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树轮导管结构对气候响应的水平和垂直分异特征
Alternative TitleDifferent climate response of xylem vessel structure of tree-ring along horizontal and vertical gradients
韦景树
Subtype硕士
Thesis Advisor李宗善
2019-06
Degree Grantor中国科学院生态环境研究中心
Place of Conferral北京
Degree Name理学硕士
Degree Discipline生态学
Keyword导管结构,定量木材解剖,气候响应,生长衰退,径向生长 vessel Structure, Quantitative Wood Anatomy, Climate Response, Tree Mortality, Radial Grow
Abstract

      气候变化是影响森林生态系统结构和功能的重要因素之一。气温上升诱导的干旱导致树木生长减缓、死亡率增加已成为国际热点研究问题。中国北方半干旱区森林树木生长衰退、死亡事件亦被广泛报道。木质部水力性状塑性响应及其调整对树木缓解环境压力起到非常重要的作用。近年来,定量化木材解剖结构特征结合传统树木年代学在研究树木生长与气候关系具有广泛的应用前景。然而相关
研究在国内还未引起足够重视。
      本文应用树木年代学与定量化木质部解剖结构特征的研究方法,获取径向生长、木材解剖结构特征(导管面积、导管数量、导管总数、水力直径、理论水分传导率等)、气候信息等综合资料,选择中国北方暖温带气候响应敏感区进行样点布设:在水平梯度上,选择黄土高原干旱半干旱区人工刺槐林布设降雨样带;在垂直梯度上,选择北京东灵山半干旱半湿润区天然辽东栎林布设海拔梯度带并
采集树木年轮样品。然后分析树木径向生长、早材解剖结构以及它们对气候的响应的时空变异特征,并对同一地区不同树种气候适应性进行评估,最后阐释全球变化背景下不同树种早材结构的反馈、调整以及水分传输应对气候变化的适应过程。主要结果归纳如下:
    水平梯度上:(i)延安以南地区,气候变暖促进刺槐(Robinia pseudoacacia)细胞扩展,形成直径较大的早材导管以提升水分传导能力,但会增加木质部管孔栓塞的风险,进而引发水力学故障;(ii)水分胁迫加强的延安以北地区,水分亏缺限制了树木的径向生长,导水结构特点亦展现高弹性及调整能力,树木通过产生填充物堵塞导管,以提升水分传输的安全性,体现有效性和安全性的权衡;(iii)然而,延安以北地区,固碳能力和水分传导能力均降低,导致人工刺槐林生产力和生态效益严重受阻。在典型的干旱半干旱区:(iv)羊圈沟小流域本土物种山杏(Armeniaca sibirica)长期维持较弱的导水能力,树木能适应生长季的水分胁迫过程,而引入物种刺槐主要以导水效率优先的策略来提升从根系到叶片的供水能力,这种水分传导策略可能引发水力学故障;(v)在任家台小流域,本土树种辽东栎(Quercus wutaishanica)和引入物种刺槐均通过产生面积大而数量少的导管来应对气候压力,因而这两个树种在未来的气候场景下均可能引发水力学故障。因此,通过对比只有本土物种山杏能较好适应当地的气候条件。
    垂直梯度上:(i)低海拔(1040m)和中海拔(1400m)地区辽东栎主要受到温度上升诱导的干旱胁迫作用,径向生长减缓。木质部解剖特征通过导管面积增加,数量减少的互补性状特征来优先促进水分的传导和提取,因而不存在有效性和安全性权衡;(ii)在高海拔(1800m)地区,树木径向生长未受干旱胁迫的抑制作用,温度上升反而能促进森林的生产能力,木质部解剖结构特征亦通过同时增加导管数量和面积来全面提升水分传输的效率以促进植物的生长,因此体现出气候变暖的正面效应。在北京东灵山中海拔地区,通过4 个不同树种的气候响应和导管解剖结构的对比,结果表明:(iii) 径向生长受到水分胁迫的程度为辽东栎>核桃楸(Juglans mandshurica)>黄檗(Phellodendron amurense)>大果榆(Ulmus macrocarpa);(iv) 辽东栎、核桃楸、大果榆的导管数量随着导管面积的增大而减少,水分传导效率优先,而黄檗的导管面积和导管数量均维持一定的弹性关系,兼具水分传导的有效性和安全性。综合树木径向生长和导管导水特征,大果榆具有较强的耐旱能力,黄檗具有十分合理的水分传输策略;而核桃楸和辽东栎均明显受到水分胁迫的作用,碳积累量呈下降趋势,导管传导效率优先的策略将增加水力学故障的风险。
      刺槐与辽东栎在导管解剖结构上维持相似的特征,但刺槐通过侵填体的生长堵塞导管,降低植物的导水的实际面积/直径,体现出高弹性的应对气候调整能力;而辽东栎无论是在黄土高原半干旱区,还是在北京东灵山中低海拔地区,仍长期维持较高的导水效率,体现出较强的抵抗力,在未来暖干化的背景下,加快树木生长衰退、死亡的命运。
      本研究创新性地在中国北方气候敏感区对树木径向生长和导管解剖特征的水分输导机制,以及它们与气候要素的关系做了探讨;评估了黄土高原降雨样带上和北京东灵山海拔梯度带上的不同树种应对气候变化的能力;初步归纳人了工刺槐林以及辽东栎天然林木质部解剖结构对气候变化的响应机制,对黄土高原生态恢复建设和北京东灵山自然保护区经营和管理具有一定科学指导意义。

