西南边境董棕林调查和研究，兼论河流与山脉的阻隔效应

Caryota obtusa communities are mainly distributed in limestone aspects along rivers in southwestern China bordering to southeastern Asia and southern Asia. The distribution sites are characterized by steep slopes and numerous cliffs, where the vegetation and flora is difficult to explore, and thus, numerous unknown species await to be discovered. Previous studies have shown that there is a high level of endemism of flowering plants in forests in these areas. In these plant communities, the distribution pattern of species is likely affected by rivers and mountains and floristic discontinuities can be considerable across floristic divides, such as the "Tanaka" line or the high altitude Qing-Tibetan Plateau. However, the increased economic value of Caryota obtusa resulted in its overharvesting and the rapid destruction and disappearance of the floristic communities so that numerous endemic and rare species are becoming endangered or even extinct. The study will be beneficial to the establishment of protection and conservation strategies of the unique forests of the limestone regions in southwestern China. The project will focus on twelve study sites along six rivers in south-western China, viz. Brahmaputra, Irrawaddy, Salween, Mekong, Song Hong and The Pearl River. We will carry out our exploration and floristic analysis by means of floristic geography and plant coenology. At each study site, we will choose randomly 12 community plots of 10×10 square meters in size. We will determine the species composition and the structure of communities by a dense collection of samples. This may result in the discovery of new species. Furthermore, we will compare the floristic composition, characteristics and geographical relationships among the diverse sites. Combined with climate and geographical data, we will explore the significance of the topography, i.e. rivers and mountains, on the species composition and levels of biodiversity. The results of this study will provide some further insights into the phytogeographical significance of the "Tanaka" line and the Paleo-Red-River drainage basin as affected by the rise of the Qing-Tibetan Plateau.

董棕林在我国主要分布于西南边境河谷陡峭的石灰岩山地，生境条件特殊，调查难度大，成为物种调查的薄弱地带，许多未知的物种和分布样式有待发现和研究。随着董棕食用和观赏等经济价值的不断提高，董棕林面临日益萎缩和消失的危险，其中的许多特有物种将濒临灭绝。因此，该项目的实施将对董棕林以及西南石灰岩山特殊生境的生物多样性保护提供有力的科学依据。 该项目拟选择分布于雅鲁藏布江、伊洛瓦底江、萨尔温江、湄公河、红河以及珠江六大水系的12个董棕林间断分布点，每个点选择12个10×10平方米的典型群落样方，运用植物区系地理学和植物群落学的方法，开展董棕林的群落和物种多样性调查和研究，采集和发现未知物种，重点分析群落的区系组成、特点和地理联系，并结合相关的地理和气候学资料，分析河流和山脉阻隔对董棕林的物种组成、群落结构和生物多样性的影响，并探讨这种阻隔效应与"田中线"形成、古红河水系的假说以及青藏高原抬升的联系。

董棕林在我国主要分布于西南边境河谷陡峭的石灰岩山地，生境条件特殊，调查难度大，成为物种调查的薄弱地带。随着董棕食用和观赏等经济价值的不断提高，董棕林面临日益萎缩和消失的危险，其中的许多特有物种将濒临灭绝。因此，该项目的实施将对董棕林以及西南石灰岩山特殊生境的生物多样性保护提供有力的科学依据。该项目调查了雅鲁藏布江、伊洛瓦底江、萨尔温江、湄公河、红河以及珠江六大水系的12个董棕林间断分布点，初步确定我国雅鲁藏布江流域至今没有董棕的分布（之前的数据来自标本误定）。该项目的总体成果如下：1. 该项目对我国西南及其邻近国家的董棕林开展了9次野外考察，共设置样方168个10 m x 10 m 样方，采集标本6300号标本，分子材料约4000份；2. 作为董棕的核心分布区，云南红河河谷董棕林由67种乔木树种组成，群落名称可定为董棕+双果桑群落；群落中乔木物种的区系与中南半岛基本一致，且是在强烈的热带东南亚喀斯特地貌大背景下发育形成的，基本阐明董棕林的种类组成、物种多样性和群落结构等特征；3. 在董棕林的野外调查基础上，整理出约 2622种的中国西南董棕林的种子植物名录，其中新发现了约20余种生长在董棕林的未知物种，其中秋海棠科约11种，苦苣苔科约3种，凤仙花科1种，柿树科1种，等等；4.收集了董棕林不同河流的居群材料约491份，其中筛选的230份居群材料已经完成了RAD-Seq的DNA质量检测，以期解释董棕如何响应河流阻隔效应、"田中线"形成、古红河水系的假说以及青藏高原抬升等关键科学问题；5. 在项目整个实施期间，出版相关专著2部；发表论文5篇；另有4篇SCI相关文章已投稿，其中2篇SCI在印，2篇在审；培养相关研究生4位，2位在研，2位毕业；后续的研究成果将陆续整理，在发表时第一标注该项目的课题号。上述成果为董棕林的生态保护以及为董棕的未来园艺开发提供了重要的科学以及和基础数据。