线影响较小,刺槐较麻栎的变化更明显一些;随遮荫程度的增加,麻栎幼苗的净光合速率曲线由双峰型逐渐变为单峰型,刺槐幼苗由于叶运动的保护机制基本维持单峰型,麻栎各光合参数逐渐降低,刺槐则在适度遮荫下最大,光能利用效率均显著增大;随光照强度的减弱,麻栎各器官的生物量积累降低,叶面积比率的增加和根冠比的减少有利于增加光能的捕获,而刺槐的生物量积累和分配则在适度遮荫下达到最优;各叶绿素含量均显著上升,而叶绿素a/b则逐渐下降。麻栎和刺槐显示出不同的生存策略和光利用策略,在一定程度上可以揭示它们在阔叶林群落中不同的演替地位。通过测量叶片角度在不同环境下的变化以及相应的叶绿素荧光参数,研究叶运动的特点及其保护效应。结果表明,麻栎叶片不存在明显的叶片运动,刺槐叶片具有明显的中脉角和叶柄角的变化,两者在不同环境下的变化存在着一种协同互作关系。光照是引起叶片运动的主要因素,低光下叶片下垂,常光下叶片竖起。刺槐中脉角的节律性运动在长期遮荫处理下丧失,但在短期胁迫和恢复期仍然存在,表现出在光—暗转换的滞后与暗—光转换的迅速恢复。不论是在胁迫初期、末期还是恢复初期,干旱环境下的叶片上翘的程度更大。通过叶绿素荧光响应曲线、恢复曲线和叶绿素含量的测量,也可以看出在常光环境下叶片增加了过量光能的耗散能力,低光下则增加光能捕获的能力,干旱条件下叶运动的增强能有效降低叶片光抑制的程度,从而有效的保护光合机构避免光伤害。叶片通过日变化和不同环境下的中脉角的角度差异所体现出来的避光性运动,以及通过不同方位叶片中脉角和叶柄角的角度差异所体现出来的趋光性运动,反映叶片快速的适应性运动与整个冠层长期缓慢的适应性策略协调作用保障了植物的正常生长以及对胁迫更好的适应。通过测量野外和控制实验中幼苗的叶形态指标,研究环境对叶形态的影响程度及规律。结果表明,在野外和模拟试验中,大部分叶形态参数都发生了显著的变化,并且具有较高的一致性。光照是导致叶形态可塑性的主要因素,由干旱引起的形态变化主要归结于异速生长。由于水光供应的缺乏,叶面积、叶干重、叶长和叶宽都变小,协方差分析表明叶长和叶宽仅受叶面积的影响。叶柄在遮荫下并未明显延长,可能是由于存在叶片与叶柄、主脉与侧脉之间在功能组织和支撑结构间的权衡关系。干旱胁迫引起叶子变窄,遮荫胁迫引起叶子变宽,叶长/叶宽未能完全反映出叶形的这种变化,而通过对麻栎叶片三部分的比例(通过叶膨大和最宽部位划分)的测量起到补充效果,叶形的改变在资源获取和保护中寻求平衡。胁迫下叶侧脉密度增加以加强胁迫下的机械支撑和水分供应,叶齿数的增多能通过更活跃的光合活性保证遮荫下幼苗的生存和生长,然而由于齿数增多会导致高蒸腾的原因限制了干旱胁迫下叶齿数。复叶与单叶的叶形态差异主要是由于小叶既是一个独立的单元,又是复叶整体的一部分,小叶叶形态的变化需要同时考虑整个复叶的影响。总之,本研究认为,麻栎和刺槐幼苗在不同的生境条件下通过整株以及叶片性状的表型可塑性和异速生长响应环境的变化,反映了两者通过多方面的适应调节,保证了幼苗在不同生境下的正常生长和生存,并使其能够适应未来较大程度的环境变化,因此也成为了鲁中山区进行植被恢复的理想树种。更多还原

【Abstract】 Because of global climate changes and frequently anthropization by which the effects will reach the threshold of carrying capacity of the earth system,forest ecosystems suffer from severe destroy going with serious degradation of ecological functions.The main effects on plants are causing the changes of environmental gradients to which the plants are used to adapt.It includes the changes of spatial or temporal environmental gradients.In recent years,more and more researches are focused on the severe drought caused by extreme climate events and light heterogeneity in habitat fragmentation.The traits of whole plant and organisms respond to environmental variation on various timescales.Phenotypic plasticity enables a given genotype to produce a range of trait values across environmental gradients and within the lifetime of an individual organism.By contrast,variation in selection pressures along environmental gradients gives rise to heritable differences between populations or species,through the intergenerational process of evolution. There is often strong similarity between the plastic and allometry responses of quantitative traits to environmental gradients.It has became a hot point in modern plant ecophysiological researches.In this study,we chose Quercus acutissima Carr. and Robinia pseudoacacia L.as the research objects.The two plant species are normal deciduous broadleaf species and usually form the mixed forests in north China.We used modern ecophysiological equipments and measurements to study whole plant growth,architectures,biomass accumulation and allocation,leaf morphology,leaf movements,photosynthesis,biophysiology and biochemistry in the seedlings of these two species under different light and water conditions.The results will enrich the research contents of global climate changes,plant hydro,stress and photosynthetic ecophysiology,help to understand the mechanisms of adaptation and niche differentiation of coexisting species,and correlate the relationships between climate and plant tolerance.It may also provide evidences for building the database of vegetation and climate,supervising the reforestation and establishing the blueprints for local ecological environment and sustainable development. Different responses of deep and shallow root system of Q.acutissima and R. pseudoacacia to a precipitation pulse event after a prolong drought period in summer was studied to analyze the photosynthetic sensitivity of these two species.The results indicated that the deep root system species could tolerate more serious drought stress than the shallow root system one when facing to the summer drought. When compared with R.pseudoacacia in the simulated forest edge,the photosynthetic rate,stomatal conductance and effective quantum yield of PSII became less depressed for Q.acutissima in the simulated