南岭典型植物群落下表土植硅体特征与群落的关系研究

As the natural boundary of mid-subtropical zone and south subtropical zone, Nanling Mountains in South China are quite sensitive to global climate change in the past and become an ideal area to study the late quaternary vegetation change. However, there are still considerable differences on the understanding of vegetation types and distribution patterns in the last glacial maximum (LGM) of Nanling area based on pollen analysis. Therefore, the other biological proxies should be introduced to verify and supplement the results of the palaeo-vegetation reconstruction in Nanling area based on pollen analysis. And to objectively and scientifically interpret the biological information in sediments, the key is to correctly understand the relationship between biological proxies in topsoil and modern vegetation. So, in this project, phytolith assemblages both in more than 50 kinds of typical woody plants and topsoil and several selected plant communities are investigated. Using morphometry and image analysis, we target to get the characteristic phytolith types of the common woody plants (especially broad-leaved trees) in this region. After this, some characteristic parameters of the top soil phytolith assemblages under different kinds of plant communities (such as the ratio between the woody and herbaceous phytoliths, the percentages of the characteristic phytolith type of a given wood plant, etc.) are determined with mathematical methods to identify different regional community types. Furthermore, a relationship between the phytolith assemblages (in topsoil) and these of a given plant community is investigated to explore the soil phytolith reference for identifying community changes. And then we would get the correction coefficients of different phytolith assemblages. Based on these results, we would like to build a quantitative relationship between the characteristic parameters of phytolith assemblages (in topsoil) and quantitative characters of a given plant community to further explore the representative of topsoil phytoliths to its aboveground plant communities. These results would provide reliable analogues for phytolith assemblages from palaeoecological contexts in the Nanling region and be conducive to improving the accuracy of the regional paleovegetation reconstruction.

南岭作为我国中亚热带与南亚热带的分界线，是开展晚第四纪植被变化研究的理想区域。然而目前基于孢粉的南岭末次盛冰期植被类型的认识仍存在较大分歧。故该区古植被重建中需引入其他生物代用指标以对孢粉结果进行验证和补充。而科学解释沉积物中生物信息的关键是正确理解表土中生物代用指标的特征与现代植被的关系。为此，本项目以植硅体为主要手段，拟对该区50余种典型木本植物、典型植物群落及相应表土的植硅体特征进行鉴定统计，确定常见木本植物植硅体的特征型，探索区分不同植物群落的特征植硅体参数，明确鉴别不同群落的表土特征植硅体参数的分布区间。同时，通过表土及其地上群落植硅体组合关系的研究，结合植硅体-植被指示性参数，探索表土植硅体对上覆群落的指示性，计算不同类型植硅体的校正系数。并建立校正后的表土特征植硅体参数与群落数量特征的定量关系，进一步探索表土植硅体对地上植物群落的代表性，为探讨南岭地区的古植被演变提供依据。

南岭作为我国中亚热带与南亚热带的分界线，是开展晚第四纪植被变化研究的理想区域。但该区古植被的定量重建工作较为缺乏，而科学解释沉积物中植被信息的关键是正确理解表土中植被代用指标的特征与现代植被的关系。因此，本项目开展了南岭地区典型植物群落下表土植硅体特征与群落关系的研究。依据项目实施方案，本项目组在南岭地区共布设了39个采样点，采集木本植物单种60种，调查和采集群落样品194个，同时，采集表土样品194个。在对样品植硅体鉴定与统计的基础上，结合主成分分析、判别分析等数学方法，对实验数据进行了分析讨论，取得了三方面的重要认识。首先，本项目组研究了南岭地区常见的阔叶类木本植物植硅体的形态类型，定量区分了常绿阔叶类和落叶阔叶类木本植物以及阔叶类不同科木本植物（壳斗科、樟科、木兰科、蔷薇科、漆树科和大戟科），总结了阔叶类木本植物植硅体的特征型，并将其应用于表土中，判别出了表土中植硅体的木本植物来源。其次，在对典型植物群落及其相应表土植硅体组合特征探究的基础上，提出了识别不同植物群落的表土特征植硅体参数——木本覆盖指数，并修订了常见表土植硅体指数，形成了适合该区的新的温暖指数。木本覆盖指数在草本群落表土、灌丛群落表土以及乔木群落表土中的取值范围依次为0-0.18，0.18-0.29，>0.29；温暖指数可判别落叶阔叶林群落表土（0-0.73）、常绿/落叶阔叶混交林群落表土（0.73-0.78）和常绿阔叶林群落表土（>0.78）。最后，基于表土植硅体—植被指示性参数，定量界定了南岭地区草本群落、灌丛群落和乔木群落表土中不同植硅体类型的植被指示性，并对表土植硅体的数量进行了校正。校正后的表土植硅体能够较准确地指示现生植被的群落信息，如地上植物群落的盖度、群落总生物量及枯落物生物量等。