Vegetation history and climate change recorded by stomata evidence during the late glacial in the Great Khingan Mountain Region, Northeastern China

Abstract

The research on the evolution of larch forest is significant to understand the vegetation and climate change in mid-high latitude region of the Northern Hemisphere. However, the pollen records to reconstruct the larch forest are problematic due to low pollen representation caused by severely poor pollen productivity and dispersal. New proxy of microfossils is needed to solve this problem. Using coniferous stomata as a proxy to reconstruct the evolution of conifers has some advantages, such as well preserved, locally deposited, continuously remained in lake sediments and can be accurately identified to the genus level. Therefore, a high-resolution stomata record covering 20.3–10.8 cal ka BP from Lake Moon was presented, in order to reconstruct larch forest history from the Last Glacial Maximum to early Holocene in the Great Khingan Mountain Region, Northeast China. Reference conifer stomata from fresh leaves of the local coniferous species and lake surface samples were prepared for the identification of the fossil stomata. Larix , Sabina and Picea stomata were identified from the sedimentary sequence of Lake Moon, and the results of stomata influx from this study and pollen influx from the previous study indicate that the vegetation evolution has gone through distinct stages. Before 15.0 cal ka BP, no Larix existed in the vicinity of study site. The first arrival of larch is inferred by the continuous presence of stomata at 15.0 cal ka BP, which manifests that the vegetation turned into forest steppe. The coverage of forest increases slightly from 15.0 to 12.8 cal ka BP with an interruption between 14.3 and 14.0 cal ka BP. During 12.8–11.8 cal ka BP, the vegetation were characterized by the expansion of conifers mainly Larix and the shrinkage of broadleaves and herbs. From 11.8 to 10.8 cal ka BP, the vegetation type remained as forest steppe with the shrinkage of conifers dominated by Larix , in conjunction with the expansion of broadleaves and herbs with high vegetation coverage. The establishment of larch forest inferred by the continuous presence of stomata marks the onset of the late glacial in the Great Khingan Mountain Region at 15.0 cal ka BP. The application of stomata analysis provides detailed scenes of coniferous evolution surrounding the Lake Moon. It is suggested that the analysis of fossil stomata is a valuable tool to demonstrate unambiguous evidence for the local presence of the conifers in study region, even better than pollen records when the component of larch is low in vegetation. The evolution of the forest communities in the late glacial period in the Great Khingan Mountain Region is comparable with the vegetation evolution of other regions at different latitudes in East Asian monsoon region, which indicates that the climate change at millennial/centennial scale in late glacial is roughly synchronous in East Asian monsoon region. The series of climatic periods in this study revealed by the stomata and pollen records is also similar to that of Europe, like Meiendorf interstadial, Oldest Dryas cold event, Bolling-Allerod warm phases, Younger Dryas cold event, warm and humid early Holocene. The temperature change is probably the main factor to impact the vegetation change. The study shows that the vegetation succession in the study area is responsive to the temperature change of the Northern Hemisphere controlled by the global ice volume, and reveals the synchronization of the late glacial climate change in the mid latitude region of East Asia and the North Atlantic region.