forest edge.Besides the lower degree of noon inhibition,these parameters could recover to a better extent in the evening.And the transpiration rate maintained higher values during the whole day.All parameters had a certain recovery after the precipitation,and the degrees of recovery were time lag for the seedlings in the simulated forest edge because of the higher press levels.The increased extents of photosynthesis were larger for R. pseudoacacia in the simulated understory.Midday depressions of photosynthesis were still obvious for Q.acutissima.The deep root system species have a higher drought tolerance.They can maintain the photosynthesis during the drought periods but can recover slowly after the rainfall.The shallow root system species are just diametrically opposite.A water gradient experiment with four different water supply levels was conducted by artificial water control in the rainout shelters to study the plasticity of morphological architecture,photosynthetic characters,biomass accumulation and allocation in Q.acutissima and R.pseudoacacia seedlings in response to diverse water stress.The results showed that morphological variables of height,stem diameter,total leaf area,crown area,leaf area index and total leaf number decreased with increased in water stress.Consistent with the increasing leaf water saturation deficit in water stress,net photosynthetic rate and transpiration rate also decreased. The diurnal course changed from single-peak to two-peaks patterns.Factors that limited photosynthesis shifted from stomatal limitation to non-stomatal limitation. Reduced light use efficiency,as well as weak photoprotective effect in photosystem, caused more serious photoinhibition.Water use efficiency can be improved under moderate water stress.Biomass accumulations to each organ were restricted by the deficit of soil water content.Under water stress,more photosynthetic products were transferred to belowground biomass,especially to the lateral roots.As a result, carbon allocation patterns were altered by increased in root mass ratio at the expense of decreased leaf mass ratio,and it therefore led to higher root to shoot ratio,lower leaf area ratio and lower specific leaf area.The contents of chlorophyll were not significantly different under water stress.Allometric trajectories of morphology were changes in different water treatments.Plasticity index analysis indicated that the seedlings could adapt to diverse water stress through plastic responses in morphology and photosynthesis,whereas the differences of biomass accumulation and allocation might be partly affected by the allometry.The effects of water stress on seedlings of Q.acutissima and R.pseudoacacia showed some differences for the different grow patterns.The former was sensitive in photosynthesis,but the latter was affected in morphology and biomass of aboveground.A light control treatment with three light gradients was conducted in shade shelters covered by plastic films or woven black nylon nets to study the plasticity of morphological architecture,photosynthetic characters,biomass accumulation and allocation in Q.acutissima and R.pseudoacacia seedlings in response to diverse gradients of light.The results showed that morphological variables of height,stem diameter,total leaf area,crown area,leaf area index and total leaf number were totally inhibited under serious shade conditions.Whilst,growth of seedlings had some advantages under moderate shade treatments.Effects of light on allometric trajectories of morphology were smaller in compared with the water effects,and the changes in R.pseudoacacia were more obvious than Q.acutissima.The diurnal course of photosynthetic rate changed from two-peaks to single-peak patterns in Q. acutissima with the light decreasing,and photosynthetic parameters and biomass accumulation were also decreased.But R.pseudoacacia could maintain the curves for its leaf movement,and the maximum of photosynthetic parameters and biomass accumulation occurred under moderate shade treatments.Higher leaf area index and lower root to shoot ratio could increase the capacity of light capture.Meanwhile,the contents of