996 resultados para Populus. popularis


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采用每木测定的方法,对不同坡位小叶杨林及其林下植被生长情况进行了调查和计算。研究表明,坡下部小叶杨生长状态良好,其平均地径、胸径、枝下高和冠幅等参数都明显优于坡中部和上部,以沟谷地带的小叶杨的生长为基点,则坡下部、中部和上部的小叶杨的树高和胸径生长潜力分别为沟谷地带小叶杨的77.53%,34.88%,31.88%和75.59%,39.51%,33.36%,坡下部种植小叶杨更有利于其稳定生长;小叶杨(+沙棘)混交林,其林分的平均树高、地径、胸径及冠幅等生长参数都明显高于纯小叶杨林,混交小叶杨林比纯小叶杨林有更好的稳定性保水保土功能。通过对不同坡位小叶杨林地生长环境因子的分析表明,各因子对造成不同坡位小叶杨林空间差异的贡献程度和行为不尽相同,土壤含水量、有机质、全N和有效N含量的影响最为显著;土壤速效P和速效K在各土壤剖面的表现基本一致,且坡下>坡中>坡上;而pH与其它因子相比则表现出相反的作用和趋势。通过对营造方式小叶杨林地生长环境因子的分析表明,土壤含水量在0-120 cm土层的影响较为显著,但在120 cm土层以下表现完全相反;混交林地的沙棘对大大调节土壤全P、有效N和速效P含量,对小叶杨林生长环境贡献突出...

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能量流动、物质循环和信息传递共同构成了生态系统三大功能。能量是维持生态系统功能与过程的动力,Jordan(1971)认为能量比干物质更能反映出群落对自然资源(特别是太阳能)的利用情况。Long(1934)率先用热值来表示植物所含能量的多少,此后关于植物热值的研究工作逐渐展开。我国的植物热值研究始于20世纪80年代(杨福囤等,1983;祖元刚等,1986),主要集中在海南(林益明等,2000)、福建(林益明等,2004)、广东(任海等,1999)和浙江(郝朝运等,2006)等热带亚热带植物群落以及内蒙古羊草草原(鲍雅静等,2003),但有关黄土高原地区的植被热值研究尚未见报道。子午岭林区是黄土高原主要的天然次生林区,其植被主要是在弃耕地基础上逐渐恢复起来的(邹厚远等,2002)。由于自然因素与人为因素的影响,子午岭的植被在恢复时间上存在较大差异,形成了处于不同演替阶段的各种植被群落类型。本研究选取的6个代表性植被群落分别是沙棘(Hippophae rhamnoides)群落、山杨(Populus davidiana)群落、白桦(Betula platyphylla)群落、油松(Pinus tabulaeform...

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以生长在陕北水蚀风蚀交错带沙地上的人工小叶杨(Populus simonii)和柠条(Caragana korshinkii)为研究对象,采用剖面法调查2个树种的细根分布特征,通过2年土壤水分定位观测研究,初步分析沙地小叶杨和柠条细根分布与土壤水分消耗的关系。结果表明:1)沙地小叶杨和柠条随土层深度增加,细根表面积密度逐渐减小,0~100cm土层分别集中了整个剖面细根总量的63%和95%;2)小叶杨和柠条林地剖面土壤水分与细根垂直分布密切相关,小叶杨和柠条林地土壤水分特征类似,可分为3个层次:0~50 cm土层为速变层,50~200 cm土层为缓变层,200cm以下土层为缓慢衰减层;3)2年观测期内,小叶杨和柠条林地总蒸散量接近,与同期降水量基本持平,而裸沙地土壤储水量增加;4)小叶杨和柠条细根趋于浅表化的分布特征是对沙地浅层土壤经常获得雨水补给适应的结果。研究结果可为水蚀风蚀交错带沙区防护林建设提供理论依据。

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土壤养分的持续供应是生态系统可持续性发展的基础,尤其在土壤贫瘠地区。土壤磷素被认为是干旱区生态系统的潜在限制性养分因子,但目前半干旱区土壤磷素的深入研究很少。针对半干旱区生态系统恢复方式、人工防护林可持续性经营等关键问题,本论文旨在弄清处于半干旱区的科尔沁沙地东南部沙地人工林土壤磷素转化的主导过程及影响因素,并从土壤磷素可持续供应的角度来评价研究区生态系统的可持续发展。 以处于无人为干扰下、立地条件基本一致的科尔沁沙地东南部的有代表性的生态系统为研究对象,包括原生植被榆树(Ulmus macrocarpa)疏林草地,退化草地,油松(Pinus tubulaeformis Carr.)人工林、樟子松(Pinus svlvestris var. mongolica)人工林和小叶杨(Populus simonii)人工林。系统全面的研究了土壤磷素状况及其季节变化,并深入探讨了樟子松人工林土壤磷素转化及其影响因素(林龄、密度、土壤冻融)。主要结论如下: (1)研究区风沙土表层0~20 cm全磷(<0.2 g kg-1)和活性无机磷含量(<3 mg kg-1)都极低,有机磷占全磷的50%以上,是土壤磷的主要组分。凋落物分解、有机磷矿化和微生物周转是有效磷的主要来源,与这些过程有关的土壤的生物过程控制着土壤磷素转化。Ca-P(钙结合的磷酸盐)的溶解也是速效磷的次要来源,而Al-P(铝结合的磷酸盐)和Fe-P(铁结合的磷酸盐)是活性无机磷库。凋落物分解对有效磷供应起首要作用(尤其在人工林中),凋落物分解的年磷归还量是10 cm层矿质土壤有效磷供应量的1.7~3.4倍。 (2)土壤含水量是影响土壤磷素供应的关键环境因子,而冻融作用对土壤微生物磷和活性无机磷含量无显著影响。 (3)与各人工林相比,榆树疏林草地具有高效的养分循环和较强的土壤磷素保持能力,其退化大幅度降低了土壤持水能力和肥力。而在退化草地上营造以针叶树种为主的人工纯林及针阔混交林进一步降低了土壤全磷含量。从土壤磷素可持续供应的角度来看,在干旱贫瘠地区不宜营造高密度的人工林。研究区的植被恢复,应该选取磷素利用效率高,而养分周转较快的植被类型。这样,不需要集中的人为管理,就能使生态系统达到一种自我维持的良性循环状态。 (4)樟子松的生长受到土壤磷素供应的限制,当年生叶片无机磷浓度比全磷浓度能更准确、直接地反映土壤供磷水平的变化。为满足林分的需求,樟子松的根系活动能够增强根际微生物和磷酸酶活性以促进有机磷的矿化,同时能降低根际土壤pH值以促进Ca-P的溶解。随着林分的发展,活性无机磷含量无显著变化,但土壤磷库(主要是总有机磷)逐渐耗竭,有机磷的矿化潜力也逐渐降低。这表明,随着林分发展,磷素对樟子松人工林的限制性逐渐增强。 (5)为保证已有人工林的可持续发展,必须通过间伐、保护地被物、施肥来调节养分需求与归还之间的平衡,维持地力,保证土壤养分的持续供应。其中保护林下凋落物尤为重要。为防止地力衰退,该地区樟子松林的最大密度(以每公顷胸高断面积为密度指标)应保持在24.1~26.6 m2 ha-1。

