Holocene wetland developing history and its response to climate change in northeast China

Abstract

Wetland is an important part of terrestrial ecosystem, which plays an important role in maintaining regional environmental stability. With the development of social economy, human activities have led to the wetland extensive degradation and disappearance, which has seriously affected regional ecological security. Restoring wetlands has become the focus of governments and scholars. Understanding the wetland development process and influencing factors in the historical period is an important precondition for establishing reasonable wetland restoration goal. Northeast China is the largest freshwater wetlands area in China, 70% of which are threatened by degradation. Due to the lack of data, the wetland development history and its response to climate change are still poorly documented and understood in this region. Based on this, we systematically analyzed the wetland evolution history in northeast China since the Holocene, and discussed the wetland initiation in different regions of northeast China and examine its links to climate changes during the Holocene. The results show that wetlands started to form at the beginning of the Holocene across northeast China; wetlands began to develop in a large number after 8.6 ka(1 ka=1000 cal.). Nearly 35% of wetlands were initiated in the Holocene optimum; and the majority of wetlands in northeast China were initiated by and developed during the late Holocene, which is very different from the timings for other major northern peatland regions. In the early Holocene, due to the high solar insolation and stronger East Asian monsoon intensity, the climate was warm and humid in northeast China, which promoted the wetlands initiation and development. During the late Holocene, the widespread peatland initiation might have been caused by the cool and moist climate patterns in this region, and this climate combination was not conducive to the decomposition of organic matter and promoted the large-scale wetland development. This pattern confirmed the hypothesis of accelerating initiation and growth of the northern wetlands during the late Holocene. In addition, the results also show that the optimum time and scale of the wetland initiation have shown significant spatial changes in different regions across northeast China since the Holocene, and the temperature and precipitation are the important factors affecting the wetland evolution in different regions. This study will provide some theoretical and data support for the wetland protection and restoration in northeast China in the future.