【作者】 郭霄；

【导师】 张新时； 王仁卿；

【作者基本信息】 山东大学 ， 生态学， 2014， 博士

【摘要】 全球变化,包括局部地区干旱及氮沉降等,正变得日益严重。全球环境变化也使得森林光照异质性的发生频率增加。森林植被正面临着前所未有的生存压力,而森林植被将如何采取生理生态学措施适应变化的环境,成为生态学家研究的热点。本研究选取了中国暖温带常见的几种槭属植物：三角枫(Acer buergerianum Miquel),青榨槭(Acer davidii Franch),元宝槭(Acer truncatum Bunge)及栎属的栓皮栎(Quercus variabilis Blume),研究不同的水分、光照及氮沉降对其生长形态、叶形态、叶绿素含量及叶绿素荧光特征、气体交换特征、生物量及其分配格局等生理生态学特征的影响。本研究从功能性状的角度揭示森林植被对水分、光照及氮沉降的响应机制,将有助于理解及预测未来气候变化对森林植被的影响,并能够为植被恢复、森林管理、制定区域生态环境可持续发展战略及暖温带自然资源的开发利用等方面提供基础数据与理论依据。三角枫及青榨槭均为中国本土种。光照及水分是影响森林植被生存及生长的重要环境因子,关于干旱及遮荫相互作用的研究已有许多报道,但是未有一致的结论。关于干旱及遮荫相互作用的几种假设分别认为遮荫能够减轻(“促进理论”)或者加重(“权衡理论”)干旱的负面作用,以及遮荫对干旱的影响没有任何作用(“独立作用理论”)。本实验采用正交设计,共设置了5个水分水平(15%、35%、55%、75%与95%的饱和持水量)及2个光照水平(10%与66%的全光照),对三角枫及青榨槭进行了123天的处理。结果发现,干旱及遮荫不同程度地抑制了三角枫及青榨槭的生长。遮荫显著减少了三角枫的生长指标、生物量指标及叶片尺寸,增加了叶绿素含量、叶片水分含量及比叶面积。遮荫显著减少了青榨槭的生长指标、生物量指标,增加了叶绿素含量、叶片水分含量及比叶面积,但是对叶片大小没有显著影响。干旱显著降低了三角枫及青榨槭的生长指标、生物量指标及叶片尺寸。三角枫总体来说具有更高的可塑性。对大多数测量指标而言,光照及水分的交互作用对两个物种的影响达到了显著水平,因此本研究不支持“独立作用理论”。对两物种来说,在高光照条件下,处在较高的水分状态下(55%-95%的饱和持水量)幼苗生物量往往是干旱环境中幼苗的数倍。而在遮荫环境下,处在较高的水分状态下(55%-95%的饱和持水量)幼苗生物量仅仅略高于干旱环境中幼苗。说明遮荫可以在一定程度上缓解干旱对两树种幼苗的负面作用,本研究基本支持“促进理论”。异速生长分析发现,光照及水分显著影响了三角枫的茎生物量比及叶生物量比,以及青榨槭的茎生物量比,但是对两物种的根生物量比及根冠比没有影响。水分对根冠比的影响不显著也是“促进理论”的特征之一。高于15%饱和持水量的土壤水分含量是保持两物种幼苗生存生长的必要条件,对森林冠幅的常规修剪可以加速幼苗生长,促进植被恢复及群落演替。为了揭示林窗形成对林下不同演替阶段乔木幼苗的影响,采用演替中期种元宝槭及演替后期种栓皮栎作为研究对象,设置了为期一个生长季的盆栽控制实验。实验共有三个处理：(1)持续低光照处理,用以模拟林下环境；(2)持续高光照处理,用以模拟林窗环境；(3)先低光照后高光照处理(光照转换处理),用以模拟林窗的形成。实验过程中对整株及叶片水平的的形态学及生理学指标进行测量,并对光照转换完成后的光照转换处理及持续高光强处理下新长出的叶性状(新叶)进行了测量。相对于持续弱光的情况,光照转换处理下两物种的生物量都有所增加,叶片水分含量、比叶面积及叶绿素含量则有所降低。相对于持续弱光的情况,光照转换处理增加了元宝槭冠幅,降低了根冠比及叶片尺寸。然而,相对于持续弱光的情况,光照转换处理增加了栓皮栎的基径、实际量子产量及光化学淬灭,减少了最大量子产量。不同的光照处理未能改变栓皮栎的生物量分配。两个物种的最大量子产量在光照转换后均急速下降,之后缓慢上升,且元宝槭幼苗的最大量子产量恢复速度快于栓皮栎。持续低光及持续高光处理下,两物种的实际量子产量随时间推移而下降。元宝槭幼苗在光照转换后光照转换处理下新长出的叶片要显著小于持续高光处理下的新叶。但是元宝槭幼苗在光照转换处理及持续高光处理下新叶的叶绿素荧光指标并无差异。栓皮栎幼苗在光照转换处理下的新叶尺寸与持续高光处理下未见差异,而叶绿素荧光显著高于持续高光处理。元宝槭总体上具有更高的表型可塑性,而栓皮栎在叶绿素含量及叶绿素荧光方面的可塑性更高。两种落叶乔木对不同光照的响应机制在光照吸收及利用方面基本相同,但在生物量分配方面有较大差异。不断增加的大气氮沉降极大地影响着森林生态系统及城市生态系统。元宝槭广泛分布在中国北部、朝鲜半岛及日本,且在城市街道、公园及庭院多有种植,具有重要的生态功能及景观价值。在其广泛分布区内,大气氮沉降也具有较大差异。本实验设置了较大跨度的氮沉降速率梯度,从现行的氮沉降速率到未来或能够达到的氮沉降速率,对元宝槭幼苗进行了为期一个生长季的模拟氮沉降处理,并对幼苗的生长、生物量指标及分配、叶形态特征、气体交换及叶绿素荧光指标进行了测量。适度氮沉降促进了株高、基径、总生物量、叶片尺寸、气体交换参数及叶绿素荧光参数然而极端重度氮沉降(20gNm-2y-1)下并未表现出这种促进作用。叶绿素含量、生物量分配格局、叶延展性、叶片水分含量及比叶面积并未受氮沉降影响。氮沉降临界值应该在一定区域,一定时间段内,针对某一特定物种的发育阶段进行定义。氮沉降临界值还应该考虑土壤缓冲能力。本研究中,暖温带种植的一年生元宝槭幼苗中,氮沉降对幼苗生长的促进作用的临界值约为(20gNm-2y-1。总之,三角枫及青榨槭幼苗对干旱及遮荫均具有一定的耐受能力,遮荫在一定程度上缓解了干旱的负面效果。林窗的形成促进了元宝槭及栓皮栎幼苗的生长,总体来看元宝槭幼苗比栓皮栎幼苗具有更高的表型可塑性,而栓皮栎幼苗在叶绿素荧光方面的可塑性更高。适度的氮沉降促进了元宝槭幼苗的生长,而过量的氮沉降速率下,促进作用消失。本研究将为植被恢复中的物种选择提供科学依据,为育种造林及森林管理提供基础数据。更多还原

【Abstract】 Global environmental change, such as regional drought and nitrogen deposition, has becoming more serious and urgent than ever before. Global change also increases the frequency of environmental heterogeneity such as drought and illumination heterogeneity, which has become hot issues in ecology. The plants living in this chaning world are therefore supposed to take steps to adapt to the new environment in prospective climate change scenario, which ecologists also pay close attention to. In this study, we choose several maple trees as the research objects and investigated the effects of various moisture, illuminations and nitrogen depositions on these maples in terms of growth morphology, leaf traits, gas exchange characteristics, chlorophyll contents and fluorescence characteristics and biomass parametrs.As native species, Acer buergerianum Miq.