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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]

• The Songnen region was occupied by grassland with stable diversity and cover. • The long-term evolution of the grassland ecosystem was mainly driven by climate. • Plant cover and several dominant taxa were climatically sensitive. Accurate estimates of changes in the composition and diversity of grassland ecosystems, and an understanding of the mechanisms responsible, are essential for predicting future changes and for conservation planning. Here, we synthesize stratigraphic records of phytoliths, together with previously published pollen, diatom, carbonate and grain-size records, from a peat profile (LDBS) in the Songnen region of Northeast China. The results demonstrate that since the mid-Holocene this region was occupied by grassland, with C 3 grasses always dominant but with C 4 grasses progressively increasing. The species richness and plant cover were high and relatively stable for most of the studied interval, but they decreased significantly in the last ∼1,000 years. The long-term evolution of this grassland ecosystem was dominated by climate changes, but it was also affected by human activities and local habitat factors. The plant cover and several dominant plant taxa were climatically sensitive, while the C 4 grasses also responded to changes in the water table and human activities. Species richness was relatively stable but it responded to long-term climatic changes. Phytolith-based reconstruction of Holocene plant community composition and diversity and their driving mechanisms can potentially be used to facilitate conservation planning in this temperate grassland ecosystem. [ABSTRACT FROM AUTHOR]