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探讨全球气候变化的生物学和生态学效应是当今生态学中的热点,研究大气CO2浓度升高对植物-昆虫相互作用关系的影响具有重要的理论和实践意义。本文使用开顶式气室(Open-top chamber,OTC)在野外条件下研究了CO2浓度升高对三种树木(小青杨、白桦和蒙古栎)叶片化学成分含量的影响,以及树木叶片品质变化对一种广食性森林昆虫(舞毒蛾)幼虫取食、生长发育和取食偏嗜性的影响。得出如下结果:(1)CO2浓度升高对3个受试树种叶片中的营养成分及次生代谢物含量均有显著影响,总体表现为氮含量降低,而碳氮比、非结构性碳水化合物、总酚和缩合丹宁含量增加。叶片中的化学成分含量可随时间发生显著变化,不同树种、甚至同一树种不同冠层高度的叶片对CO2浓度升高的响应强度也是不同的。叶片的干物质含量和比叶重对CO2浓度升高的响应不显著。(2)室内非选择性取食实验、室内选择性取食实验以及上树取食饲养方式下的多龄期取食实验,均发现高浓度CO2处理组内舞毒蛾幼虫的生长发育受到显著抑制。但对四龄舞毒蛾幼虫所进行的短期生物测定并未发现不同CO2浓度处理下幼虫的生长发育速率、对食物的取食率和转化率等昆虫营养指标存在显著差异。(3)叶片品质的降低是导致舞毒蛾幼虫生长发育受抑制的主要原因。但是总体上,CO2浓度升高导致的叶片品质变化并未显著影响幼虫的取食率和取食量。(4)舞毒蛾幼虫对不同叶片种类表现出清晰的取食选择性,这种选择性在其幼龄期就可表现出来。幼虫对小青杨上层叶片有最显著的偏嗜性,对蒙古栎下层叶片有最明显的拒食性。但是CO2浓度升高导致的叶片品质变化对舞毒蛾幼虫的取食选择性和寄主偏嗜行为并未产生显著影响。(5)检测出高浓度CO2处理组内舞毒蛾幼虫虫粪中含有浓度更高的植物次生代谢物质(总酚和缩合单宁),这很可能是昆虫整体生长发育受抑制的重要原因之一。

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本文采用热解吸与气相色谱联用技术对沈阳市主要绿化树种银中杨(Populus alba × berolinensis)、垂柳(Salix babylonica)、榆树(Ulmus pumila)、皂角(Gleditsia japonica)、丁香(Syringa oblate)和水腊(Ligustrum obtusifolium)植物源挥发性有机物(Biogenic Volatile Organic Compounds,BVOCs)排放的日变化、季节变化规律进行了观测,并估算了这6种树的BVOCs排放通量;同时采用开顶箱法研究了高浓度CO2(700 µmol•mol-1)、O3(80 nmol•mol-1)及二者复合作用下蒙古栎(Quercus mongolica)和油松(Pinus tabulaeformis)BVOCs排放规律。研究结果如下所示: (1) 6种绿化树种BVOCs的释放具有显著的日变化和季节变化规律,且夜间几乎均不排放异戊二烯。 (2) 不同树种排放的BVOCs组成明显不同,银中杨、垂柳和蒙古栎以排放异戊二烯为主;油松主要释放α-蒎烯;榆树、皂角和丁香以释放柠檬烯为主;水腊在不同时段其BVOCs组成情况变化较大,主要释放异戊二烯、柠檬烯和α-蒎烯;其中银中杨和垂柳的BVOCs释放量明显高于其它树种。 (3) 在实测数据基础上,估算出沈阳市6种主要绿化树种银中杨、垂柳、榆树、皂角、丁香和水腊在自然条件下的BVOCs年排放量分别为104.86tC,168.66tC,3.56tC,1.27tC,4.07tC和1.33tC。 (4) 大气CO2和O3浓度升高条件下,树木BVOCs释放规律和排放物组成受植物种类和生长季的影响;单独提高大气CO2或O3浓度可显著影响树木BVOCs的释放,二者的复合作用对BVOCs释放的影响主要介于两者单独作用的结果之间。

