Late Quaternary vegetation dynamics from central parts of the Madeira River in Brazil

The present study reconstructs the paleovegetation of a varzea (seasonally flooded) forest in the central parts of the Madeira River floodplain in Brazil using palynological data. Forty-nine cut-bank sediment samples from the Madeira River were processed in the study; from these, ten samples contained pollen: two contained pollen from the Middle Pleniglacial age, one contained pollen from the Tardiglacial age, six contained pollen from the Holocene, and one contained more recently deposited pollen. The Middle Pleniglacial pollen belonged to a primary succession varzea forest, while the Tardiglacial pollen represented a late succession varzea forest. On the other hand, the three Holocene samples showed the characteristic composition of chavascal (water-logged forest) or lacustrine varzea forest, and three samples belonged to a late succession varzea forest. The most recent pollen deposit represented a secondary succession varzea forest. This paleovegetation showed a typical mosaic distribution, which may be explained by the fluvial dynamics, high species richness and diversity in the varzea forest, and the presence of dominant species.

本研究依托孢粉数据，重建了巴西马代拉河河漫滩中部泛洪森林（varzea）的古植被面貌。本研究对取自马代拉河的49个岸崩沉积物样本进行了处理，其中10个样本检出孢粉：2个样本采自中冰盛期（Middle Pleniglacial），1个样本采自冰消期（Tardiglacial），6个样本采自全新世（Holocene），另有1个为新近沉积的孢粉样本。中冰盛期的孢粉对应原生演替型泛洪森林，而冰消期的孢粉则代表晚演替型泛洪森林。全新世样本中，3个呈现出chavascal（积水森林）或湖滨泛洪森林的特征组成，另有3个属于晚演替型泛洪森林；最新近的孢粉沉积则对应次生演替型泛洪森林。该古植被呈现典型的镶嵌分布格局，这一特征可通过河流动力过程、泛洪森林极高的物种丰富度与多样性，以及优势种的存在得到合理解释。