南京紫金山山麓湖泊表层沉积物的孢粉分析*

本研究对南京紫金山山麓玄武湖和前湖共17个湖泊表层沉积物样品进行孢粉分析,旨在获得花粉组合新数据,揭示湖泊表层花粉与现生植被的关系,为开展第四纪湖泊地层孢粉学研究提供现代过程的参考.研究结果表明,花粉组合在剔除非自然分布的种植木本植物干扰花粉外,主要以木本花粉的松属(Pinus)和栎属(Quercus)占优势,其他常见木本植物有枫香属(Liquidambar)、栗属/栲属/柯属(Castanea/Castanopsis/Lithocarpus)、漆树科(Anacardiaceae)等.表土孢粉谱反映了研究区周边山地丘陵针叶、常绿-落叶阔叶林为主的植被,与现生北亚热带森林植被面貌对应良好.此外,陆生草本植物花粉主要是禾本科(Poaceae)和蒿属(Artemisia),湖泊湿生植物如水鳖属(Hydrocharis)、莎草科(Cyperaceae)等含量丰富.玄武湖与前湖中不同样点的主要木本植物花粉表现出优势类型高度一致、含量稳定、受采样位置的影响较小、指示地域植被类型的代表性较强等特点.通过对比南京地区已发表的紫金山及周边丘陵林下表土花粉分析结果,发现湖泊表土花粉组合受局部生境影响小,百分比含量较稳定,故其花粉信息在反映区域地带性植被的稳定性和可靠性方面更具优势.因此,开展表土花粉研究时应优先选择湖泊表层沉积物,藉此可提高基于孢粉重建区域地带性植被的代表性与可靠性.本研究结果为长江下游地区,尤其是南京地区解释第四纪孢粉组合与植被的对应关系提供了新数据和必要的现代过程参考.

Pollen analysis of sediments from the foothill of the Purple Mountain in Nanjing

Based on pollen analysis of 17 samples of surface lake sediments from Xuanwu Lake and Qianhu Lake from the foothill of the Purple Moutain in Nanjing, pollen assemblages are established to reveal the relationship between surface pollen flora as well as modern vegetation and to provide a modern reference for Quaternary pollen analysis of lacustrine sediments. The results show that apart from abundant human-induced woody taxa, Pinus and Quercus are the dominant elements in the pollen assemblages, and other important pollen taxa such as Liquidambar, Castanea?Castanopsis?Lithocarpus, Anacardiaceae occur frequently. The pollen spectrum generally indicates the coniferous and mixed evergreen-deciduous broad-leaved forest in the surrounding mountains and hills, consistent with the present vegetation of northern subtropical forest. In addition, herbs such as Poaceae and Artemisia and lake wetland plants such as Hydrocharis and Cyepraceae are abundant. The dominant types of trees from different samples in Xuanwu Lake and Qianhu Lake are highly consistent; each sample is rather stable in contents; and both are little affected by sampling location. By comparing with existing modern pollen data of topsoil in forests in Nanjing area, we found that the pollen assemblages of the surface lake sediments are characterized by stable percentages of dominant taxa with little influences of local habitats, suggesting their advantages of reflecting regional vegetation. In order to improve the representativeness and reliability of the relationship between regional vegetation and pollen assemblages, this paper highly suggests that surface lake sediments should be preferred to use for pollen analysis in Quaternary pollen interpretation. This paper yields new data and provides necessary modern basis for Quaternary palynological investigation in terms of pollen-vegetation relationship in the lower reaches of the Yangtze River, especially in Nanjing area.