Carbon dioxide and methane fluxes in the growing and non-growing season in the Dajiuhu subtropical peatland: A five-year measurement using the eddy covariance technique

Abstract

Peatlands present substantial terrestrial carbon reservoirs actively engaged in land-atmosphere carbon exchanges. Ongoing variations in carbon dynamics, attributed to global climate change, underscore the necessity of elucidating the connections between carbon fluxes and meteorological parameters. Limited studies have delved into disparities in carbon fluxes and the mechanisms mediating them during growing and non-growing seasons on a long-term scale, particularly in subtropical peatlands. Consequently, this study utilized the eddy covariance technique in the Dajiuhu peatland to investigate five-year CH4 and CO2 fluxes, longside meteorological characteristics. The Dajiuhu peatland functioned as a CO2 sink and CH4 source, ultimately serving as a carbon sink. A substantial portion of the annual fluxes was measured during the non-growing season, with elevated CO2 uptake and CH4 emission during the growing season. Further analyses revealed that photosynthetically active radiation (PAR), soil temperature (Ts), air temperature (Ta), and soil water content (SWC) were critical environmental parameters influencing fluctuations in CO2 and CH4 fluxes. Two distinct controlling pathways for CO2 fluxes were identified. In the growing season, PAR emerged as the most influential factor in CO2 flux variations, and increasing Ts weakened CO2 absorption by decreasing SWC. During the non-growing season, Ts emerged as the most influential factor in CO2 exchanges, with lower Ts leading to decreased CO2 uptake. Additionally, CH4 flux variations were significantly regulated by PAR and Ts in both periods. The results illustrated that vascular plants played a pivotal role in the dynamics of carbon between peatlands and the atmosphere. Furthermore, it was discovered that the Dajiuhu peatland contributed to mitigating global warming in both the short and long term, with SGWP identified as a more reliable evaluation index. Our findings underscore the essential ecological function of the Dajiuhu subtropical peatland and provide a theoretical foundation for scientifically managing carbon in natural subtropical peatlands.