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农田防护林是农林复合系统的一个重要组分,而农田防护林结构是防护林研究的核心,其三维结构的测度就成为防护林结构研究关键的内容。迄今,有关农田防护林二维结构的各类研究及报道较多,但对于三维结构的数学模型研究较少。表面积密度和体积密度的空间函数是表征防护林带三维空气动力学结构的两个重要指标。然而,我国对于防护林带三维结构模型中的树体表面积、体积以及二者在林带空间的分布函数一直没有科学地定义,无法准确反映林带的立体结构对空气动力学效应的影响,成为该研究领域的难点和前沿问题。本研究以主要造林树种—杨树,所营建的防护林带为研究对象,基于实测的杨树树体结构和林带结构配置模式,通过多个典型样带调查和不同径级的标准木树干解析实测数据分析,建立了杨树总表面积/总体积函数、树体不同组分(干、枝、叶)表面积/体积函数以及两者在林带空间上的分布函数等子模型,并求解得到了每个模型所需参数,从而得到适用于描述我国北方典型杨树农田防护林带的三维空气动力结构。同时利用经典物理学的原理,以常用的空气动力学方程为基础,结合林带表面积和体积的数量及空间分布,推导并改进了在防护林带三维结构下空气的运动方程和连续方程。新推导得到的模型不仅考虑了林带表面积同时考虑了林带的体积。并且通过不同林带类型的风洞模拟进行了模型的验证。研究结果发现,利用林带表面积和体积密度空间矩阵Gamma函数的形状参数和尺度参数的综合表达来作为林带防护效果(最小防护距离、最小防护距离的位置以及有效防护距离)的有效表征参数。本研究所得到的模型不但可较为准确地检验干、枝、叶等不同组分对大气边界层流场的影响,而且可揭示林带整体空气动力学特征,同时可表达与杨树林带结构相似的其他树种组成的林带的三维结构,客观地阐明林带的空气动力学机理,从而提高林带作用下的边界层流数值模拟的精度,为合理地调控防护林带结构、充分发挥其防护功能提供依据。

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本文系统研究了沈阳城市森林的布局与结构、城市森林功能、城市森林病虫害发生与树木健康状况和城市自然资源与社会经济状况等指标对沈阳城市森林生态系统健康与管理的影响。同时一,采用2种生态系统健康评价方法对沈阳城市森林生态系统健康状况进行了评价,并提出了沈阳城市森林生态系统健康管理的对策。研究结果如下:1、截至2004年末,沈阳城市森林植被覆盖率已经达到35%,城市森林林地分布基本合理,但需要进一步加强道路林地、居住区林地和城郊大面积生态林建设。2、沈阳城市森林以乔木为主,乔灌株数比为1.7:1,乔灌的覆盖度比约为7:1。3、沈阳城市森林不同类型林地中植物组成不同。公园林地中有74个属,137个种(变种);庭院林地中有53个属,104个种(变种);居住区林地中有45个属,81个种(变种);道路林地中有43个属,94个种(变种);运河风景林地中有75个属,142个种(变种);棋盘山风景林地中有48个属,118个种(变种)。4、公园林地、庭院林地、居住区林地、道路林地和运河风景林地的Shannon一Wiener多样性指数分别为2.78、3.05、3.15、3.18和3.18,均匀度指数分别为0.56、0.66、0.72、0.70和0.64。除了棋盘山风景林地外,沈阳城市森林中栽植总量超过乔木总量5%的乔木树种有7个属,分别为李、柳树、杨树、桧柏、榆树、槐树和银杏,7种树木总量达到了全部乔木总量的82.09%;栽植总量超过灌木总量5%的灌木树种也有7个属,分别为水腊、丁香、李属,小聚、玫瑰、忍冬和连翘,7个属灌木总量达到了全部灌木总量的87.92%。5、公园林地、庭院林地、道路林地和防护林地中OBH<20cm、20cm<DBH<60cm和DBH>60cm树木的比例分别为:57.9%、40.0%、2.1%,49.2%、47.8%、3.0%,65.3%、33.1%、1.6%和64.6%、34.9%、0.5%,表明沈阳城市森林树木的规格总体上偏小。6、经样方调查和CITYgreen模型计算,沈阳城市森林的生态效益约2.0亿USD/yr.。公园林地、庭院林地和风景林地的景观指标相对较高;道路林地和居住区林地的景观效果一般;防护林地的景观效果较差。7、目前已经发现的沈阳城市森林病害约600余种,虫害约700余种,其中杨树主要病虫害39种,柳树的主要病虫害有33种,榆树和槐树的主要病虫害均为,1种。杨柳树腐烂病、光肩星天牛、天幕毛虫、桃红颈天牛和美国白蛾等是近10年来沈阳城市森林中普遍发生和造成严重危害的主要病虫害。沈阳城市森林主要树木的平均健康指数为2.68,处于一般健康状态。8、沈阳城市森林的土壤和水资源状况均不利于树木的健康生长,沈阳的社会经济发展也有待于进一步提高。9、经过生物指示物法(光肩星天牛为生物指示物)、专家权重法、公众问卷调查和对比研究,沈阳城市森林生态系统总体上处于亚健康状态。10、通过对沈阳城市森林资源、管理状况的调查研究和健康状况的评价,本文提出了沈阳城市森林生态系统健康管理的对策,包括合理规划沈阳城市森林林地布局,增加道路林地、居住区林地和城郊林地的面积和植被覆盖率;调整树木种类组成,避免单一或少数树种的大量栽植,提高生物多样性水平;保护大树和古树;增加城市森林管理资金的投入;应用先进技术,采取科学的病虫害防治和植物养护方法,促进树木的健康生长等。This project systematically studied the urban forest ecosystem health and management in Shenyang. The study explored factors, such as urban forest structure, distribution, pests, aesthetic value, ecological benefit, natural resources and socieo-economic status, that affecting the urban forest ecosystem health and management. Two methods were used to evaluate the ecosystem health. This project also proposed Shenyang's urban forest ecosystem health management strategies. The research results can be summarized as follows: 1. As of the end of 2004, urban forest coverage in Shenyang is about 35%, and is in relatively even patch distribution pattern. However, the street trees and roadside forest patches, residential block forest patches should be enhanced. 2. Trees are the major component of the Shenyang s urban forest, followed by shrubs. The quantity ratio of tree to shrub is about 1.7:1, and the coverage ratio of trees to shrub is about 7:1. 3. Species composition varies by location. There are 74 genera, 137 species (including varieties) in the public parks; 53 genera, 104 species (and var.) in the green spaces of the institution (including school), factory, and company; 45 genera, 81 species (var.) in residential blocks; 43 genera, 94 species (var.) in streets and roadside forest patches; 75 genera, 142 species (var.) in the Canal landscape forest patches; 48 genera, 118 species (var.) in the Qipan Mountain recreation forest. 4. The Shannon-Woener indices varies in parks, in institution, factory, and company yards, in streets and roadside forest patches, in residential blocks.there are 2.78, 3.05, 3.18, 3.15, 3.18, respectively; and the evenness indices are 0.56, 0.66, 0.70, 0.72, 0.64, respectively. Besides the Qipan Mountain forest patches, trees of 7 genera, Prunus spp., Salix spp., Populus spp., Sabina spp., Ulmus spp., Robinia spp. and Ginkgo biloba are of more than 5% the total urban trees, respectively. In fact, trees from these 7 genera are about 82% of all trees in Shenyang's urban forests. In terms of shrubs, species of 7 genera, Ligustrum spp., Syringa spp., Prunus spp., Berberis spp., Rosa spp., Lonicera spp., and Forsythia spp. are more than 5% the total urban shrubs, respectively. 88% of all the shrubs in Shenyang s urban forest are from these 7 genera. 5. The diameter class of DBH<20cm, 20cm60cm of trees in parks, in institution, factory, and company yards, in in streets and roadside forests, and in protective forests are 57.9%, 40.0%, 2.1%; 49.2%, 47.8%, 3.0%; 65.3%, 33.1%, 1.6%; and 64.6%, 34.9%, 0.5%, respectively. The result indicated that the DBH is relatively small in Shenyang s urban forests. 6. Using random plots sampling and CITYgreen model calculation, the ecological benefit of Shenyang's urban is about 0.2 billion US dollars per year. The aesthetic value of parks, institution and company yards, and scenary forest patches is relative high; however, the aesthetic value of protective forest patches is low. 7. There are more than 600 types of diseases and more than 700 kinds of insects in Shenyang's urban forest. Among them, Populus spp., Salix spp., Ulmus spp. and Robinia spp., are attached mainly by 39, 33, 11, and 11, difference types of pests respectively. The rot disease of the Populus spp. and Salix spp., and the insects such as, Anoplophora glabripennis, Malacosoma neustria, Aromia bungii, and Hyphantria cunea are major pests in Shenyang s urban forest for the past 10 years. The trees health condition is relatively poor by having the average health index of 2.68 for major species. 8. The urban soil and water resource are not favorable to tree's growth in Shenyang, and so is the socieo-economic status. 9. Through using bio-indicator, professional and public evaluation, and comparision with other urban forests, it can be concluded that the status of Shenyang s urban forest is not very healthy in general. 10. To improve the urban forest ecosystem health in Shenyang, a better urban forest design need to be implemented to enhance the area and vegetation coverage of the street and roadside forests, the residential block forests, and the surburb forest Species biodiversity need to be enhanced by adjust the species composition of urban forest trees to reduce the single or several tree species populations and to plant more varieties. A better fundings for urban forest health management need to be budgeted. Advanced technologies in tree care and scientific measures to control pests need to be adopted to prove better care for plants and to keep trees grow healthfully.

