## 1 Introduction  
According to the IPCC 'Special Report on Global Warming of 1.5 \({}^{\circ}\)C', human-induced global warming has reached 0.87 \({}^{\circ}\)C since the Industrial Revolution, and it is estimated to reach 1.5 \({}^{\circ}\)C in the period 2030-2052 [1]. The global average temperature increased by 0.9 \({}^{\circ}\)C during 2011-2015 compared with that in 1750, and the average temperature increased by 0.2 \({}^{\circ}\)C during 2015-2019 compared with that during 2011-2015 [2]. The rise in surface temperature induced by global warming is the most prominent in northern high latitudes [3]. Temperatures in northern latitudes are currently increasing at a rate of 0.6 \({}^{\circ}\)C/10 yr, which is two times higher than the global average [4]. In particular, Northeast China exhibits the largest warming trend, with an increase rate of 0.36 \({}^{\circ}\)C/10 yr [5]. Climate change is usually regarded as the most important driver of global soil carbon (C) stocks [6, 7]. One of the most prominent aspects of climate change is global warming, which is mainly driven by the increase in greenhouse gas (GHG) concentrations in the atmosphere [8, 9]. To maintain global warming below 2 \({}^{\circ}\)C, GHG emissions have to be drastically reduced. Despite covering only 3% of the global land area, northern peatlands have accumulated large C stocks [10]. According to statistics, one-third (455 PgC) of the global soil C is stored in northern peatlands, which play a critical role in C cycles on the global scale [11]. The balance between soil C storage and loss will drive powerful carbon-climate feedback over the coming century. The representation of soil C cycling (both conceptually and numerically) has critical implications on the prediction of the response of peatlands to environmental change and anthropogenic forcing. For example,the response of peatlands to warming represents a critical source of uncertainty in efforts toward projecting carbon-climate feedbacks over the upcoming century [12]. Permafrost refers to ground that remains frozen for two or more consecutive years and underlies many Arctic and boreal ecosystems. In the current terrestrial ecosystem, permafrost represents the largest soil carbon pool at 1330-1580 Pg [13; 14; 15], which is significantly higher than the C content in vegetation (650 Pg) and almost twice that in the atmosphere (730 Pg) [16; 17]. Moreover, soil C storage in permafrost regions accounts for more than 50% of the global soil carbon [18]. However, permafrost in high latitudes and high altitudes is highly sensitive to climate change, and the growth rate of temperature in these regions in the past 30 years has been twice the global growth rate [19]. Permafrost temperature has increased by 0.29 \(\pm\) 0.12 \({}^{\circ}\)C between 2007 and 2016 on the global scale [20]. Permafrost and peatlands are interdependent in Northeast China. Under the unique cold, stagnant, and anaerobic environment of peatlands in permafrost regions [21], a large amount of C is stored in the soil. In peatlands, deeper water tables favor CO\({}_{2}\) and N\({}_{2}\)O emissions and shallower water tables favor CH\({}_{4}\) emissions [22; 23]. As a result, these regions are more vulnerable to climate change and likely to release more GHGs in response to climate warming. Specifically, clarifying the carbon exchange process and emission characteristics of the peatland in the Great Hing'an Mountains in northern China is of great significance for reducing GHG emissions and controlling climate warming [24]. Vegetation plays a crucial role in carbon cycling and the thermal state of permafrost [25; 26]. Climate warming generally leads to changes in vegetation composition and structure [27; 28]. In recent decades, most boreal peatlands across the world have experienced substantial changes in vegetation composition and structure as a consequence of climate warming [27; 28]. Field observations have consistently indicated that the expansion of shrubs and forbs has been changing pan-Arctic vegetation landscapes [29; 30].