全球变化知识资源中心

Mineral soils are usually considered inappropriate for pollen analysis because of the poor quality of pollen and spore preservation and the disturbed stratigraphy. However, here we present a 57 cm core, collected from a waterlogged sandy soil in the lowland Atlantic Forest of SE Brazil, which shows good stratigraphy and good preservation of pollen and spores since similar to 7000 cal. BP, both in organic and in mineral horizons. By the other hand, the decomposition of the organic matter and its translocation along the soil profile led to changes of C and N results (TOC, TN, C/N, delta C-13 and delta N-15). Mid-Holocene paleoclimate inferences from this study are in accordance with climate fluctuations presented in previous studies for Central, Southeastern and Southem Brazil, when a change to more humid climate occurred at similar to 7000 cal BP. The process responsible for the presence of biological proxies along this sandy soil profile involves the continuous deposition of these proxies together with litter and sand, and the subsequent decomposition of the litter. Ultimately, this process led to the vertical accretion of the sand with the more resistant organic structures preserved in stratigraphic sequence. The preservation of pollen and spores along the profile is probably caused by low pH and redoximorphic conditions due to water saturation. This study suggests the potential for retrieving useful paleoecological information from mineral and organic horizons of tropical waterlogged sandy soils, which is especially useful for those regions where traditional pollen archives (lakes and peat bogs) are absent. (C) 2019 Elsevier B.V. All rights reserved.