Impacts of the Millennium Eruption and climate change on vegetation species composition of Changbaishan

Large explosive volcanic eruptions can cover wide areas of land with tephra, sometimes with profound hydrological, ecological, and societal impacts. However, while consequences of tephra fallout and flow deposits have been well studied on annual to decadal timescale, little is known about centennial and longer-term changes in vegetation composition. Here, we consider the enduring impacts of the 946 CE Millennium Eruption of the Changbaishan volcano. We reconstruct the pre-eruption vegetation composition based on species, age, and size of carbonized trees recovered from the pyroclastic deposits and analysis of phytolith records in peat cores. Compared with the early 10th century forest composition and structure, the present montane forest hosts a higher abundance of broad-leaved species. Higher elevations, which today are dominated by alpine tundra, were covered in a spruce forest before the eruption. These differences reflect the long process of ecological recovery following the eruption rather than the effects of recent warming, as has been suggested. However, present warming trends are likely to drive the ecological succession towards a reduction of the alpine vegetation zone. Our study emphasizes the importance of interpreting contemporary ecological change in the context of past massive disturbances, together with subfossil evidence of vegetation composition. The millennium volcano eruption rather than climate change primarily alters montane vegetation compositions at Changbaishan, causing larger abundance of broad-leaf forests with tundra dominating at high elevations, based on reconstructive vegetation from deposits and remote sensing data.