【作者】 杜宁；

【导师】 王仁卿；

【作者基本信息】 山东大学 ， 生态学， 2010， 博士

【摘要】 全球气候变化导致世界范围内的干旱日益严重,再加上自然和人为因素造成的环境因子的异质性和扰动,森林植被面临着越来越严重的生存压力,植物与环境尤其是变化的环境的关系问题再一次成为生态学家关注的焦点。植物体通过根、茎、叶等各个组成部分的相互协调适应不同的环境,利用现代化的实验控制手段和仪器分析手段研究植物对环境生理生态方面的适应机制成为进几十年来全球变化生态学的重要研究方向。本论文以暖温带常见的灌木荆条(Vitex negundo var. heterophylla)为主要研究对象,从它本身的生长特性以及对水分、光照等环境因子的响应机制方面解释了其成为暖温带广布优势种的原因,并将荆条与暖温带其它常见灌木酸枣(Ziziphus jujuba var. spinosa)、扁担木(Grewia biloba var. parviflora)、紫穗槐(Amorpha fruticosa)和火炬树(Rhus typhina)进行了叶性状及生物量分配的比较研究,分析了几个物种生理生态学方面的差异,实验共分为五部分：前三部分研究了荆条对于水分和光照的生理生态响应以及野外荆条叶片性状的时空变化,后两部分比较了荆条与其它灌木,尤其是酸枣的生理生态特性的差异。本论文的研究结果将有助于理解灌木层共生物种的适应及生态位分化机制、随着演替的进行和未来的气候变化,物种组成可能的变化趋势,并为植被重建、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。利用大棚内的控制实验,研究了荆条幼苗对于不同土壤水分含量的生理、形态方面的适应。研究结果表明：随着水分胁迫的加深,荆条幼苗的叶片净光合速率、蒸腾速率、气孔导度、最大量子产量等生理指标逐渐下降,但是光合速率和蒸腾速率下降的程度并不一致,轻度水分胁迫下气孔因素对净光合速率的下降起主要作用,重度水分胁迫下非气孔因素起主要作用。荆条幼苗的生长高度、基径、冠幅、生物量产量均随着水分的减少而下降,轻度和中度水分胁迫并没有影响到荆条的相对生长速率,并且在轻度和中度水分胁迫下,生物量更多的分配于根中增强对水分的吸收能力。在重度水分胁迫下,荆条幼苗的生长几乎停滞,新陈代谢受到影响,幼苗出现了萎蔫现象,小苗不得不将同化物更多的投资于叶片进行光合生产。总之,保证荆条成活和良好生长的关键是幼苗期的水分供应和管护。利用遮阳棚和遮阳网,研究了荆条幼苗对于不同光照强度的适应机制,以及荆条幼苗对于林窗形成、人工伐林等因素带来的变化的光环境的适应。研究结果表明：荆条幼苗对于不同的光照条件具有良好的适应,低光下提高光吸收效率,高光下避免光抑制。低光下的荆条叶片具有低的比叶重(LMA)、高的单位质量叶绿素(Chl)含量、低的叶绿素a、b比值,个体水平上更多的地上生物量分配,这可以保证其对光能的充分吸收利用。高光下的荆条叶片具有良好的热耗散能力,避免过量光量子对叶片的伤害。光照转换(光照增强)之后,荆条的老叶和新叶共同适应新的环境,老叶的生理指标恢复的比较完全,而比叶重只有部分的恢复,对于新叶来说,叶片的含水量升高,叶绿素含量明显升高,特别是低光-高光处理下的新生叶的最大量子产量提高,非光化学淬灭下降,说明叶片的健康度提高,这有可能是低光-高光刚处理时老叶会有严重的光抑制,新生叶的这种生理功能的提高是为了植株在个体水平上的适应。也正是由于在刚转换时存在着严重的光抑制,造成了低光-高光处理下生物量提高的并不是最多。在野外选取了荆条典型的5个生长环境：林外、阔叶林林缘、阔叶林林下、针叶林林窗和针叶林林下,在不同的生长月份取样分析,研究了荆条叶性状不同时间和空间的变化趋势。研究结果表明：在荆条叶片的主要生长期内,叶性状具有明显的时间和空间的变化,不同的取样地点,叶性状具有相似的时间变化规律。叶性状的空间变化主要是由于光照因素造成的,遮荫下的植株采取叶片尺度(低比叶面积)和细胞尺度(高Ch1/N和低Ch1 a/b)上的可塑性提高了光捕获的能力。叶性状的时间变化主要是由于与气候条件相关的土壤环境因子造成的,因此,当我们将采自不同时间(月份)的叶片放在一起分析的时候,要特别注意采样时间的差异对结果的影响。除了环境因子的影响,随着荆条的个体发育,叶性状也会发生一些变化：比叶面积随着叶片生长而减小,说明由于富含碳的化合物的聚集和细胞壁的木质化而造成的叶片密度的增加；6月份叶片中的氮素更多的分配于叶绿素中,说明叶片的营养生长和生殖生长之间存在着氮分配的权衡。利用形态学的测量手段,研究了荆条和酸枣对于水分和光照交叉作用的响应,研究表明：遮荫和干旱对于荆条幼苗形态的影响是正交的,对于酸枣幼苗形态的影响并不一定是正交的,还需要进一步的实验验证。酸枣和荆条具有不同的光能捕获策略,酸枣具有发达的分枝而荆条的分枝很少,取而代之的是长的复叶柄,这对于降低荆条叶片的自遮荫非常重要。对于遮荫的环境,两个物种具有不同的叶片水平和个体水平上的适应策略,而对于干旱的环境,两个物种的叶片可塑性都比较低,主要采用叶间距减小和根冠比增加的方式来提高水分吸收及运输效率。短的叶柄和蜡质的叶片是酸枣提高干旱耐受性的重要性状。不同的形态学特性和对光照和水分不同的响应赋予了这两个物种不同的生态学特性,荆条的耐荫性更强一些而酸枣的耐旱性更强一些,这对于两者在暖温带落叶阔叶林中的共存至关重要。在大棚中盆栽了荆条、酸枣、扁担木、紫穗槐和火炬树五种暖温带常见灌木,比较了它们生理生态方面的差异。研究发现：荆条、酸枣、扁担木、紫穗槐、火炬树在相同的生长环境下体现出了不同的生理生态特性。从叶片生理的角度看,外来物种火炬树和紫穗槐表现出很好的光合优越性,并且对于瞬时变化的光强具有很强的适应能力,这对于两者较好的利用光斑环境将非常有利,而荆条和酸枣对资源的利用比较保守,充分的利用正午的光照是荆条叶片生理的一大优势,扁担木的叶片有较强的气体交换能力,但是通过荧光分析,电子传递的最大值比较低而且正午过后荧光日变化的实际量子产量恢复值也比较慢,其叶片已经体现出来一些荫生性。叶片的结构性状与生理性状往往具有良好的对应关系。扁担木叶片的比叶重,叶绿素a、b的比值都最小,印证了扁担木叶片的荫生性。紫穗槐的支撑结构分配比例最高,这样更有利于支撑其运动的叶片。紫穗槐和火炬树高的光合能力和良好的耐旱能力是两个外来种能够定居下来的重要原因。良好的种子扩散能力、保守的光能利用策略、较强的干扰后恢复能力使得荆条成为暖温带地区的广布优势种。总之,荆条从叶片尺度到整株尺度、从营养生长到生殖生长的生理生态特性以及对于水分和光照良好的适应机制,使其成为暖温带灌木层的广布优势种。荆条叶性状在不同时间和空间的变化同样体现了其对环境因子的良好适应和调节能力。荆条和酸枣这两种具有不同叶片类型的物种,对于水分和光照的响应差异造成了两者生态位的分化。荆条、酸枣、紫穗槐、火炬树和扁担木具有不同的生理生态特性,这对于植被恢复中物种的选择和灌木层物种的分布、演替具有重要意义。更多还原

