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题名: 横断山区高山流石滩特殊植物生活型的生态适应机制的研究
作者: 杨扬
学位类别: 博士
答辩日期: 2009-01-19
授予单位: 中国科学院昆明植物研究所
授予地点: 昆明植物研究所
导师: 孙航
关键词: 青藏高原 ; 横断山区 ; 高山流石滩 ; 植物特化生活型 ; 棉毛植物 ; 温室植物 ; 垫状植物 ; 水母雪兔子 ; 毡毛雪莲 ; 团状福禄草 ; 适应进化
学位专业: 植物学
中文摘要: 青藏高原东南部横断山区被认为是全球生物多样性最丰富的地区之一。横断山区高山生物带(Alpine life zone,通常被定义为自然树线以上,永久雪线以下的区域)的最前端由于其独特的生态系统和景观而被称为“高山流石滩”(Alpine screes)。受印度洋暖湿季风和独特的地形因素的影响,横断山区高山流石滩孕育了全球最为丰富的高山植物多样性。生长于高山流石滩的植物种类几乎都是该生态系统的特化类群,其中以棉毛植物(Woolly plant),温室植物(Greenhouse plant)和垫状植物(Cushion plant)的三种植物生活型的高度特化适应性状最为显著。由于分布海拔极高,试验材料的可得性和实验设计的可重复性极差,所以在横断山区以生态学理论和研究手段入手,针对上述三种青藏高原特有的植物种类为代表的高山流石滩植物种类的高度特化性状的适应策略和进化机制的研究长期以来一直处于空白状态。 棉毛植物(Woolly plant)特化植物生活型的代表植物种类为菊科风毛菊属雪兔子亚属植物,例如水母雪兔子(Saussurea medusa),雪兔子(S. gossypiphora)和绵头雪兔子(S. laniceps)等。温室植物(Greenhouse plant)特化植物生活型则广泛地见于横断山区极端高海拔生境,例如蓼科大黄属塔黄(Rheum nobile),水黄(R. alexandrae),菊科风毛菊属雪莲亚属苞叶雪莲(Saussurea obvallata),毡毛雪莲(S. velutina)等多种不同科,属的植物种类间。而以石竹科无心菜属福禄草亚属植物团状福禄草(Arenaria polytrichoides)为代表的垫状植物(Cushion plant)则与着生于其表面的多种植物种类建立起了独立于周围裸地的植物小群落。所以,上述三种横断山区极端高海拔生境内最典型的特化植物生活型分别代表了本区高山植物种类在居群以及群落层面上的进化机制和适应策略。本研究选择上述三种特化植物生活型的代表植物种类针对其高度特化性状与横断山区高山流石滩生境内气候和环境因子间的关系及与其他植物种类的关系进行了研究,试图从不同的进化层面认识和理解本区特化植物生活型的适应进化机制和策略,探讨高山流石滩特有植物种类的适应性与横断山系抬升的关系。研究发现: 1、包裹水母雪兔子(Saussurea medusa)头状花序的厚实被毛具有良好的聚热升温作用,且与入射辐照强度密切相关,其升温作用可以加速植物繁殖器官的发育以适应其生境内极短暂的植物生长期; 2、水母雪兔子的厚实被毛结构具有良好的热量缓冲作用。在雨天或是入射辐照强度发生剧烈波动时,完整组植株头状花序内部温度高于处理组植株头状花序内部温度。这一热量缓冲作用为植物繁殖器官的发育提供了一个相对稳定的植物小环境以适应横断山区高山流石滩生境内夏季多云,多雨且波动剧烈的天气特点; 3、水母雪兔子的厚实被毛结构对可见光范围内的入射辐照的反射百分比较高,这可以避免植物繁殖器官受到瞬间高强辐照及其引起的温度瞬间增高可能带来的不利影响。所以,水母雪兔子特有的厚实被毛结构是应对横断山区高山流石滩生境内气候或环境因子特点的长期适应进化产物,其代表的“棉毛植物”是一种横断山区高山流石滩植物种类独有的进化策略和方式; 4、包裹毡毛雪莲(Saussurea velutina)头状花序的半透明,膜质苞片具有显著的聚热增温作用,这一功能主要来自于苞片特殊的解剖结构和对入射辐照的选择透过性。毡毛雪莲苞片的生态适应性体现在增加植物雌性适合度,确保植物繁殖器官快速发育方面; 5、毡毛雪莲苞片的聚热增温效果与蓼科大黄属植物塔黄(Rheum nobile)和水黄(R. alexandrae)十分相似。在苞片的解剖结构和光谱特性方面,上述不同科,属的植物种类也表现出了高度的相似性。所以,以毡毛雪莲,塔黄和水黄为代表的“温室植物”特化植物生活型是横断山区极端高海拔生境内的植物种类在面临相似的选择性环境压力时的一种形态学特征上的“趋同进化”适应策略; 6、“垫状植物”代表植物种类团状福禄草(Arenaria polytrichoides)垫状结构具有协助其它植物种类种子萌发或种苗建成的护理作用,且其护理作用随海拔高度的上升而加强。在气候和环境条件更加极端的高山流石滩生境内,选择着生于团状福禄草垫状结构表面的植物种类及植物个体数目均较低海拔高山草甸生境显著地增加; 7、团状福禄草垫状结构具有的护理特性与其本身的适应进化策略密切相关。团状福禄草垫状特化结构通过其在温度,水分和营养物质含量方面对于周围裸地环境的改造,一方面适应了横断山区极端高海拔生境内的环境和气候特点,同时也为其他植物种类提供了更加适宜的植物小生境; “棉毛植物”,“温室植物”和“垫状植物”三种高度特化植物生活型的进化机制和适应策略从植物居群和植物群落层面代表了横断山区高山流石滩生态系统中植物种类在形态学特征方面的进化路线,同时也包含了本区极端高海拔生境内决定植物形态学适应进化的选择滤过性环境因子和进化驱动力。
英文摘要: The vast Qinghai-Xizang Plateau is often called as the third polar region of the world. The Qinghai-Xizang Plateau is subsequently enclosed within an elliptical circle of mountain ranges, for example, the Himalayas, Kunlun Mountain, and Hengduan Mountain. “Hengduan” Mountain is a Chinese name which means “transverse cutting mountains”, and the region is characterized by formidable high parallel mountain ranges and deep gorges that are aligned roughly north-south. Climatically, the uplift of the Qinghai-Xizang Plateau and surrounding ranges resulted in a monsoon climate in this region that draws wet, warm winds towards the highlands from the nearby sea in summer and dry, cold winds form the highland in winter. Consequently, Hengduan Mountain has become one of the world’s biodiversity hotspots. In the ragged and stony alpine environment of the Hengduan Mountain was commonly name as “alpine screes” which subjected to the high altitudes and a monsoon climate, characteristic dominant factors are general incessant cold rain or sleet and dynamic fluctuations in weather in a single day within short summers. The nature of the environmental factors has resulted in plants evolving rather unique adaptations to live in this region. Among several alpine plants having highly specialized life forms, three types are the most outstanding. Firstly, the “Woolly plant” having the inflorescence entirely covered with long wool-like hairs, such as Saussurea laniceps and S. medusa (Compositae). Secondly, the “Greenhouse plant” characterized by having the inflorescence cover by huge and semi-translucent bracts, such as Rheum nobile, R. alexandrae (Polygonaceae), Saussurea obvallata, and S. velutina (Compositae). Thirdly, “Cushion plant” , which are typically perennials that live for more than 100 years and develop a branched woody rootstock, forming a compact cushion to hemisphere-like