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土壤氮素(N)转化是生态系统关键的生态学过程之一;而土壤N有效性是沙地生态系统生产力和稳定性的关键限制性因子。以科尔沁沙地东南缘樟子松(pinus sylvestris var.mongolica)、赤松(P.densiflora)和小叶杨(populus simonii)固沙林以及草地为研究对象,采用野外试验和室内实验相结合的方法,全面系统地开展了凋落物分解、土壤N矿化、淋溶等过程及土壤N有效性的研究,旨在揭示半干旱区固沙林土壤N转化及其有效性的特征和机制,为沙地植被恢复、重建、管理和评价提供科学依据。主要结论如下:(1)采用网袋法进行凋落物的分解试验,结果表明不同类型凋落物乘量衰减、元索释放、质员变化均存在明显差异,分解第1年供N能力表现为小叶杨>草>樟子松>赤松;(2)采用PVC顶盖理管法和离子交换树脂袋法分别研究了林地和草地土壤N矿化过程,结果表明土壤N矿化速率表现为小叶杨川章子松七赤松>草地,N相对有效性表现为赤松>樟子松>草地全小叶杨;(3)草地和小叶杨林地土壤N潜在性淋济较高,而樟子松林地较轻;(4)土壤容重、pH值、养分、温度、水分、土壤微生物、土壤动物、林下植被等环境和生物因子反映区域土壤N转化及共有效性的一般特征,而强烈的人类干扰是引起生态系统问差异的关键因索:造林有利于提高沙地土壤N积累和有效性,但樟子松造林30年后才有明显效果:放牧地土壤N硝化速率及其有效性明显高于禁牧地,但质量下降,即NH4+-N/NO3--N失衡,不利于植物吸收、微生物调控和环境保护;(5)赤松、樟子松和小叶杨均为研究区固沙造林的可选树种,合理和科学管理有利于维护生态系统N平衡,实现.可持续经营。

