Abstract
Understanding the functional relationship between greenhouse gas fluxes and environmental variables is crucial for predicting the impacts of wetlands on future climate change in response to various perturbations. We examined the relationships between methane (CH4) emission and temperature in two marsh stands dominated by the Phragmites australis and Cyperus malaccensis, respectively, in a subtropical estuarine wetland in southeast China based on three years of measurement data (2007–2009). We found that the Q 10 coefficient of CH4 emission to soil temperature (Q s10) from the two marsh stands varied slightly over the three years (P > 0.05), with a mean value of 3.38 ± 0.46 and 3.89 ± 0.41 for the P. australis and C. malaccensis stands, respectively. On the other hand, the three-year mean Q a10 values (Q 10 coefficients of CH4 emission to air temperature) were 3.39 ± 0.59 and 4.68 ± 1.10 for the P. australis and C. malaccensis stands, respectively, with a significantly higher Q a10 value for the C. malaccensis stand in 2008 (P < 0.05). The seasonal variations of Q 10 (Q s10 and Q a10) differed among years, with generally higher values in the cold months than those in the warm months in 2007 and 2009. We found that the Q s10 values of both stands were negatively correlated with soil conductivity, but did not obtain any conclusive results about the difference in Q 10 of CH4 emission between the two tidal stages (before flooding and after ebbing). There were no significant differences in both Q s10 and Q a10 values of CH4 emission between the P. australis stand and the C. malaccensis stands (P > 0.05). Our results show that the Q 10 values of CH4 emission in this estuarine marsh are highly variable across space and time. Given that the overall CH4 flux is governed by a suite of environmental factors, the Q 10 values derived from field measurements should only be considered as a semi-empirical parameter for simulating CH4 emissions.
Highlights
Methane is a greenhouse gas that is 34 times more potent than carbon dioxide on a 100-year time scale and plays an important role in global climate change [1]
Except in 2009, the percentage variance in CH4 emission explained by air or soil temperature was greater for the C. malaccensis stand compared to the P. australis counterpart (Fig 3)
In 2007, we found significantly lower Qs10 and Qa10 of CH4 emission from the P. australis stand before flooding (BF) compared to those after ebbing (AE) (P < 0.05), while for the C. malaccensis stand, the difference was not statistically significant between the two tidal stages (P > 0.05)
Summary
Methane is a greenhouse gas that is 34 times more potent than carbon dioxide on a 100-year time scale and plays an important role in global climate change [1]. It is essential to develop a thorough understanding of the relationships between various environmental factors and CH4 emissions from estuarine wetlands in order to accurately predict the impacts of natural and anthropogenic perturbations on CH4 release, as well develop appropriate management strategies to minimize the potential adverse climatic impacts of wetlands. Temperature is in general a major factor governing wetland CH4 emission to the atmosphere [6, 11, 12], some researchers have reported a weak correlation between CH4 emission and temperature [13, 14]. Few studies far have reported on the Q10 of wetland CH4 emission [6, 20, 21]
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