chlorophyll were increased and Chl a/b were decreased.The different strategies of light utilization can reveal the status of tree species in succession to a certain extent.Leaf inclination,physiological and biochemical parameters of Q.acutissima and R.pseudoacacia seedlings were studied under different stress conditions to find out the features of leaf movement and its protective functions.The results showed there was no significant leaf movement in Q.acutissima.Co-operation of midrib and petiole angles caused significant leaflet movement in R.pseudoacacia under different water and light conditions.Leaf inclination was affected mainly by light;a low level of irradiance caused leaves to be arranged horizontally.Diurnal rhythmicity was lost after the long-term stress,but resumed,in part,in the recovery period.It reflected the hysteresis in the light-dark transformation and rapid recovery in the dark-light transformation.Drought stress caused leaves to tilt more obviously during the whole periods and decreased damage to the photosystem.It could be reflected by changes of chlorophyll fluorescence and chlorophyll content.Significant physiological changes occurred under different conditions of light.Increased energy dissipation and light capture were the main responses to high and low level of irradiance,respectively.Sun tracking movement in a single leaf and sun avoiding movement in the whole plant coexisted,which reflected the rapid leaf protective movements and the tardive adaptation in the whole canopy harmoniously guaranteed that the seedlings could show better response to the stress and normally growth.Habitat effects on leaf morphology and the underlying regulations were studied by a field measurement and simulated experiments with interactive treatments and different gradients of water and light availability.The morphological parameters we investigated include leaf size,shape and venation pattern which can be easily measured in the field.The results indicated that leaf morphology variations occurred over most of the parameters,and the causes were consistent between the field study and lab experiments.Light was the main factor inducing leaf morphological plasticity.The variations caused by drought were due mainly to the allometry.The leaf size,including leaf area,leaf mass,leaf length and width,became smaller with a short supply of resources.Leaf length and width were only affected by leaf area using analysis of covariance.The leaf petiole did not lengthen under shade stress, suggesting a trade-off relationship between functional tissues and support structures in leaf lamina and leaf petiole.Meanwhile,trade-offs between investments in support and functional structures also optimized the venation pattern of major and minor veins.Leaf shape became narrower in drought and broader in the shade,as reflected in changes in leaf elongation and three leaf fractions of Q.acutissima in supplement.Leaf elongation and fractions of the lamina area altered to enhance resources acquisition and conservation.Higher vein density played a part in enhancement of mechanical support and water supply under stress conditions. Leaves with more teeth show more active photosynthesis for better survival and growth,but are disadvantageous in xeric environments because of higher transpiration.Leaflets of R.pseudoacacia partially played a role such as leaf teeth, for they are not only individual units,but also a part of the compound leaf.The variations of leaflet morphology should consider the benefits of whole compound leaf.In conclusion,this research shows that the seedlings of Q.acutissima and R. pseudoacacia under different habitats can respond and adapt to environmental changes via phenotypic plasticity and allometry of whole plant and leaf traits.It reflects that there are many adaptive mechanisms,by which these two species assure their seedlings can normally grow and survive under different habitats,and may adapt to more fluctuant climate changes in the future.All of these may be important reasons for Q.acutissima and R.pseudoacacia to be the ideal species for ecological reconstruction in the center of Shandong mountain areas.更多还原