西双版纳龙脑香林群落繁殖生物学特性及物候模式

Xishuangbanna endangered dipterocarp rainforest has a strong ecological and biological barrier in Southwest China to compare with lowland dipterocarp forest of Malaysia. Although the long term-phenological observation and their reproductive characteristics especially community-level pattern area remains poorly defined. Though flowering times of plant communities are important life-history components, and it has previously been hypothesized that flowering phenologies may be currently subject to natural selection or be selectively neutral. Thus, changes in various causes of environmental cues and some evolutionary forces are highly responsible to changes in phenological patterns. Climate change, one of the current problems around the globe, is responsible for most of evolutionary significances in terms of reproductive phenology and traits in the majority of the tropical rainforests. Therefore, current research is highly emphasized on phenology, breeding system and pollination system through long-term assessment of Xishuangbanna dipterocarp rainforest communities. Dipterocarp forest may constitute up to 80% of tree emergent individuals, and another fascinating phenomenon is general flowering (mass flowering) and mast fruiting, therefore, only long-term monitoring will determine the general flowering pattern. We have already surveyed the flowering events for five years from 2005-2008 and 2011-2012, thus it is very important to continue the flowering sequence for a next 3 years at least to determine the general flowering pattern, flowering duration, flowering frequency of dipterocarp forest species in the Xishuangbanna regions. We also focused the mating system of dipterocarp forest emergent tree species namely Vatica guangxiensis subsp. xishuangbanaensis a rare, endemic and endangered species, Pseuduvaria trimera and Cleidion brevipetiolatum is a dipterocarp monoecious tree species which can be used by molecular marker allozyme and SSR analytical methods. Therefore, linking reproductive traits and phenological patterns in dipterocarp seasonal rainforests elucidate important measures for conservation of genetic diversity and understanding ecological evolutionary consequences.

本研究拟对龙脑香热带雨林群落的开花物候、交配系统以及传粉系统作一系统研究，以弥补中国热带雨林繁殖生物学研究的空白和亚洲季节雨林此类研究的不足。龙脑香林有80%以上的濒危树种，且龙脑香林因具有"集中开花（general flowering）"的独特现象而备受关注，只有在群落水平上的长期监测才能够揭示"集中开花"格局的成因。在过去的5年时间（2005-2008,2011-2012），已经进行了开花物候及繁殖特性的详细调查研究，在未来3年内继续进行开花物候相关研究对揭示西双版纳地区龙脑香林"集中开花"格局、花持续期及开花频率是非常必要的。同时，应用等位酶及SSR分子标记方法对龙脑香林内代表性植物进行交配系统研究，从而将繁殖生物学特性与繁殖模式相联系，这对于龙脑香季节雨林中遗传多样性保护及进化生态研究是非常重要的研究。通过本项目的研究，可大大提高中国在大尺度生态系统繁殖生物学研究领域中的研究能力。

东南亚的龙脑香热带雨林呈现非季节性气候和多年一次大量开花的物候格局，而这种物候格局被正在进行的全球变化所改变，进而可能对生物多样性造成巨大的影响。在东南亚热带雨林的北缘有十分明显的干季和湿季（21°N）-西双版纳热带龙脑香林的森林物候可能更加容易受到全球变化的影响，但是对于该地区的物候还没有比较完善的数据。本项目连续5年从2011年到2015年对西双版纳热带植物园的20公顷大样地进行了观测，得到了该地区较为完整的物候数据。我们总共对51科，106属，150物种进行了记录，每个物种挑选6个植株，每隔两周访问一次这些植株，观测它们的开花物候。150个物种包括108种树木、42种草本和灌木。结果发现73%(109)的物种是1年开一次花，15%(22)的物种是多年开一次花，5%的物种(8)是一年多次开花， 4%(6)物种一年连续开花，另外我们没有发现3%(5)的物种开花。大多数物种都在干季的结束期或者雨季的开始开花，而果期持续1-6个月，很多都发生在雨季的结束期和干季的开始期(8月到11月)。年季间的物候变化十分明显，和当地气候因子有一定的相关性。优势物种(比例如：Arashorea chinensis, Baccaurea ramiflora, Gironniera subaequalis, Pometia tomentosa, Sloanea tomentosa, Myristica yunnanensis, Knema furfuracea 和 Terminalia bellirica) 开花都不规则，然而大多数的物种都是每年开一次花，且开花时间和果期都是规则的。繁育系统的研究表明大多数物种都是异交的，因此需要传粉昆虫来完成繁殖过程。传粉昆虫的访花频率在年季间变化是显著的(例如: Acanthus leucostychus, Pittosporopsis kerrii和 Parashorea chinensis)，传粉昆虫的访花频率一般在大量开花的年份更高。总的说来，本项目的研究结果表明气候变化(降雨、温度和干旱)显著地影响本地区的繁殖物候格局，传粉昆虫的多度并最终影响到了群落的繁殖成功，这些将对生物多样性产生广泛的影响。