Other Abstract

      The warming climate system has long been known as one of the main limiting factors for the establishment, growth, and survival of trees and perpetuation of stable forest ecosystems. The forest decline and tree mortality in Northern China (NC) have also been widely reported where could be confirmed as the sensitive area of climatic change. These mortality events can lead to irreversible changes in ecosystem properties with cascading effects on many physiological and metabolic processes relevant for water, carbon, and nutrient cycles. Nonetheless, the physiological mechanisms of drought-induced forest decline remain poorly understood with the concurrent or alternative role of carbon starvation and hydraulic failure. Plants can alleviate environmental stress through the regulation of physiological processes and the plastic response of functional traits. So far, there still be little focus on the issues of climate change challenges plant capacity to cope with intensified water stress in the temperate forest (including the planted forest) in NC.
In the study, we collected the tree-ring samples at Chinese Loess Plateau and Beijing Dongling Mountain in NC. Combining quantitative wood anatomy with the dendrochronological method. Multi-proxies (radial growth, mean vessel area, number of vessel and theoretical hydraulic conductivity, etc.) were obtained to analyze the interactive relationship between climatological data, radial growth, and wood anatomical features: i) along the precipitation and altitudinal gradient; ii) between different species. Finally, the adjustment of earlywood vessel structure and the hydraulic transport strategy of trees to climate change were explained. The main results are summarized as follows:
      In the horizontal gradient, two patterns of climate-trees growth relationship corresponding with two functional groups regarding the different capacity of hydraulic strategies in xylem features responding to climate variables along a rainfall gradient: (i)increasing trend of both radial growth and hydraulic efficiency in the south and central sites of Loess Plateau; (ii) decreasing trend in radial growth and trade-off between hydraulic efficiency and safety at the north site of Loess Plateau. At the southern Loess Plateau, trees would suffer more risks of hydraulic failure to maintaining large vessels.
      Continued climate change will trigger crown dieback and tree mortality. As for the semi-arid zone at northern Loess Plateau, increasing consequences of water shortage causes of hydraulic dysfunction and restricted radial growth so that forest productivity is strictly limited. In summary, xylem plastic response of climate stress shows the
negative effect on forest growth along the north.south transect; (iii) in the Yangjuangou catchment, Robinia pseudoacacia was strongly suffered by water stress which growth unsustainable in future while native trees were affected by drought weakly which can adapt to the trend of climate change in Chinese Loess Plateau in the semi-arid area. In the typical semi-arid area of Loess Plateau, (iv) the native species of Armeniaca sibirica at the Yangjuangou watershed has maintained a weak water-conducting capacity for a long period. Trees can adapt to the water stress environment in the growing season, and the introduced species of black locust was mainly promoted by the water-conducting efficiency priority strategy which may cause hydraulic failure; (v) in the Renjiatai watershed, the native tree species Quercus wutaishanica and the introduced species black locust respond to climate stress by generating large and small number of vessels,so hydraulic failures can occur at both species in future climate scenarios.
      In the vertical gradient, (i) compared with high elevation, low and mid elevations could be described as drought-prone sites where trees suffer temperature. induced drought significantly and shape a different but complementary manner of xylem features to respond to harsh environment by reducing radial growth and abundance of vessels but increasing vessel diameter. Safety versus efficiency trade.off is not strong,and hydraulic efficiency is more crucial for xylem water transport under prolonged and server water stress environment; (ii) at high elevation, all tree-ring and xylem chronologies, increasing ring width with larger and more plentiful vessels, show a positive relationship with rising temperature suggesting a potential climate. warming advantage for trees xylem counter.balance of water transport and carbon allocation. In the middle elevation of Beijing Dongling Mountain, the under the comparison of different tree species responding to climate change, the results showed that: (iii) the rank of tree suffer from water stress by the order: Quercus wutaishanica> Juglans mandshurica> Phellodendron amurense> Ulmus macrocarpa; (iv) The number of vessels of Quercus wutashanicas, Juglans mandshurica and Ulmus macrocarpa decreased with the increase of the size of vessel, and the water transport efficiency was prioritized. While there was trade-off between efficiency and safety of Phellodendron amurense with the balance along with the number and the size of conduit. According to the characters of climate response and relationship between radial growth and anatomical traits of annual ring, Ulmus macrocarpa had strong drought tolerance characteristics, and Phellodendron amurense had a very flexible water transport strategy; while both Quercus wutaishanica and Juglans mandshurica were obviously affected by water stress with the decrease of carbon accumulation and the risk of hydraulic failure. 
       Long-term series of Robinia pseudoacacia and Quercus wutaishanica maintain similar anatomical characteristics, but the structure of vessel of Robinia pseudoacacia reflected the high elasticity of climate adjustment ability; Whether in the semi-arid region of the Loess Plateau or in the middle and low-altitude areas of Beijing Dongling Mountain, Quercus wutaishanica still maintains high water-conducting efficiency for a long time, showing strong resistance and accelerating forest decline and tree mortality under warming climate.
      In this study, we innovatively made a preliminary discussion on the water transport mechanism of tree radial growth and wood anatomy in the climate-sensitive area of NC. These new knowledge of vessel anatomical features linked between tree acclimation and the physiological performance could provide the implication for ecological restoration and forest management in Loess Plateau of China and the forest management in Beijing Dongling Mountain in future.

Pages103
Document Type学位论文
Identifierhttp://ir.rcees.ac.cn/handle/311016/42313
Collection城市与区域生态国家重点实验室
Recommended Citation
GB/T 7714
韦景树. 树轮导管结构对气候响应的水平和垂直分异特征[D]. 北京. 中国科学院生态环境研究中心,2019.
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