Lignin Analysis and Carbon Isotope Studies of Plants and Humic Substances in Soils for Exploring Vegetation and Climate Changes in Southern Brazilian Highlands

摘要

The vegetation of southern Brazilian highlands in Rio Grande do Sul State is a mosaic of grassland, shrubland and deciduous forests with the conifer Araucaria angustifolia. There is an ongoing discussion in the scientific community, whether the grasslands represent relics of drier and cooler periods in the Holocene or if they are the result of deforestation in recent times. The present climate is moderate and humid and would favour the expansion of forest if there is no burning and grazing of grassland. We assume that the isotopic and biochemical composition of humic substances in soils reflect the plant specific composition of the biomass entering the soils. Therefore we characterized plant tissues from gramineous and woody species as well as humic substances in soils to investigate, if humic substances can be used as biomarkers for past vegetation and in the broader sense also for climate changes.