热带雨林的孢粉垂直分布规律——以海南岛现代孢粉雨为例

热带地区环境变化对研究全球气候变化显得越来越重要，热带地区的古环境记录，特别是孢粉记录是恢复过去气候的重要方法，东亚热带地区在冰期－间冰期的气候影响下，生态环境主要表现为山地植被带的垂直升降，因此，定量恢复热带地区第四纪植被垂直移动的幅度，以及作为古气候的替代性指标进行数量化转换是热带地区孢粉研究的关键，然而，我国热带地区现代孢粉雨和植被的关系研究程度较低，给热带第四纪孢粉古生态的恢复和对比带来困难，本研究较系统地总结了海南岛从低地平原到五指山1860m的垂直植被带表土的孢粉散布规律，为热带地区孢粉古环境的重建提供了新的基础数据。研究结果表明，孢粉组合的变化与垂直植被带紧密相关，孢粉的多样性随海拔升高而降低，其中针叶类随海拔升高而增加，蕨类孢子则相应减少，在低地和低山丘陵，孢粉组合显示出为干扰的影响，如防风雨的主要树种木麻黄（Casuarina)，行道树台湾相思（Acacia richii)和人为砍伐后大面积生长的芒箕（Dicranopteris)群落等在一些孢粉谱中特别高，尽管如此，孢粉组合反映的垂直植被带变化仍然是清楚的，海南岛由下至上可划分出5个表土孢粉组合带－低地人类强烈干扰带（＜400m):Mallotus,Casuarina,Pinus,Myrica,Palmae,Poaceaae,Dicranopteris:--低地质陵地带（400－800m):Quercus,Castanopsis,Mallotus,Myrica,Platea,Meliaceae和大量孢子（包括Dicranopteris);--山地下带（800-1200m):Castanopsis,Quercus,Podocarpus,Dacrydium,Cyathea和单缝孢子；－－山地上带（1200-1600m):Dacrydium,Pinus,Altingia,Quercus,Castanopsis;－－山顶带（＞1600m):Pinus,Rhododendron,Dacrydium,Symplocos.

MODERN POLLEN RAIN IN HAINAN ISLAND, SOUTHERN CHINA: ALTITUDINAL POLLEN DISTRIBUTION IN THE TROPICAL RAIN FOREST

Modern pollen rain study was carried out on the samples collected from Hainan Island, tropical China along an altitudinal gradient from 0-1860 m (from lowland rainforests or savannas to Ericaceae and highland pine forest). The pollen analysis demonstrates that the variation in pollen taxa has a close relation with altitudinal changes of forest communities. Pollen diversity is high in the areas of lowland rain forests, despite that many pollen spectra from < 700 m altitude show a great influences of human disturbance, such as the high percentages of Casuarina, Acacia, Dicranopteris. Pollen dispersal in the mountain rain forests is characterized by the increase in Fagaceae (Quercus and Castanopsis), then upwards in conifer (particularly Dacrydium pierrei, Pinus, Podocarpm imbricatus) and Altingia obovata, and in Ericaceae. The pollen dispersal pattern indicates the distinctive vegetation distribution along an altitudinal and climatic gradient, although the pollen abundance is not dance is not coequal with the forest cover. The present study provides data for interpretation of fossil pollen records from tropical regions in southeastern China, and helps to understand the altitudinal shift of forest belts during Quaternary.