(Trident maple) and Acer davidii Franch (David maple) have large distributions in China. Both species play crucial roles in the forest ecosystem and has high ornamental values. Among all those environmental factors, water and light are two important factors of them, which can limit plant growth and are crucial in sylvicultural practises and in the framework of forest regeneration. Understanding their combined effects on species is fundamental for predicting the effects of global change on forest habitats since environmental factors will change concomitantly. Nevertheless, there is no consensus on how drought interacts with shade. It is variously predicted that shade may have a stronger, weaker or equal impact on seedlings at drought condition by four hypotheses in the recent literature.We performed a potted growth experiment with a wide range of water supply regime [15%,35%,55%,75%and95%of soil field capacity (FC)] combined with two illumination levels (10and66%of full sunlight) to investigate the interactive responses of A. buergerianum and A. davidii to light and water in terms of seedling growth, leaf traits, biomass parameters and partitioning patterns. The experiment was run for123days following the initial acclimation stage. In respect of A. buergerianum, the results showed that shade reduced growth, biomass and leaf size of A. buergerianum to a large extent, but enhanced the chlorophyll content, leaf water content and specific leaf area. Regarding A. davidii seedlings, shade decreased growth, biomass and increased leaf water content, specific leaf area and chlorophyll content, but did not change the size of the leaves. Drought decreased growth, biomass and leaf size of both tree species.For both species, most biomass characteristics partitioning patterns had strong interactions in their responses to illumination and moisture treatments. Leaf traits of A. buergerianum displayed strong interactions in responses to illumination and moisture treatments but not of A. davidii. A. buergerianum owns a higher plasticity than A. davidii. Allometric analysis demonstrated that illumination and moisture influenced stem mass ratio and leaf mass ratio of A. buergerianum and stem mass ratio of A. davidii but had no effects on root mass ratios and root to shoot ratios of both species. The combined effects of light and water differ from simple sum of either factor alone. Shade mitigated the negative effects of drought for both species. In order to keep the seedlings vigorous under various illumination conditions, we recommend a water supply above15%of soil fild capacity. Regulations of forest canopy density would facilitate seedlings growth and accelerate regeneration.In order to uncover the impact of canopy opening in the forest ecosystem, a simulated potted experiment was conducted. We investigated responses of the mid-successional species Acer truncatum Bunge and the late-successional species Quercus variabilis Blume to three solar illumination conditions:(1) low light and low light (LL),(2) high light and high light (HH) and (3) low light to high light (LH). The last treatment was used to simulate canopy opening process. Morphological and physiological acclimations at whole plant and leaf levels were recorded. Both species exhibited increases in