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由于森林生态系统的复杂性,过去常用统计回归模型模拟它的各种动态现象。但这样的模型不能揭示森林生态系统的内在规律,故可称之为“黑箱”模型。随着对森林生态系统认识的加深,以及电子计算机技术的广泛应用,用来模仿森林生态系统内在结构与功能规律的各种计算机模型得到了极大发展,从而产生一些不同“灰化”程度的森林动态“仿真”模型。本文建立的阔叶红松林生长与演替计算模型(DOPIDE)就属于这样的“灰箱”模型。KOPIDE(for KOrean PIne'DEciduous mixed forests)是在JABOWA(Botkin, 1972)和FORET(Shugart等,1977)两个模型的基础上建立的,它们都可称为GAP模型。KOPIDE模型共涉及八个树种:红松(Pinus koraiensis)、水曲柳(Fraxinus mandshurica)、紫椴(Tilia amurensis)、春榆(Ulmus japonica)、蒙古柞(Quercus mongolica)、色木(Acer mono)、白桦(Betula platyphylla)、以及山杨(Populus davidiana)。建立该模型的理论基础是森林演替的林窗(CAP)动态理论,它以一年的步长模拟了样地里每株树木的整个生长发育过成(即更新、生长和枯死)。虽然KOPIDE是JABOWA和FORET的直接效仿模型,但它的模拟针对性较强,在模型的结构上有了很大改进。它的运行结果表明,KOPIDE模型在树种生物学特性的描写上、在阔叶红松林动态规律的模拟上、以及在择伐生长的预测上都有较好的可靠性,可用来揭示阔叶红松林长时期的更新、生长和演替规律与特征,也可模拟阔叶红松林的各种经营方式,为决策人提供预测性结果,以供参考。经过KOPIDE模型的反复运行与调试,发现各树种在更新、枯死与林窗大小的关系上很不相同。根据这种现象,可将树种划分为四类:1、在较大的林窗下更新,枯死后不产生大林窗;2、更新不需要林窗,死亡后产生的林窗较大;3、更新需要林窗条件,枯死后不产生林窗;4、不在林窗下更新,死亡后也不产生林窗。尽管这样的建有点绝对化和简单化,但从中可以得出几类树种之间复杂的相互关系网。由此把复杂森林生态系统大范围的动态变化过程视为组成其许多同质或异质小林地单元的动态相嵌。林地单元的同质性,决定了它们动态变化的同步性,从而导致整个林分动态的突性或不稳定性;而林地单元的异质性是决定森林生态系统稳定性的关键性因素。这从另一角度为在东北东部山地和发展阔叶红松林提供了较有说服力的理论基础。