【Abstract】 Drought is becoming more serious as global climate change in the world, coupled with light environmental heterogeneity and disturbance because of natural and man-made factor, forest ecosystems is suffering growing pressure to survive. The relationship of plants and environment, especially the changing environment, is foucused by ecologists once again. Plants adapt different environment according to the harmonization of root, stem and leaf. With the modern controlled experimental method and instrument analysis method to study the ecophysiological adaption mechanism to environment, is the important research aspect of global changing ecology. In this study, we chose Vitex negundo var. heterophylla as the main research objects. The species is the widely distributed in the shrub layer of north China. We explained why this species is so dominative of shrub layer in warm temperate zone from the growth characteristics and the response mechanism to water and light. We compared the leaf traits and biomass partitioning of Vitex negundo var. heterophylla, Ziziphus jujuba var. spinosa, Grewia biloba var. parviflora, Amorpha fruticosa, and Rhus typhina. There was difference among the five shrub species from the ecophysiological aspect. The results will help to understand the mechanisms of adaptation and niche differentiation of coexisting species and the likely species variation trend with the succession and climate change in the future. It may also provide evidences for vegetation restoration and establishing the blueprints for local ecological environment and sustainable development.A potted experiment was carried out in the greenhouse to study the physiological and morphological adaptation of Vitex negundo var. heterophylla seedlings to different soil water content. With the aggravation of drought, net photosynthetic rate, transpiration rate, stomatal conductance and maximum quantum yield of PS2 became smaller, but the degressive degree was not consistent between photosynthetic rate and transpiration rate, stomatal closure was the dominant limitation at mild to moderate drought, while metabolic impairment became dominant at severe drought. Plant growth was inhibited under water stress, and consequently, all parts of the biomass decreased markedly with drought, but the relative growth rate was not affected under mild and moderate drought. Seedling growth was nearly stagnant, metabolism was affected, seedlings were withered and more was invested in leaf to photosynthesis at severe water stress. Water supply above 15% Field Capacity is recommended for the seedlings for vegetation restoration.Vitex negundo var. heterophylla seedlings were subjected to different light conditions which were carried out with woven black nylon nets. The adaption to the irradiance variation was also investigated to simulate gap formation. There was good adjustment to different light conditions:light absorbed efficiency was improved under low light while photoinhibition was avoided under high light. The lower LMA, higher chlorophyll content, lower chlorophyll a/b and lower root to shoot ratio were all the strategys to ensure the light absorbing adequately. It showed excellent heat dissipation ability in high irradiance, which was used to avoide damage to the leaf. After gap formation, the old leaves and new leaves adapted the new environment together. Fot old leaves, the physiological index recovered completely, while LMA only recovered partially. For new leaves, leaf water content became