# Characteristics of Carbon Fluxes and Their Environmental Control in Chenhu Wetland, China
## 1 Introduction  
Wetlands, as one of the most significant carbon reservoirs within terrestrial ecosystems, play a crucial role in the global carbon cycle. Despite occupying merely 6% of the Earth's land area, wetlands are responsible for sequestering approximately 20% to 30% of the total soil carbon globally. Their functionality is essential for stabilizing the global climate and mitigating the impacts of the greenhouse effect [1, 2]. In recent years, climate change and anthropogenic activities have resulted in substantial reductions in wetland areas and alterations in land use patterns [3], as well as significant changes in the natural carbon cycling processes within ecosystems [4]. The classification of wetlands as either carbon sources or carbon sinks serves as a critical metric for evaluating the effectiveness of wetland ecological restoration efforts and the capacity of these ecosystems to contribute to climate change mitigation [5]. However, considerable uncertainties persist regarding the carbon and water budgets of wetland ecosystems due to a multitude of individual and interactive factors, including geographical location, vegetation types, soil conditions, meteorological factors, and human activities [6]. For example, the alpine wetland ecosystem of Qinghai Lake consistently functions as a \"carbon sink\" throughout the year, while the peatland atYikulanwa Station, located south of Qinghai Lake, is characterized as a \"carbon source\" [2; 7]. Therefore, it is imperative to investigate and analyze the carbon exchange characteristics and carbon budget mechanisms of wetland ecosystems across various regions and types. Monitoring carbon flux within these ecosystems is a critical method for determining whether they function as carbon sources or sinks, and it is also a vital component in understanding the carbon cycle within terrestrial ecosystems [7]. The middle reaches of the Yangtze River constitute a significant region characterized by the presence of lake and reservoir wetlands. This area exhibits the highest density of wetlands recognized as important at both international and national levels in China [8]. Furthermore, it is one of the regions in China that demonstrates heightened sensitivity to extreme rainfall as a consequence of climate change [9]. In recent years, the region has experienced a notable increase in temperature, accompanied by an uneven distribution of precipitation, a marked reduction in wetland area, and the deterioration of wetland ecological functions [10]. These alterations affect the biophysical and chemical processes within wetlands, thereby influencing the carbon cycle both in the middle Yangtze reaches and on a global scale. Currently, domestic researchers have undertaken investigations into carbon flux within various wetland ecosystems, including alpine wetlands [7; 11], arid desert wetlands [12; 13; 14], estuary delta wetlands, coastal wetlands [5; 15; 16; 17], the Sanjiang Plain swamp wetland [18], the Shennongjia subalpine wetland [19], and constructed wetlands [20]. However, while some studies have focused on carbon flux in wetland ecosystems along the middle reaches of the Yangtze River, the majority of these investigations have primarily concentrated on lake wetlands, such as those found located in Hongge Lake [21], Taihu Lake [22], Poyang Lake [23], and Dongting Lake [24]. Marsh wetlands constitute a significant component of the wetland ecosystem in the middle Yangtze reaches, possessing considerable ecological value and playing a crucial role in sustaining the environmental functions of these wetlands. Nevertheless, there is a notable lack of direct measurements concerning carbon exchange between the atmosphere and the marsh wetland ecosystem, resulting in limited evidence to elucidate the dynamics of carbon exchange and its relationship with environmental controls within this ecosystem.