Solar Forcing and ENSO Regulated Rates of Change of Ecosystems in Northeast China Since the Last Deglaciation

Understanding long-term (centennial- to millennial-scale) ecosystem transformation and dynamics is a key factor in the prediction of ecosystems under ongoing climate change. However, the magnitude and patterns of vegetation change on this timescale are poorly understood. The rates and patterns of vegetation change and their driving mechanisms in Northeast China were studied, using a compilation of 33 fossil pollen and phytolith sequences from this region. Rates of change (ROC) of vegetation in Northeast China increased continuously during the last deglaciation, decreased during the early Holocene, reaching their lowest level during the middle Holocene, and increased again in the late Holocene. ROCs were different for forest and grassland during specific intervals, and vegetation stability varied from north to south and from west to east. Attribution analysis showed that climatic factors have been the dominant drivers of vegetation change since the last deglaciation. Natural fires were also important, particularly during the last deglaciation through the middle Holocene; human activities became increasingly important from the middle through late Holocene. ROC of forest vegetation exhibited -1500-yr and - 350-yr periodicities; solar activity was likely the driving mechanism. Grassland ROC showed -500-yr and - 270-yr periodicities, perhaps reflecting ENSO regulation of East Asian summer monsoon intensity.