【作者】 王传华；

【导师】 李俊清；

【作者基本信息】 北京林业大学 ， 生态学， 2010， 博士

【摘要】 长江中下游地区是我国重要的工农业产区,生态环境相对脆弱。马尾松(Pinus massoniana)林和枫香(Liquidambar formosana)林是本地区最主要的植被类型,对于当地的生态安全发挥着不可替代的作用。在人为干扰持续存在甚至不断加强的背景下,如何对其进行科学的经营管理是当前必须面对的问题,而研究森林的演替趋势,分析重要生态因素对森林演替的影响具有重要的作用。本文采用样地调查法研究了马尾松林、枫香林的群落结构及幼苗更新,用“空间代时间”法构建的枫香伐桩序列研究了枫香萌芽更新的规律；在室内采用控制实验,研究了5个主要乔木树种幼苗对光与氮变化的存活、形态、生理及非结构性碳水化合物的响应,并在此基础上分析了马尾松林和枫香林的动态,研究得到如下结果。(1)该地区的马尾松林中枫香为一个增长种群,马尾松种群为一个衰退种群；而枫香林中的枫香种群不能实现持续的实生更新。马尾松林的马尾松是一个年龄为25-30年的同生群,而枫香则为一个增长种群；马尾松和枫香呈“J”型加速增长；化香和合欢幼苗的高生长速率分别在大级别幼苗出现拐点。(2)枫香的萌芽更新对于枫香种群的维持具有重要意义。本地区的枫香种群由实生更新和萌芽更新的植株共同组成,枫香伐桩具有较高的存活率、其萌芽能够“强自疏”并最终形成1—2杆的萌代主、萌条生长速度远高于实生幼苗的特点,使枫香种群具有较强的萌芽更新能力。(3)枫香种子的非休眠特性、冬季低温及林下弱光环境是影响枫香实生更新的限制因子。马尾松林和枫香林下的凋落物和其它环境因子不影响枫香种子的存活和萌发。(4)N对5个主要树种的存活、生长及形态生理均没有显著影响,光对树种的存活、生长、形态及生理特征有显著影响；5个树种间的耐荫性具有麻栎(Quercus acutissima)>短柄袍(Quercus serrata var. brevipetiolata)>枫香>马尾松>化香(Platycarya strobilacea)的位序。5个树种幼苗相对生长速率RGR (Relative growth rate)在各光强下的位序没有变化,因此不支持“RGR位序变化是群落物种共存机制之一”的假说；5个树种形态对光强的适应不符合“碳捕获速率最大化”假说,耐荫性较强的树种采用低光合低呼吸的策略实现弱光下的碳平衡,暗呼吸速率Rd-mass[Dark respiration rate (mass base)]可以较好地反映植物弱光下碳平衡的能力；植株非结构性碳NSC(Non-structural carbonhydrate)的浓度与物种存活正相关。更多还原

【Abstract】 The middle and lower reaches of Yangtze-river is one of the most important economic districts of China, which also is recognised as an ecologically degraded and frail area that needs to be restored and conserved. Pine (Pinus massoniana) forest and Formosan swwetgun (Liquidambar formosana) forest are the most important forest of this district. To manage these vegetation effectively, a full understanding of their natural succession was essential. In this paper, a series of field work and control experiments in green house was conducted to study the regeneration and succession of these two forest types. The results indicated that:(1)in Pine forests, the population of P. massonaina was a cohort aged from 25 to 30 years, but the population of Formosan sweetgum was as an increasing population; on the other hand, the Formosan sweetgum population in sweetgum forests was a decreasing population; the shoot growth of Platycarya strobilacea and Albizia julibrissin seedlings decreased earlier than pine and Formosan sweetgum. (2) Seedling regeneration and sprout regeneration were coexisted in sweetgum populations. Higher survival of stumps, higher "self-thinning" of existing sprouts and higher shoot growth rate than seedlings are the characteristics of Formasan sweetgum sprouting. (3) Our experiments suggested that non-dormant seed and seedling shade intolerance were the key factors limiting seedling regeneration of L. formosana. We did not find any litter leachate inhibition effect on seed germination and store. (4)Survival, growth, and morphology of Quercus acutissima, Quercus serrata var. brevipetiolata, L. formasana, P. massoniana, P. strobilacea seedlings were strongly affected by PAR (Photosynthetic active radiation), but nitrogen supply had little effects on these traits. The shade tolerance rank among five species was Quercus acutissima> Quercus serrata var. brevipetiolata>L. formasana>P. massoniana>Platycarya strobilacea. Our results also suggested that there was no RGR (Relative growth rate) rank reversal among PAR gradients. The effects of PAR on seedlings functional traits conferring to RGR were different between Q.acutissima, Q. serrata var. brevipetiolata and shade intolerant species L. formasana, P. massonian and P. strobilacea. Shade tolerant species had a higher RMR, but shade intolerant species showed a higher LMR (Leaf mass ratio), LAR (Leaf area ratio), and SLA (Specific leaf area). According to the data that shade tolerant species possessed a lower mass based Amax (Light-saturated CO2 assimilation rate), mass based Rd (Dark respiration rate) and the results of whole plant gas exchange simulation, we concluded that strategies of shade tolerant species under low light environment were low leaf investment, low carbon capture rate and low respiration rate. Our results also revealed that seedling survival was strongly correlated with the NSC (Non-structural carbon) concentration in root.更多还原