biomass, totally and in partly, and decreases in leaf water content, specific leaf area and chlorophyll concentrations when moved to LH treatment. In A. truncatum, sudden exposure to high light conditions (LH) increased crown, and decreased root to shoot ratio, leaf size. However, in Q. variabilis, LH treatment increased stem diameter at ground height, effective quantum yield, photochemical quenching and decreased maximum photosystem II quantum yield. The biomass allocation pattern did not change in Q. variabilis among three conditions. Maximum photosystem II quantum yield underwent a sharp decline and then recovery for both species after sudden exposure to high light, with A. truncatum recovering more quickly than Q. variabilis. In both species, effective quantum yield decreased over time upon LL or HH treatment. Newly developed maple leaves from the LH saplings remained significantly smaller than HH leaves when developing under high light whereas no difference was found in all chlorophyll fluorescence parameters between LH and HH environment. However, the newly developed oak leaves did not display significant difference for mean leaf area and mean leaf perimeter and increased all chlorophyll fluorescence parameters. A. truncatum displayed a greater overall plasticity than Q. variabilis although the oak seedlings have a greater plasticity with respect to chlorophyll content and chlorophyll fluorescence parameters. The two tree species have similar acclimation mechanisms to different light conditions in respect to light absorbing and utilizing, but different strategies in respect to resource allocation.Increasing levels of atmospheric nitrogen deposition have greatly affected forest trees. Acer truncatum Bunge has a large distribution in northern China, Korea and Japan and plays an important ecological role in forest ecosystems. We investigated the responses of A. truncatum to a broad range of nitrogen addition regime with a focus on seedling growth, biomass partitioning, leaf morphology, gas exchange physiology and chlorophyll fluorescence physiology. After the initial acclimation period, the experiment was run from June to September2011. Moderate nitrogen addition promoted shoot height, stem diameter at ground height, total biomass, bulk of leaves and chlorophyll fluorescence and gas exchange performance, whereas extreme level of nitrogen addition did not result in such facilitation. Chlorophyll content, pattern of biomass partitioning, ratio of leaf length to width, leaf water content, and specific leaf area did not change among the addition regimes. The critical amount of nitrogen deposition should be defined in the context of a certain time period in a particular region for a certain species at a special developmental stage. The critical amount of N deposition that weakens total biomass facilitation in A. truncatum planted in mixed soil of yellow cinnamon soil and humic soil is approximately10gNm-2y-1during its first growing season.In summary, all these maple species displayed certain phenotypic plasticity in response to different climate fators, in the level of leaf and the whole plant. Results of this study will provide fundamental and theoretical data to vegetation recovery, forest administration and management and help to predict the responses of forest vegetation in a prosective climate change scenario.更多还原