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• Assessments are presented of three different methods for quantifying carbon content of aeolian sediments. • The loss-on-ignition method significantly overestimated TOC content for aeolian sediments. • The general wet-oxidation method did not overestimate the TOC content. • Consistent measurements among different methods enable further trend comparisons. • Comparison of different quantification methods for other specific sediment types is proposed. Total organic carbon (TOC) and inorganic carbon (carbonates) are important soil factors and paleoenvironmental proxies used worldwide. During past decades, several different methods have been proposed for determining these parameters from various sediment archives. Although the automatic elemental analyzer is gradually replacing the traditional quantification methods, it is critical to assess the reliability of all currently used methods to ensure accurate regional comparisons, carbon stock estimations and long-term carbon-cycle dynamics modelling. In this study, three most commonly used methods for determining TOC and carbonate content are compared using sediment samples from a sand-paleosol sequence located in northeastern China. Pearson's correlation between results of the different TOC and carbonate quantification methods produced high correlation coefficients, confirming substantial consistency among them. The automatic carbon analyzer yielded more accurate values with smaller uncertainties, while results of the general chemical method and loss-on-ignition (LOI) produced relatively reliable values with more data variability. Meanwhile, combustion at 500 °C to quantify the TOC content yielded significantly higher values than the automatic carbon analyzer and chemical methods, indicating that LOI method is not as reliable as previously thought. We attribute the overestimation to unsuitable SOM to TOC conversion factors and/or the presence of volatile minerals in the samples. In contrast with other studies, chemical wet oxidation of the sand-paleosol sediments did not significantly overestimate TOC, which commonly occurs in modern soils and lacustrine sediments. Our results suggest that the reliability of different methods for measuring carbon content could be affected by the sediment's origin and environment. Assessment of the results of the different TOC and carbonate quantification methods on additional types of sediment is needed so that researchers can use the most appropriate method for their study and make appropriate paleoenvironmental reconstructions given the sediments and methods used. [ABSTRACT FROM AUTHOR]

Understanding local-scale paleoecological processes and their driving mechanisms is a major challenge in plant community ecology. However, phytolith records have the potential to retrieve localized signals of the evolution and patterns of past ecosystems. As a case study, we selected a forested region in Northeast China. We first established a modern phytolith reference dataset which enabled numerical estimates to be made of various aspects of the plant community. We then apply the dataset to a phytolith record from a sedimentary profile (HN) from the Changbai mountain region in order to quantitatively reconstruct the evolution of the vegetation since the last deglaciation. The results of partial least squares regression were used demonstrate that modern phytoliths can quantitatively estimate plant community coverage, species diversity and dry weight ratio; three numerical estimates respectively explained 62.3%, 50.3% and 49.5% of the variance. These quantitative relationships can provide reliable modern phytolith analogues for paleoecological reconstructions. The modern phytolith-based vegetation reconstruction indicates that the Changbai mountain region was dominated by forest communities since the late glacial period. The temporal development of the vegetation can be summarized as follows: boreal or coniferous forest, sparse and species-poor → mixed broadleaf-conifer forest, relatively dense and species-rich → mixed broadleaf-conifer forest, dense and species-rich. The phytolith-inferred changes in plant community coverage, dry weight ratio and species diversity correspond well with climatic changes. This supports the view that the environmental background mainly dominates ecosystem evolution, and it also confirms the utility of phytolith records to resolve local paleovegetation patterns and evolution. [ABSTRACT FROM AUTHOR]