higher, LMA became lower, chlorophyll content became higher, and there were higher maximum quantum yield and lower non-photochemical quenching in low light (LL)-high light (HL) treatment, which means that the leaves were healthier. There will be heavy photoinhibition after transformation from low light to high light, so the elevation of physiological activity is the adaption at individual level. The biomass increase was not the most which was also caused by the heavy photoinhibition in LL-HL treatment. The elevation of physiological activity and the steady investment to leaves were very important to adapt new environment.Five typical habitats of V. negundo var. heterophylla were selected on the hill, i.e. open forest, edge of deciduous broadleaved forest, understory of deciduous broadleaved forest, gap of evergreen coniferous forest, and understory of evergreen coniferous forest. Leaf traits were analysed from different months. Temporal and spatial variation of leaf traits of the shrub were studied in the regional scale. We found that all the leaf traits, including specific leaf area (SLA), leaf nitrogen (N) and phosphorus (P) content, chlorophyll (Ch1) content, and chlorophyll fluorescence, showed both temporal and spatial variation. The seasonal variation was consistent in different habitats. Light condition was the determinative factor in spatial difference. Plants under shade developed light-capturing behavior at leaf level (lower SLA) and cellular level (higher Ch1/N ratio and lower Ch1 a/b). Soil condition related to climate was the determinative factor in temporal difference. We should pay more attention to analysis when collecting leaves from different months, in order to prevent inaccurate conclusions appearing. Ontogenetic impact to leaf traits also existed over the entire growth season, such as the smaller SLA with growth and higher Chl/N in June. The smaller SLA with age could ascribe to an overall increase in leaf density, which is also associated with accumulation of carbon-rich chemicals and the enhanced lignification of cell walls. The distinct N-allocation pattern enables higher maximum photosynthetic nitrogen-use efficiency in flcwer-leaves to compensate the N allocation to flowers.The combined impact of drought and shade on Vitex negundo var. heterophylla and Ziziphus jujuba var. spinosa, in terms of morphological plasticity, was studied. The interaction of light and water was orthogonal in V. negundo var. heterophylla, but it remained inconclusive in Z. jujuba var. spinosa. Effects of drought and shade on biomass allocation were orthogonal, while effects on biomass production were not orthogonal in Z. jujuba var. spirosa. V. negundo var. heterophylla captured irradiance efficiently with relatively long common petiole and petiolule, while Z. jujuba var. spinosa maintained higher branches to absorb light. Under deep shade, V. negundo var. heterophylla showed larger specific leaf area (SLA), lower ratio of leaf length to width and higher leaf dry mass ratio; while Z. jujuba var. spinosa showed larger SLA and ratio of leaf length to petiole length. In both species, the branch number became smaller, mean leaf space of stem was lower, and root dry mass ratio was higher under