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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]

Increasing use is being made of phytoliths for quantitative palaeovegetation and palaeoclimatic reconstruction, and consequently studies of phytolith transport are attracting increasing attention. In this context, we conducted a detailed study of factors affecting the soil phytolith transport in six representative natural soil types in Northeast China. We define a phytolith transport index (T) which indicates that transport rates are the lowest in chernozem and chestnut soils, intermediate in dark brown and albic soils, and obviously higher in black and alluvial soils. Additionally, there are differences in the vertical transport of different phytolith types in the soils; however, the transport characteristics are essentially the same among the different soil types. Transport rates are lowest for tabular and blocky phytoliths, followed by bulliform phytolith. By contrast, the rates for short cell, lanceolate and elongate phytoliths are significantly higher, and, notably, these phytolith types have different size and aspect ratios. The transport of phytoliths is also mainly influenced by mean annual precipitation (MAP), soil pH and soil clay content. Climatic factors, especially MAP, are a more significant factor for phytolith transport than phytolith size and aspect ratio. Overall, our findings are significant for the palaeoenvironmental interpretation of soil phytolith assemblages in topsoils. [ABSTRACT FROM AUTHOR]