孢粉生物群区化与古植被定量重建

BIOMISATION AND QUANTITATIVE PALAEOVEGETATION RECONSTRUCTION

定量重建古植被分布格局不仅可研究古环境本身的演变规律,也为探索其与古气候变化和古人类活动的相互关系、反演古气候变化和古生物地球化学循环,以及校验古植被和古气候模型提供重要的本底数据。孢粉的生物群区化方法(Biomisation)是20世纪90年代发展起来的一种将孢粉数据定量转化为生物群区类型的方法。它主要利用BIOME系列模型中的生物群区类型和生物气候准则,以全球变化研究的植物功能型概念作为纽带,将植物孢粉类群归并到一定的植物功能型中,然后利用关键植物功能型的组合定义生物群区类型,根据某一地点表土和地层中不同孢粉类群丰富度的差异,通过一个模糊逻辑学为基础的客观运算法则计算孢粉谱的相似得分,以此定量重建现代表土植被和古植被类型,最终实现区域和全球孢粉类群到植被类型的转化。本文在已经发表的4篇中文综述的基础上,再次深入介绍了定量重建古植被的孢粉生物群区化方法以及古植被制图的7个操作步骤,包括每一步骤中隐含的注意事项和植物学与生态学资源;简述了为实施Biomisation而设计的Biomise程序运行过程;概括了已发表综述中未涉及到的Biomisation方法的最新发展应用和存在问题,展望了今后在基于孢粉的古植被和古气候重建及其相关领域的研究挑战,包括更新孢粉数据库、加强空白区域的孢粉采样、解决孢粉类群归并为植物功能型的不确定性、重建人类干扰的生物群区以及实现基于孢粉和植被模型的古气候定量反演。

The quantitative reconstruction of palaeovegetation distribution pattern aims not only to investigate palaeoenvironmental evolution,but also to explore the relationships among palaeovegetation, palaeoclimate change and human activities, and to provide important baseline data for reconstructing past climate change and biogeochemical cycles,and for evaluating palaeovegetation and palaeoclimate modeling. The Biomisation, a method numerically transforming pollen taxa and percentage data to biome types,was developed in middle 1990s. According to the global biome classification scheme and its bioclimatic algorithm used in the BIOME family global vegetation models,the Biomisation method assigns pollen taxa to one or more plant functional types and further defines biome types using combinations of key plant functional types. Affinity scores of each pollen taxa and biome are calculated based on fuzzy logic. The pollen sample is assigned to the biome to which it has the highest affinity, subject to a tie-breaking rule. Modern vegetation type and palaeobiome in a site can then be quantitatively reconstructed based on the differences of pollen taxa and their richness in this site. A regional to global biome mapping can then be finally achieved. On the basis of four review articles previously published, this paper introduces again the Biomisation,a numerical technique for palaeovegetation reconstruction and biome mapping, including its ecological principle, operating processes in seven steps, as well as special notes and botanical and ecological resources behind these processes. The Biomise software for performing the Biomisation is further briefly introduced. The newly advances, applications and problems not mentioned in previous review articles are then discussed. Research challenges about palaeovegetation and palaeoclimate reconstructions based on pollen records are finally prospected, including updating pollen databases, increasing the number of pollen sampling sites in some geographical gaps, addressing the uncertainty of assigning pollen taxa to plant functional types,reconstructing the anthropogenic biome, and inversely reconstructing palaeoclimate based on pollen and vegetation models.