南洛河流域洛南盆地表土孢粉与植被的关系

Relationship between surface pollen assemblage and the vegetation in Luonan Basin, eastern Qinling Mountains, Central China

选取南洛河上游洛南盆地10种植被类型下40处样点表土苔藓开展孢粉与植被关系的研究。结果表明,表土中孢粉组成能很好地反映植被类型。森林表土中乔木植物花粉含量平均值大于40%,且有较高含量的中华卷柏孢子;疏林草原、灌丛群落中乔木植物花粉平均含量分别为13.2%和16.6%,灌木植物花粉相对草丛群落含量较高;草丛群落和农田中乔木花粉平均含量均<10%,草本植物花粉>80%,灌木植物花粉<1%。洛南盆地表土孢粉总浓度平均为1.42×105粒/g,与植被覆盖度关系较弱,而与植被类型有一定联系,能辅助植被类型的辨识。聚类分析和PCA分析都能较好区分森林和非森林植被,前者能较好地区分松林和混交林,后者能较好地区分农田和灌、草丛植被,且比聚类分析更加稳定。松属、栎属等乔木花粉具有较强的扩散能力,能指示区域植被,松属没有表现出很强的超代表性,栎属具有低代表性;蒿属花粉与植被覆盖度间的相关关系较差,具有明显的超代表性,其大量出现与人类的干扰有一定的联系,禾本科花粉具有很好的植被指示性和低代表性,藜科花粉的高含量主要指示了高强度的人类活动;中华卷柏孢子在地层中的大量出现具有指示森林或松林环境的意义。

The catchment of South Luohe River in Central China is a major region for investigating modem pollen-environment relationship because it is an environment transitional zone which is sensitive to the climatic change. In this study, 40 surface sediment samples under 10 vegetation types in Luonan Basin, upper catchment of South Luohe River were taken to investigate the relationship between pollen assemblage and plant vegetation. The results show that the surface pollen compositions reflect the vegetation quite well, with unique features among different vegetation types. In the forest topsoils, the average of arboreal pollen percentage is greater than 40%, and the Selaginella sinensis spore content is higher. As to woodland shrubs and shrubs, the tree pollen average is 13.2% and 16.6% respectively, and the shrub pollen is higher than grass samples. And the grass and farmland topsoils are characterized by the low percentages of tree and shrub pollen （〈10% and 〈1%）, and high percentages of herb pollen （〉80%）. Pinus, Quercus and some other tree pollens can indicate the regional vegetation in terms of their dispersal ability. Quercus pollen is under-representative and so is to Pinus, which is quite different from general. Artemisia pollen is significantly over-represented, has poor correlation with plant coverage, and may reflect human disturbance. Gramineae can indicate plants quite well, but with low representation. High percentages of Chenopodiaceae component probably suggest human activities and predominant Selaginella sinensis may be a significant indication of forest environment. Cluster analysis （CA） and principal components analysis （PCA） can distinguish forest and non-forest vegetation well. The former one is better at separating pine and mixed forests, while the latter one at farmland and other non-forest and more stable than that of the cluster analysis. The first axis of PCA analysis is likely to mainly reflect the humidity. The average of surface pollen concentration in Luonan Basin is 1.42 ×10^5 grains/g. The pollen concentration does not correlate with vegetation coverage, but may help to distinguish vegetation types.