Peatlands cover a small portion of the Earth’s land surface but hold ~30% of soil carbon (C) globally. However, few studies have focused on the early stage of peatland development, which is a key stage in the initial C sink function of peatlands. An immature peatland is vulnerable to changes in environmental conditions, e.g., temperature and water conditions, as the peat accumulation process can be easily interrupted by such changes. It is important to understand how immature peatlands develop, what conditions are beneficial to this process, and the present status of these important peatlands. Plant macrofossil analysis and geochemical characteristics of peat were used to determine the plant succession and the degree of decomposition at two peatlands developing in the Changbai Mountain region of northeastern China. The results show that during the entire plant community succession, plants in the two studied peatlands are mainly characterized by sedges (Cyperaceae) and mosses (mainly Sphagnum). Plant macrofossil analysis reveals a wetter trend in the Yuan Lake peatland in the most upper part of peat layer, which provides favorable conditions for peat accumulation and peatland development. Peat geochemical indices indicate a steady decomposition process during initial peatland formation and relative richness in N and P. Plant composition affects peat quality and decomposition and plant communities reflect variations in moisture. Fire events have great impacts on biogeochemical processes, potentially affecting plant succession and promoting peat decomposition. An increase in major and trace elements suggests only weak disturbance due to the considerable distance to human settlements. This study determines the characteristics of pristine mountainous peatlands and highlights the importance of understanding the regular plant community in the early stage of peatland formation, as well as its potential effects on C sinks.

Northeast China contains the greatest concentrations of mountain peatlands in China, occupying about 6.9% of the national peatland resources, with the majority of these located in the mountainous areas to the north. Most of these are in the permafrost zone south of the Russian boarder. Since the 1970s, there has been a more than 35% loss of permafrost in northeast China and the southern border of permafrost has moved northward 50~120 km in response to regional warming. The projected temperature increases in the coming decades will reduce permafrost area by an additional 28-50%. Understanding the impact of temperature change and permafrost degradation on greenhouse gas emission of peatlands is of critical concern for regional and national carbon assessments. In this study we conducted growing season measurement of whole ecosystem CH₄ fluxes from a permafrost peatland located in the Da Xing’anling Mountains, northeast China. The objectives were to quantify CH₄ fluxes, investigate seasonal trends in the flux and determine the dominant environmental and biophysical drivers of the CH₄ flux for the permafrost peatland. CH₄ fluxes at the peatland had an obvious seasonal trend peaking in the late of the growing season. Maximum instantaneous fluxes were 1.34 g CH₄ m^-2 s^-1 and total seasonal CH₄ emissions were 0.38 to 1.27 g C-CH₄ m^-2. We used path analysis to examine environmental and biophysical drivers of the flux and found that soil temperature and thaw depth were most strongly correlated with seasonal CH₄ variability. Our results suggest that soil warming and deepening of the active layer will increase CH₄ emission.

Nitrous oxide (N₂O) is a potent greenhouse gas and peatland is one of the important sources for N₂O emissions due to its abundant carbon and nitrogen reservoir and unique redox environment. Accurate assessments and modeling of N₂O emissions from peatland are thus important but have remained elusive. A major reason is the high temporal and spatial variability in N₂O emission rates. "Hotspots" are temporally and spatially variable micro-sites in peatland that at a given point in time might be responsible for the majority of N₂O emission. Occurrence of a hotspot in peatland requires an optimal set of physical, chemical and biological conditions. However, these conditions are largely unknown. Extremely high temporal variability in hotspot occurrence, often referred to as "hot moments", makes their identification even more difficult. This study monitored the kinetics of N₂O emission in hotspot and tried to answer the following questions 1) what physical and chemical conditions are needed for a N₂O hotspot to emerge, 2) what microorganisms need to enable the hotspot's functioning. The results showed that N₂O emission in hotspot increased with decreasing pH, increasing temperature and porosity. Thaumarchaeota and Proteobacteria seemed to be responsible for the majority of N₂O emission. These results improve our understanding on the mechanism of N₂O emission in hotspot, and are useful in assessments and predictions of N₂O emissions in peatlands.