Abstract
Littoral wetlands are globally important for sustainable development; however, they have recently been identified as critical hotspots of nitrous oxide (N2O) emissions. N2O flux from subtropical littoral wetlands remains unclear, especially under the current global warming environment. In the littoral zone of Lake Poyang, a simulated warming experiment was conducted to investigate N2O flux. Open-top chambers were used to raise temperature, and the static chamber-gas chromatograph method was used to measure N2O flux. Results showed that the littoral zone of Lake Poyang was an N2O source, with an average flux rate of 8.9 μg N2O m−2 h−1. Warming significantly increased N2O emission (13.8 μg N2O m−2 h−1 under warming treatment) by 54% compared to the control treatment. N2O flux in the spring growing season was also significantly higher than that of the autumn growing season. In addition, temperature was not significantly related to N2O flux, while soil moisture only explained about 7% of N2O variation. These results imply that N2O emission experiences positive feedback effect on the ongoing warming of the climate, and abiotic factors (e.g., soil temperature and soil moisture) were not main controls on N2O variation in this littoral wetland.
Highlights
The global temperature has increased by 0.85 ◦C over the past three decades and is projected to increase by 0.3–4.8 ◦C by the end of the 21st century [1]
According to the analysis results of the linear mixed-effects model, we found that warming had a significant effect on N2O flux, as did the sampling date (Table 2)
Consistent with previous results in other wetlands [2,15], we found that warming significantly increased N2O flux in this littoral wetland during the uninundated period
Summary
The global temperature has increased by 0.85 ◦C over the past three decades and is projected to increase by 0.3–4.8 ◦C by the end of the 21st century [1]. Climate warming may exert great influences on greenhouse gas (GHG) fluxes in wetlands [2,3] due to the large carbon and nitrogen stocks/emissions and the high temperature sensitivity [4,5,6]. Carbon dioxide (CO2) is the most abundant GHG in the atmosphere, the global warming potential of N2O is approximately 265 times higher than that of CO2 over a 100-year timescale [9]. The concentration of atmospheric N2O reached new highs in 2018 at 331 ppb, and natural sources (e.g., wetlands, forests, and oceans) contributed about 60% of global N2O emissions [10]. The global N2O budget is far from being fully understood due to the lack of available data from all natural ecosystems [11], especially in the largely unexplored littoral wetlands
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