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土壤是人类赖以生存的自然环境和农业生产的重要资源,世界面临的粮食、资源和环境问题与土壤密切相关,目前危害土壤的主要因素是干旱和重金属污染。杨树具有适应性强、生长快和丰产等特性,本论文以青杨组杨树为模式植物,采用植物生态、生理及生物化学等方法,研究杨树对土壤干旱和锰胁迫的生态生理反应以及种群间差异,研究成果可为我国干旱半干旱地区营造人工林、防止沙漠化提供理论依据,也为恢复与重建重金属污染地区退化生态系统提供科学指导。主要研究结果如下: 1. 青海杨不同种群对干旱胁迫的响应差异 干旱胁迫显著降低了两个青海杨种群(干旱种群和湿润种群)生物量积累,包括株高、基径、干物质积累等,通过植物结构的调整,有更多的生物量向根部分配。干旱胁迫还显著降低了叶绿素和类胡萝卜素含量,增加了游离脯氨酸和总氨基酸含量。另一方面,干旱胁迫诱导了活性氧的积累,作为第二信使,激活了抗氧化系统,包括抗坏血酸(ASA)含量和酶系统如超氧化物歧化酶(SOD),愈创木酚过氧化物酶(GPX),抗坏血酸过氧化物酶(APX)和谷胱甘肽还原酶(GR)。这样,杨树既有避旱机制又有耐旱机制,使其在干旱胁迫下有相当程度的可塑性。与湿润种群相比,干旱种群杨树有更多的生物量分配到根部,积累了更多的游离脯氨酸和总氨基酸来进行渗透调节,并且有更有效的抗氧化系统,包括更高含量的ASA 和更高活性的APX 和GR,这些使得干旱种群杨树比湿润种群杨树对干旱有更好的耐性。 2. 喷施硝普钠(SNP)对青海杨阿坝种群干旱胁迫耐性的影响 干旱胁迫显著的降低了青海杨阿坝种群的生长和生物量积累以及叶片相对含水量,还诱导了脯氨酸的合成以进行渗透调节。干旱胁迫下过氧化氢(H2O2)显著累积从而造成对膜脂和蛋白的伤害,使得丙二醛和蛋白羰基含量升高。干旱胁迫下喷施SNP可以减轻干旱胁迫造成的伤害,包括增加叶片的相对含水量,增加脯氨酸和总氨基酸的积累,并激活抗氧化酶系统如SOD,GPX和APX,从而减少丙二醛(MDA)和蛋白羰基(C=O)的积累,但是在水分良好情况下SNP的效果不显著。 3. 青杨不同种群对锰胁迫的生长与形态响应差异 在同一锰浓度下,干旱种群的耐性指数都要高于湿润种群,这表明青杨对干旱和高锰胁迫具有交叉耐性。两个种群的株高,生物量和叶绿素含量都随锰浓度的升高而逐渐下降。就累积浓度而言,0 和0.1 mM 锰胁迫下,干旱种群积累的锰浓度要高于湿润种群,而在高浓度锰胁迫下(0.5 和1 mM),湿润种群要高于干旱种群。在0,0.1 和0.5 mM下,锰大多积累在根中,叶片次之,茎中最少。而在1 mM,锰更多的积累在叶片中。就累积总量而言,在各个锰浓度胁迫下,根,茎和叶相比,两个种群青杨都是叶片累积的锰总量要高于根和茎。两个种群间比较,对照中没有显著区别,0.1 mM 锰胁迫下,湿润种群根中累积的锰要高于干旱种群,而在地上部中,干旱种群要高于湿润种群。而0.5 和1 mM 锰胁迫下,根、叶、茎+叶、根+茎+叶中,锰累积总量都是湿润种群高于干旱种群。锰胁迫下,青杨叶片数和叶面积包括总叶面积和平均叶面积都显著降低。叶片横切面的光学显微观察结果表明未经锰胁迫的栅栏组织的细胞饱满,海绵组织发达、清晰;胁迫后杨树叶片栅栏组织细胞出现不同程度的皱缩,海绵组织几乎不可见,此外还发现输导组织在胁迫下密度变小和分生组织严重割裂等现象。 4. 青杨不同种群对锰胁迫的生理与生化响应差异 青杨两个种群脱落酸(ABA)含量在锰胁迫下都显著增加,干旱种群的增幅更大。三种多胺含量在锰胁迫下显示了不同的响应趋势:腐胺在两个种群的各个锰处理下都增加,亚精胺只在干旱种群中显著增加,而精胺除了干旱种群在1 mM 下有所增加外,在锰胁迫下变化很小。谷胱甘肽含量随锰浓度升高而增加,在0.5 mM 锰时达到最高值,1mM 时有所下降。植物络合素(PCs)含量与非蛋白巯基(NP-SH)趋势相似,随锰浓度的升高而增加,且干旱种群中含量要高于湿润种群。锰处理还引起氧化胁迫,表现为过氧化氢和丙二醛含量增加。SOD 活性在湿润种群中,在0 到0.5 mM 锰胁迫下活性升高,但在1 mM 锰胁迫时,其活性有所下降。而在干旱种群中,SOD 活性变化较小,并始终维持在一个较高的水平。APX 活性在两个种群中都随锰浓度的升高而增加,干旱种群活性要高于湿润种群。锰胁迫还显著增加了酚类物质的含量,同时GPX 和多酚氧化酶(PPO)活性也随锰浓度的升高而增加。干旱种群的酚类含量和GPX 与PPO 活性都要高于湿润种群。锰胁迫还改变了氨基酸的含量和构成,根据锰胁迫下浓度变化的不同,可以将游离氨基酸分为三组:第一组包括,谷氨酸,丙氨酸和天门冬氨酸,这一组氨基酸含量在锰胁迫下有所下降。第二组包括缬氨酸,亮氨酸和苏氨酸含量在锰胁迫下基本不变化或变化很小。剩下的氨基酸为第三组,这组氨基酸含量在锰胁迫下显著增加,而根据增加的幅度又可以将它们分为两个亚组,丝氨酸,酪氨酸,苯丙氨酸,组氨酸和脯氨酸,在1 mM 下的含量是对照的4 倍以上。异亮氨酸,赖氨酸,精氨酸和甘氨酸含量在1 mM 下是对照含量的2 倍以下。同时,同一锰浓度下,干旱种群比湿润种群积累的氨基酸含量要高。 Soil is the indispensable environment for human survival and important resource foragriculture development. Food and environmental problems facing the world are all closelyrelated to soil and nowadays it is threatened by many factors, among which drought stress andheavy metal pollution are the most serious ones. Poplars (Populus spp.) are importantcomponents of ecosystem and suitable as a source of fuel, fiber and lumber due to their fastgrowth. In this study, different populations of Section Tacamahaca spach were used as modelplants to investigate the adaptability to drought stress and manganese toxicity and differencesbetween populations from dry and wet climate regions. Our results can provide theoreticalevidence for the afforestation and prevention of desertification in the arid and semi-arid areas,and also can supply scientific direction for the reconstruction and rehalibitation of ecosystemscontaminated by heavy metals. The results are as follows: 1. Differences in ecophysiological responses to drought stress in two contrastingpopulations of Populus przewalskii Drought stress not only significantly affected dry mass accumulation and allocation, butalso significantly decreased chlorophyll pigment contents and accumulated free proline andtotal amino acids. On the other hand, drought also significantly increased the levels ofabscisic acid and reactive oxygen species, as secondary messengers, to induce the entire set ofantioxidative systems including the increase of reduced ascorbic acid content and the activities of superoxide dismutase, guaiacol peroxidase, ascorbate peroxidase and glutathioneredutase. Thus the combination of drought avoidance and tolerance mechanisms conferredpoplar a high degree of plasticity in response to drought stress. Compared with the wetclimate population, the dry climate population showed lower dry matter accumulation andallocated more biomass to root systems, and accumulated more free proline and total aminoacids for osmotic adjustment. The dry climate population also showed more efficientantioxidant systems with higher content of ascorbic acid and higher activities of ascorbateperoxidase and glutathione redutase than the wet climate population. All these made the dryclimate population superior in adaptation to drought stress than the wet climate population. 2. Effect of exogenous applied SNP on drought tolerance in Populus przewalskii Drought stress significantly increased hydrogen peroxide content and caused oxidativestress to lipids and proteins assessed by the increase in malondialdehyde and total carbonylcontents, respectively. The cuttings of P. przewalskii accumulated proline and other aminoacids for osmotic adjustment to lower water potential, and activated the antioxidant enzymes such as superoxide dismutase, guaiacol peroxidase and ascorbate peroxidase to maintain thebalance of generation and quenching of reactive oxygen species. Moreover, exogenous SNPapplication significantly heightened the growth performance of P. przewalskii cuttings underdrought treatment by promotion of proline accumulation and activation of antioxidant enzymeactivities, while under well-watered treatment the effect of SNP application was very little. 3. Morphological responses to manganese toxicity in the two contrasting populations ofPopulus cathayana High concentration of manganese caused significant decrease in shoot height andbiomass accumulation. The tolerance index of the dry climate population was significantlyhigher than that of the wet climate population, suggesting the superior Mn tolerance in theformer and the existence of cross-tolerance of drought stress and high Mn toxicity. Injuries tothe leaf anatomical features were also found as the reduced thickness in palisade and spongyparenchyma, the decreased density in the conducting tissue and the collapse and split in themeristematic tissue in the central vein. As for the Mn concentrations in the plant tissues, under0, 0.1 and 0.5 mM, most of the Mn accumulated in the roots, then leaves, and stem the least, while under 1 mM, most of the Mn accumulated in the leaves. As far as the total amounts ofMn extraction are concerned, the leaf extracted more Mn than the root and stem in the twopopulations under various Mn concentrations. There is no difference between the twopopulations under control. Under 0.1 mM, the wet climate population extracted higher Mn inthe root than the dry climate population, while in the shoot, the dry climate populationextracted much more Mn. Under 0.5 and 1 mM, the wet climate population translocated moreMn both in the root and the shoot than the dry climate population. 4. Physiological and biochemical responses to manganese toxicity in the two contrastingpopulations of Populus cathayana Mn treatment resulted in oxidative stress indicated by the oxidation to lipids, proteinsand DNA. A regulated network of defence strategies was employed for the chelation,detoxification and tolerance of Mn including the enhanced synthesis of ABA and polyamines,the accumulation of free amino acids, especially His and Pro, and the activation of theenzymes superoxide dismutase and guaiacol peroxidase. Contents of non-protein thiol,reduced glutathione, phytochelatins and phenolics compounds and activities of superoxide dismutase, guaiacol peroxidase and polyphenol oxidase also increased significantly forantioxidant or chelation functions. The wet climate population not only accumulated lessabscisic acid, free amino acids, phytochelatins and phenolics compounds, but also exhibitedlower activities of superoxide dismutase, guaiacol peroxidase and polyphenol oxidase thusresulting in more serious oxidative damage and more curtained growth.

