海南东岸热带滨海森林群落植物多样性恢复与维持对台风的响应

The restoration and coexistence mechanism of plant diversity are receiving increasing attention by ecologists in recent years. However, it’s also perplexing of the response of environmental factors such as typhoon in coastal forests. For example, there were 2-3 times typhoons a year in Hainan Island from the eastern regions to the central and western regions. So the destruction of forests in eastern regions were more than in other regions after typhoon. We think that the restoration and coexistence mechanism of plant diversity in response to typhoon would be more perplexing than other environmental factors and this encouraged our subsequent efforts for investigation. We assume that the plant diversity of forests mainly were depended on the local floristic composition and it always keeps a dynamic equilibrium of population distribution pattern and diversity of forests in a few years after typhoon. But we also assume that plant diversity restoration and maintenance of forests were affected by the forest gap and micro-topographic water conditions, during the dynamic balance of forest destruction and natural restoration after typhoon at the coast regions. We will choose forests on the east coast of Hainan to make experiments for testing these hypothesis: one of the objectives of this research is to investigate relationship between plant composition of east coastal forests and moisture gradient from north to south of Hainan for testing the stability of plant diversity depend on local floristic composition and dynamic equilibrium of population distribution pattern and diversity of forests, other of the objectives of this research is to reveal mechanism of restoration and coexistence of plant diversity in response to the forest gap and micro-topographic water conditions in the forests on the coastal regions of Hainan Island in a few years after typhoon.

多年来，生态学家都在努力解释森林群落植物多样性的形成过程及共存机制等科学问题，但仍需进一步努力。选择一些特殊的森林群落，如常受台风影响的森林群落，从不同角度去解释，或许有事半功倍效果。假设：台风多雨地区，森林群落的植物多样性主要取决于当地植物区系组成；森林总处在受台风破坏与恢复的动态平衡中，台风形成的林隙与微地形环境水分是影响群落植物多样恢复与维持的主要非生物因素。项目拟选受台风影响的琼东部海岸丘陵森林为对象，通过利用固定样地初查与复查、临时样方和路线调查数据，掌握琼东部海岸森林植物组成，结合海岸水热纬度变化规律，探索森林植物组成与当地植物区系的关系，利用固定样地6-7年后的动态变化数据，分析森林植物种群分布格局、多样性维持的动态平衡特点，在森林固定样地内开展台风过后林隙形成、大小形状、群落内部水分因子和幼苗库特征监测，分析群落内植物多样性恢复与林隙等环境因子的关系来验证这一科学问题。

台风对森林结构与植物组成的影响如何？项目选了受台风影响的琼东部海岸及海南其它受台风影响严重的地区的森林（含红树林）为对象，通过利用固定样地初查与复查、临时样方和路线调查数据，分析森林植物种群分布格局、多样性维持的动态平衡特点。结果表明：台风多雨地区，陆域森林群落的植物种类多年基本不变，当地植物区系组成决定着森林的植物组成，反复几年，森林结构虽然受台风破坏，但植物种类变化较小，结构也会逐步得到恢复，处在变化与恢复的动态平衡中，树木的苗木在林隙形成后得到很好的发育，台风经常吹倒一些树木，形成的林隙，改变了微地形环境光线和水分等环境因子，促进了树木苗木的成长。但作用的机理却因不同演替阶段的树木而不同：对演替中早期种，森林过密，对其从幼苗到成树生长及开花结果都不利，如海南苏铁（Cycas hainanensis;）等种群，它喜生于遮光35-60%的森林环境中，需要林窗或相对稀疏林相结构；对演替后期树种来说，如坡垒（Hopea hainanensis）等树种，林窗打开，光线达22%左右（或以上）有利于幼苗的生长。但也有少数量的树木种群退化或发展与台风的影响却没有任何关系，如同时自然杂交种，海南海桑（Sonneratia × hainanensis），其种群的退化是从花粉发育到苗木生长就处劣势，而尖瓣海莲（Bruguiera sexangula . var. rhynchopetala），其种群发育很好，与前者反过来，它们的种群在群落中的动态变化主要取决于自身的生殖生态学特点。同时，我们揭示了红树林的动态变化与长期多年的海平面逐步上升有关，台风影响的短期海水升高对其影响较小。实验结果表明，由于人类基本占用了红树林高潮位线以上的空间，随着海平面上升，低潮位的树种会占领高潮位的空间，高潮位的红树林植物将无空间可退，可能最先消失。实验结果进一步表明，红树林植物全是阳性植物，台风吹出的林隙，有利于红树林苗木生长和发育。台风会对橡胶造成极大的危害，我们的实验结果表明，如果适应混种乡土树木，适当增加人工林的植物组成的复杂性，不仅不影响橡胶的生长，还可以增强橡胶林的抗风能力。