Study of Jinchuan Mire in NE China Ⅱ: Peatland development, carbon accumulation and climate change during the past 1000 years

摘要

Peat properties including porosity, dry bulk density (DBD), ash content (and their XRD and SEM), TOC, humification and plant macrofossil were measured in the well dated, young peat profiles of Jinchuan Mire in southeast Jilin of China. Base on the properties and depositional rates (Li et al., 2019) of JC1 (50-cm long) and JCA (92-cm long), carbon accumulation rates (RCAs) have been calculated for different periods and processes of peatland development over the past 1000 years have been described. The long term variations of the RCAs between Jinchuan Mire and nearby Baijianghe Mire (Xia et al., 2019) during the past 1000 years matched reasonably well, reflecting similar carbon accumulation rates under the same climatic control even though the plant species could be very different in the two mires. Enhanced detrital content caused by surface runoff due to heavy rains with decline of wood% in plant remains probably reflect wet climates; and vice versa. In comparisons with regional climatic records, we describe the development of Jinchuan Mire as follow: (1) relatively warm and wet climates between 1000 CE and 1150 CE reflected by dominant herb species (> 95%) with low wood% and no Sphagnum%, low DBD and detritus, and high TOC% and porosity. A dry climate occurred during 1150-1200 CE to lower the water table and enable growth of mosses in the mire. (2) Wet and cooling conditions during 1200-1370 CE supported well development of Sphagnum mosses and good development of the mire. (3) A climatic change from wet/cool to cold/dry between 1370 CE and 1440 CE caused disappear of Sphagnum mosses. (4) During the Little Ice Age (1440-1850 CE), cold and dry conditions led to poor peat development without Sphagnum mosses. (5) After 1850 CE, warm and wet conditions were in favor of aquatic herb growth. (6) Human impact caused anomaly peat accumulation with mainly tree species and detritus between 1950 and 1965. The peatland has been recovered from natural condition and development of Sphagnum mosses since 1965. Estimated RCAs in the hummock site and the lawn site are 320 gC/m(2)/y and 63 gC/m(2)/y, respectively during 1970-2010. Estimation of carbon accumulation over the entire peatland needs more work.