drought, but leaf morphology showed little variance to water deficit. The short petiole and waxen leaves are the important characters to enhance drought tolerance in Z. jujuba var. spinosa. Different morphological characters and different responses to light and water endowed the two species with different ecological characteristics. V. negundo var. heterophylla appears to be more shade-tolerant, while Z. jujuba var. spinosa is more drought-tolerant. The species-specific adaptation of drought and shade may be an important mechanism driving forest community dynamics in temperate forests.In order to compare the ecophysiological difference among the five common shrubs in the warm temperate zone, potted seedlings of Vitex negundo var. heterophylla, Ziziphus jujuba var. spinosa, Grewia biloba var. parviflora, Amorpha fruticosa, and Rhus typhina were cultured in the greenhouse. We found that the five species showed different ecophysiological characters. From the leaf physiological aspect, Amorpha fruticosa and Rhus typhina showed a photosynthetic superiority and strong ability to adapt variable irradiance, which is benefit to use the sunfleck. Vitex negundo var. heterophylla and Ziziphus jujuba var. spinosa had conservative resource use strategy; it is the advantage to use irradiance at noon for the former species. The gas exchange ability was higher in Grewia biloba var. parviflora, but the leaves showed somewhat shade-grown character. According to fluorescence analysis, the maximal electron transport rate is the lowest and the recovery of effective quantum yield is the slowest. There is always corresponding relation between leaf structural traits and leaf physiological trais. Grewia biloba var. parviflora showed the lowest LMA and chlorophyll a/b, which verified the shade grown character. Amorpha fruticosa showed the highest supporting structure ratio, corresponding to the moveable leaves. The higher photosynthetic ability and well drought tolerance are the important reasons that the two alien species could settle down. There is no risk of Amorpha fruticosa to the native ecosystem while Rhus typhina showed the strong invasive ability. We should pay more attention when we introduce the alien species to the native ecosystem. Vitex negundo var. heterophylla is the widely distributed shrub species in the warm temperate zone because of the well diffusivity, conservative resource use strategy, and good recovery ability after disturbance.In conclusion, the ecophysiological characters from leaf scale to whole plant scale and well adaption mechanism to light and water enable Vitex negundo var. heterophylla becoming the widely distributed shrub species in the warm temperate zone. The temporal and spatial variation of leaf traits are also the adaption to different environment. The different responses to water and light are the reason of niche differentiation between Vitex negundo var. heterophylla and Ziziphus jujuba var. spinosa. Vitex negundo var. heterophylla, Ziziphus jujuba var. spinosa, Amorpha fruticosa, Rhus typhina, and Grewia biloba var. parviflora show different ecophysiological characters, which is very important to species selection for vegetation restoration and succession of shrub layer.更多还原