Surface Process
LIU Rui, ZANG Shuying, ZHAO Lin, WU Xiaodong, LIU Lixin, WU Shaoqiang, LI Tianrui, ZHANG Zihao, HE Jianxiang, LI Biao, ZHANG Boxiong, CHENG Xiaofeng
Permafrost is highly sensitive to global changes, and it is important to reveal climate and environmental changes in permafrost regions using vegetation succession. Based on palynological evidence and AMS14C dating from a sediment core, vegetation succession and climate history in the Late Pleistocene of the Mohe Basin (MHB) in the Greater Hinggan Mountain permafrost region was reconstructed. The response of vegetation to environmental changes was further investigated. Results showed that pollen assemblages effectively reflect the vegetation composition in the MHB and surrounding mountainous areas. Based on the relationship between key regional vegetation and climate indicators, vegetation has undergone significant historical changes: from 30.0 to 27.1 ka BP, a meadow wetland landscape showed a cold and humid climate; from 27.1 to 20.5 ka BP, a coniferous forest-grassland landscape indicated a relatively cold and arid climate; from 20.5 to 11.3 ka BP, there was a transition from coniferous forest wetlands to mixed coniferous-broadleaved forest wetlands, indicating the beginning of a warming although the climate remained cold and humid; from 11.3 to 1.9 ka BP, a mixed coniferous-broadleaved forest wetland landscape demonstrated a warm and humid climate; from 1.9 ka BP to the present, a coniferous forest wetland landscape revealed a cool and humid climate. A comparative analysis showed that factors influencing vegetation succession include not only climate conditions related to latitude and land-sea location but also regional factors caused by permafrost itself. Vegetation succession exhibited different response mechanisms to permafrost changes during glacial and interglacial periods. During the Last Glacial Maximum, permafrost expansion benefited the growth of cold and drought-resistant terrestrial herbs with shallow roots such as Artemisia and Chenopodiaceae, leading to the expansion of arid grasslands. During the Holocene Megathermal Period, permafrost degradation provided favorable habitats for vegetation, and also facilitated the formation and expansion of wetlands, promoting the extensive proliferation of aquatic plants, ferns, mosses, and trees, forming a forest wetland landscape. Therefore, permafrost presence enhances the effects of water and heat under different climate conditions on vegetation, making vegetation more sensitive to environmental changes in permafrost regions.