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青杨组(Section Tacamahaca Spach)杨树是我国重要的乡土经济树种,目前对其分子遗传变异和系统进化的研究还很少,尤其是在青杨组杨树遗传资源极为丰富的川西地区,杨树的分子进化及亲缘关系的研究极为缺乏,非常不利于该树种遗传资源的开发和利用。本研究从川西地区收集了青杨(Populus cathayana)、青海杨(P. prezewalskii)、滇杨(P. yunnanensis)、康定杨(P. kangdingensis)、西南杨(P. schneideri)、小叶杨(P.simonii)和三脉青杨(P. trinervis)这7 个青杨组树种的10 个群体,利用多种分子标记手段对其种间的亲缘关系进行比较,并结合形态和地史资料进行了全面的研究和评价,得到了如下的主要研究结果: 1. SSR 和ISSR 位点变异丰富。通过10 对引物对50 个杨树个体的DNA 样品进行了SSR 分析,所有位点展现了丰富的群体间和种间的多态性,多态位点率达到了100%,每位点的等位基因数变化范围为5 ~ 17,平均为11.9 个;通过11 条ISSR 随机引物对供试的混合DNA 样品进行分析,共检测到130 个标记,其中多态性标记为119 个,多态百分率为91.5%。研究认为,SSR 单个标记能展现高水平信息,而ISSR 单个引物能探测更多数量多态性。通过两个标记的遗传距离、聚类图和PCA 分析,表明:同一种内不同群体间的同源性最高;康定杨和西南杨有较近的亲缘关系;小叶杨和三脉青杨聚合在一起,显示了其相互较近的亲缘关系;滇杨与其它杨树种可能存在着较远的亲缘关系。 2. 采用4 对选择性引物对7 个青杨组杨树种10 个群体进行AFLP 分析,总共扩增出284 个位点,其中200 个位点显示出了多态性,多态位点百分比为70.4%,平均多态带为50 条。TE-AFLP 的分析总共扩增出192 个位点,其中139 个位点显示出了多态性,多态位点百分比为72.4%,平均多态带为34.7 条。比较的结果表明AFLP、TE-AFLP 的遗传信息含量比较接近,略小于ISSR,大约仅为SSR 的1/3;但这两个基于AFLP 的标记系统的信息探察能力也远大于ISSR 和SSR 标记系统。这两个分子标记的聚类结果,显示小叶杨、三脉青杨和滇杨三个种聚为一组,其中小叶杨与三脉青杨的亲缘关系更近;其它几个杨树种聚为一类,西南杨与青杨表现出较近的亲缘关系。 3. 所有7 对cpSSR 引物中,仅有4 个叶绿体位点在种间具有多态性,而在种内群体中并不具有多态性,共检测出13 个条带,组合成了4 种不同的单倍型;对于cpDNA的5 对引物,共检测出了73 条酶切片段,其中52 条是多态带,组合成了9 种不同的单倍型;而5 对mtDNA 通用引物未能检测出多态性的条带,表现出线粒体的保守性。叶绿体的聚类分析认为,小叶杨、三脉青杨和滇杨有较近的母性起源,且依次聚合;其余四种杨树聚为一类,并且康定杨与西南杨表现出最近的亲缘关系,并依次与青杨和青海杨聚合。 4. 根据本文的分子数据,结合形态和生境分布资料分析认为:青杨组杨树种内群体间的遗传变异程度是小于种间的遗传差异,显示了与传统分类一致的结果;三脉青杨和小叶杨有很近的亲缘关系,可能拥有相同的祖先类群;滇杨与小叶杨和三脉青杨之间具有一定的亲缘关系,特别是在其母性祖先的起源上有着一定的同源性;西南杨与青杨和康定杨均保持着较近的亲缘关系,且有可能是这两个种原始祖先杂交后所形成的。 Although western Sichuan is regarded as a natural distribution and variation center forthe Section Tacahamaca of the Populus species in China, little is currently known about themajority of poplar species occurring in this region. In the present study, molecular data wereutilized to determine the genetic relationships among Populus species in Section Tacamahacain western Sichuan including P. cathayana, P. prezewalskii, P. yunnanensis, P. kangdingensis,P. schneideri, P. simonii and P.trinervis. The results are as fellows: 1. The genetic variation at SSR and ISSR loci was abundant. All the 10 SSR loci werepolymorphic, and the number of alleles per locus varied from 5 to 17 with a mean valueequaling 11.9. Based on the 11 ISSR primers, 130 clear and reproducible DNA fragmentswere generated, of which 119 (91.5%) were polymorphic. Our results reveal that single SSRlocus can present more genetic information, while more polymorphic bands can be detectedby single ISSR primer. Moreover, the genetic distance, cluster and PCA analysisdemonstrated that: a close relationship among accessions of the same species and suggestedmonophyly in P. przewalskii and P. cathayana; P. schneideri is genetically highly similar to P.kangdingensis; P. trinervis and P. simonii have a close genetic affinity; P. yunnanensis isdistinct from the other species. 2. Genetic relationships of poplar species in Section Tacamahaca from western Sichuanwere evaluated by means of AFLP and TE-AFLP. For four AFLP primer combinations, atotal of 284 bands were obtained of which 200 (70.4%) were polymorphic with the average of50 polymorphic bands. For four TE-AFLP primer combinations, a total of 192 band wereobtained of which 139 (72.4%) were polymorphic with the average of 34.7 polymorphicbands. Our results indicate that the genetic information of AFLP is similar to that ofTE-AFLP, and little less than that of ISSR, but only about 1/3 of that of SSR. However, theability of information detection of the two AFLP-based markers is much higher than that ofISSR and SSR. In addition, the cluster analysis of AFLP, TE-AFLP and combined data revealthat: P. yunnanensis, P. trinervis and P. simonii clustered together, and P. trinervis and P.simonii showed more closed affinity; the other four poplar species clustered together, P.cathayana and P. schneideri showed more closed origin especially. 3. The cpSSR analysis for seven Populus species belonging to the Section Tacamahaca.Four out of the seven analyzed chloroplast loci were polymorphic, whereas none of the lociwere polymorphic across the accessions within a species. 13 bands and 4 different kinds ofhaplotypes were reduced. Based on 5 pairs of cpDNA primers, 73 fragments (52 polymorphic)and 9 kinds of haplotypes were produced. However, none of the polymorphic was detected bythe 5 mtDNA primer pairs, revealing conservation of mtDNA region. The cluster analysis ofcpDNA revealed that: similar maternal phylogeny among P. yunnanensis, P. trinervis and P.simonii; the other four species clustered together, P. schneideri and P. kangdingensis showedmore closed maternal lineage especially. 4. Our molecular data, morphological characters and nature habitat revealed that: sameto the traditional taxonomy assignment, genetic variation within a same Populus species islower than that among Populus species in Section Tacamahaca; P. yunnanensis may share itschloroplast ancestor with P. trinervis and P. simonii; moreover, sister genetic relationship of P.trinervis and P. simonii indicated their similar origin; P. schneideri clustered with P.kangdingensis and P. cathayana, respectively, and may have derived from an ancienthybridization event involving the ancestors of the two species.

