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An improved understanding of past interactions between terrestrial vegetation and various forcings, such as climate change, human impact, and paleofire, is crucial for assessing impacts of future global change on terrestrial ecosystems. This study seeks to find the key factor or factors that have driven Holocene vegetation change along the East Asian monsoon margin. Several high-resolution pollen records are reviewed and new phytolith-based paleovegetation reconstructions and physical geochemical datasets are presented from a peatland in northeastern China. Using 108 modern topsoil samples as a training set, canopy cover and vegetation composition are estimated for the period since 5100 cal. yr BP. Variation partitioning analysis (VPA) is used to determine the relative importance of climate change, human impacts, and paleofire disturbance. The generalized dynamic vegetation model LPJ-GUESS is forced with climate anomaly output from an atmospheric general circulation model to simulate vegetation dynamics during the mid-Holocene and the pre-industrial era. The proxy-based estimates are compared to modelling output. Results indicate that regional tree cover varied from 10% to 40% during the past five millennia. The single-core, phytolith-based reconstructions are generally consistent with stacked tree pollen z-scores calculated from different records along the East Asian monsoon margin, implying that mid-Holocene tree cover decrease was persistent and almost synchronous over extensive areas. VPA demonstrates that long-term monsoon marginal vegetation successions were mainly caused by climate effects. Numerical modelling suggests that since the mid-Holocene the retreat of forests along the monsoon margin was primarily associated with precipitation deficits. Our investigation highlights that the precipitation associated with the East Asian monsoon system has exerted a stronger influence than the westerlies on the monsoon margin climate and vegetation change. With ongoing global change, close attention to variations in precipitation patterns and amounts should be especially helpful in efforts aimed at ecological monitoring, change prediction, and restoration. • Phytoliths provide complementary paleovegetation evidence to pollen for the monsoon margin area in northeastern China. • Phytolith-based quantitative tree coverage reconstructions suggest persistent forest cover since the mid-Holocene. • Vegetation dynamics within the monsoon margin area is strongly associated with East Asian monsoon variability. • DGVMs modelling suggests the dominant role of precipitation in regulating vegetation change. [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]