# Characteristics of Carbon Fluxes and Their Environmental Control in Chenhu Wetland, China
## 3 Results and Discussion
### Dynamics of CO\({}_{2}\) Flux over Various Temporal Scales
#### 3.2.2 Seasonal Variations in NEE
However, it is slightly lower than the CO\({}_{2}\) absorption rates recorded for Taiwan Lake (25.25 molCO\({}_{2}\cdot\)m\({}^{-2}\)) [37], Poyang Lake (28.29 molCO\({}_{2}\cdot\)m\({}^{-2}\)) [38], and Dongting Lake (33.36 molCO\({}_{2}\cdot\)m\({}^{-2}\)) [24]. Furthermore, the CO\({}_{2}\) absorption capacity of the Chenhu wetland is significantly less than that of Yunxiao (Zhangjiangkou mangrove wetland) (45.66 molCO\({}_{2}\cdot\)m\({}^{-2}\)) [39], Hongze Lake (49.53 molCO\({}_{2}\cdot\)m\({}^{-2}\)) [40], the eastern Chong  
Figure 4: The daily variation of NEE on an annual basis (**a**) and the seasonal variation of monthly total NEE (**b**) for the Chenhu wetland during the year 2022.  
ming tidal flat (53.58 molCO\({}_{2}\cdot\)m\({}^{-2}\)) [41; 42; 43], and Gaoqiao (Zhanjiang mangrove wetland) (61.48 molCO\({}_{2}\cdot\)m\({}^{-2}\)) [44]. The observed variation in carbon sequestration capacity among subtropical wetland ecosystems can be attributed to differences in meteorological and hydrological conditions across different years, as well as the distinct vegetation compositions present in various wetlands [45]. For example, mangroves serve as the predominant plant species in the flux towers in the Zhangjiangkou and Zhanjiang mangrove wetlands, whereas poplar plantations represent the primary vegetation in the flux tower at Hongze Lake. In contrast, the vegetation surrounding the flux tower at the eastern Chongming tidal flat is predominantly composed of a mixed community of reeds and _Spartina alterniflora_. The substantial aboveground biomass present in these wetlands significantly contributes to CO\({}_{2}\) flux [46]. \begin{table}
\begin{tabular}{p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt}} \hline \hline
**Study Site** & **Longitude/Latitude** & **Wetland Type** & **Dominant Plant Species** & **Measuring Year** & **Annual NEE** & **References** \\ \hline Yunxiao wetland & 23.9240\({}^{\circ}\) N, 117.4147\({}^{\circ}\) E & Estuarine mangrove wetland & _Kandelia obovata_, _Avicemnia marina_, _Aigericas corriculatum_ & 2019–2020 & 45.66 & [39] \\ \hline Dongting Lake & 29.4875\({}^{\circ}\) N, 113.0525\({}^{\circ}\) E & Lake wetland & _Miscanthus sacchariflorus_ & 2014–2016 & 33.36 & [24] \\ \hline Eastern Chongming tidal flat & 31.6333\({}^{\circ}\) N, 121.9667\({}^{\circ}\) E & Coastal wetland & _Phragmites australis_, _Spartina alterniflora_, _Scripus mariqueter_ & 2005–2007, 2012 & 53.58 & [41; 42; 43] \\ \hline Gaoqiao & 21.57\({}^{\circ}\) N, 109.76\({}^{\circ}\) E & Coastal wetland & _Aigericas corriculatum_, _Bruguiera gymnorrhiza_ & 2010 & 61.48 & [44] \\ \hline Chongxi wetland & 31.72\({}^{\circ}\) N, 121.23\({}^{\circ}\) E & Estuarine wetland & _Phragmites australis_ & 2009 & 18.75 & [36] \\ \hline Poyang Lake E–116.5\({}^{\circ}\) E & & & & _Carecinerascens_, _Phalarisarundinacea_, _Miscantthussacchariflorus_, _Phragmites communuis_ & 2013.08–2016.06 & 28.29 & [38] \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Comparison of annual NEE (unit molCO\({}_{2}\cdot\)m\({}^{-2}\)) between Chenhu wetland and other subtropical wetlands in China. Figure 5: Comparison of annual NEE in subtropical wetlands. Research demonstrates that various ecosystems exhibit distinct dynamics regarding carbon sources and sinks, which are influenced by differing vegetation characteristics and environmental conditions. Furthermore, even within the same ecosystem, ecological impacts can vary due to changes in the environment [11]. In 2022, the Northern Hemisphere experienced a significant drought, leading to annual rainfall levels in the Chenhu wetland that were markedly lower than those recorded in previous years. Additionally, both the maximum and minimum temperatures during this period were elevated compared to the same timeframe in the preceding year. To obtain more accurate measurements of carbon flux within the Chenhu wetland ecosystem, it is imperative to implement extended and continuous monitoring efforts.