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在水分胁迫条件下,研究了NO供体硝普钠(SNP)对乡土树种小青杨(Populus pseudo-simonii Kitag)和速生品种欧美杨107(Populuseuramericana cv.“74/76”)气孔运动及光合作用的影响。结果表明,经不同浓度SNP处理后,杨树叶片气孔相对开度降低,叶片气孔导度降低,蒸腾作用减弱;NO对杨树叶片的光合作用具有双重性,一定浓度的SNP可以调节植物的光合作用,缓解干旱胁迫的伤害,浓度达到2.0mmol.L-1时,则会产生伤害。SNP对107杨的作用效果优于小青杨,表明SNP更有利于提高速生杨对干旱胁迫的气孔反应能力。

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长白山次生杨桦林是该地区阔叶红松林经皆伐和火烧等破坏后恢复形成的主要次生林类型之一,是阔叶红松林次生演替系列中的重要阶段。参照巴拿马巴洛科罗拉多岛(Barro Colorado Island,BCI)50hm2热带雨林样地的技术规范,于2005年在长白山北坡的自然保护区内建立了一块5hm2的次生杨桦林长期监测样地,对样地内所有胸径≥1cm的木本植物进行了详细的定位调查。对样地的物种组成与群落结构的分析表明:次生杨桦林样地物种组成丰富,共包括16科28属44种;区系特征明显,北温带成分占主要部分;样地内被监测的树木个体数为20101,不包括分枝的独立个体数为16565;优势树种明显,从个体数、平均胸径、胸高断面积和重要值等分析来看,演替先锋树种白桦(Betula platyphylla)和山杨(Populus davidiana)在群落中占有绝对优势地位,但从径级结构来看,它们的更新却非常差,随着演替的进展,这些先锋树种将逐渐走向衰亡;阔叶红松林中的主要树种如红松(Pinusko-raiensis)和紫椴(Tilia amurensis)等已经在次生杨桦林中占有了一定的比例,林下更新良好,逐渐进入林冠层并最终取代杨桦等成为该森林的优势种;从物种的空间分布格局来看,演替先锋树种和阔叶红松林中的主要树种并没有表现出明显的聚集性分布格局,而其它的小乔木和灌木树种则表现出明显的聚集性分布格局,但与地形并没有表现出明显的相关性,相关结论还需要进一步分析。

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通过温度、水分、PEG和NaCl溶液对荒漠河岸树种胡杨(Populus euphraticaOlivier.)种子萌发和胚根生长的影响研究,结果表明:胡杨种子在10~40℃时萌发率均超过50%;其种子能够在完全水分浸泡情况下萌发生长;在NaCl和PEG-6000溶液胁迫下,萌发率与水势呈显著线性负相关(R2>0.89),并受到温度的微弱影响;水势对种子萌发和胚根生长的抑制作用,在高水势时,NaCl比PEG-6000溶液明显,而在低水势时后者超过了前者;在各种胁迫下,胚根生长都比种子萌发受到的抑制明显。实验结果显示,早期的低盐和充分的水分条件是胡杨幼苗存活的关键。