structure, such as Androsace globifera (Primulaceae), Arenaria oreophila and A. polytrichoides (Caryophyllaceae). Their specialized morphology provides an opportunity for researcher to investigate the adaptive strategies of alpine plants in this region. The main aims of this study are to understand the ecological adaptability of those three highly specialized plant life forms to the alpine environment in the Hengduan mountain areas from population and community levels. The results show that: 1. Densely hairs covering the inflorescence of Saussurea medusa, one of the representatives of “Woolly plant” act as a heat trap. The warming effects of pubescence on the inflorescence of S. medusa accelerating the growth of the reproductive organ are an adaption to the extremely short growing season in the alpine screes of the Hengduan Mountain. 2. In addition to heat trap, densely hairs on the flower head of S. medusa act as a buffer against rapid fluctuations of temperature and incoming radiations. The buffer effects of hairs on the inflorescence of S. medusa ensuring a warm and constant phyto-climate for the development of inflorescence is an adaptation to the ever-changing weather conditions in the alpine life zone of the Hengduan Mountain. 3. High reflectance (20-40%) of hairs in S. medusa in the PA (photosynthetic active) range protects inflorescence underneath from extremely high incoming radiations which occurred in cloudy days in the high elevations of Hengduan Mountain. Therefore, the unique and specialized morphological feature of “Woolly plant” life form is an adaption to kinds of environmental stresses in the alpine screes of the Hengduan mountain areas. 4. Due to the peculiar anatomical and spectral characteristics, the yellow to red colored bracts in one of the representatives of the “Greenhouse plant”, Saussurea velutina, play an important role in warming up of flower head. The warming effects of bracts in S. velutina ensured seed set. In addition, the warming effects by bracts in S. velutina resulted in the faster growth of reproductive organ compared with manually opened treatment ones. 5. The warming effects and their mechanisms of bracts in S. velutina are almost identical with bracts in Rheum nobile and R. alexandrae (Polygonaceae). Therefore, the semi-translucent bracts in S. velutina, R. nobile, R. alexandrae and other systematically distant taxa inhabiting the alpine screes of the Hengduan Mountain, have evolved as a common morphological adaptation to the fluctuating and extreme weather conditions during the summer monsoonal climate of this region. 6. Cushion of Arenaria polytrichoides acts as nurse plant facilitating the establishment of other plant species on its surface. Positive spatial associations with cushion were more frequent at higher elevations. Therefore, the nurse effects of A. polytrichoides cushions become more pronounced with the increasing elevation. 7. Warmer substrate, greater water content and higher nutritional contents within A. polytrichoides cushions as opposed to outside are possible factors favoring strong plant recruitment on cushions at higher elevations in the harsh alpine environment in Hengduan Mountain. In conclusion, the two plant life forms “Woolly plant” and “Greenhouse plant” can adapt well to the tough environment of the alpine screes in Hengduan Mountain which is contributing to their prominent and highly specialized morphology. Meanwhile, the similarities of adaptive strategy among systematically distant taxa within the same plant life form exhibit the harmonious relationship between plant functions and environments. Additionally, the increasing facilitation by A. polytrichoides cushions at higher elevations seems to be related to the modification of the harsh environmental conditions by cushions of A. polytrichoides. The striking altitudinal variation in association with A. polytrichoides cushions is of importance to clarify the impacts of the uplift of Himalayas on the adaptation and evolution of alpine plants in this region.
语种: 中文
内容类型: 学位论文
URI标识: http://ir.kib.ac.cn/handle/151853/400
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横断山区高山流石滩特殊植物生活型的生态适应机制的研究.杨扬[d].中国科学院昆明植物研究所,2009.20-25
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