Methane emission from natural wetlands: interplay between emergent macrophytes and soil microbial processes. A mini-review

Abstract

The role of the nitrogen cycle in repression of methane production is probably low. In contrast to wetlands particularly created for the purification of nitrogen-rich waste waters, concentrations of inorganic nitrogen compounds are low in the root zones in the growing season due to the nitrogen-consuming behaviour of the plant. Therefore, nitrate hardly competes with other electron acceptors for reduced organic compounds, and repression of methane oxidation by the presence of higher levels of ammonium will not be the case. The role of the iron cycle is likely to be important with respect to the repression of methane production and oxidation. Iron-reducing and iron-oxidizing bacteria are ubiquitous in the rhizosphere of wetland plants. The cycling of iron will be largely dependent on the size of the oxygen release in the root zone, which is likely to be different between different wetland plant species. The role of the sulfur cycle in repression of methane production is important in marine, sulfate-rich ecosystems, but might also play a role in freshwater systems where sufficient sulfate is available. Sulfate-reducing bacteria are omnipresent in freshwater ecosystems, but do not always react immediately to the supply of fresh sulfate. Hence, their role in the repression of methanogenesis is still to be proven in freshwater marshes.

The role played by aquatic macrophytes regarding CO2 balance in a tropical coastal lagoon (Cabiúnas Lagoon, Macaé, RJ)

“…Aquatic plant roots influence the activity of microorganisms through organic matter production and oxygen transportation to the rhizosphere (Garnet et al 2005). On the other hand, methane found in the sediment can be transported to the atmosphere across the macrophytes' aerenchyma tissues (Laanbroek, 2010), reducing gas consumption and carbon accumulation in the sediment. Although the amount of methane emitted into the atmosphere is just a relatively small proportion of the total C accumulated in the sediment, it can be significant in terms of global warming due to the atmosphere.…”

“…Concerning the CO 2 dynamics in coastal aquatic ecosystems, studies performed at the same system showed that it tends to be a consistent CO 2 source to the atmosphere (Marotta et al, 2009;2010). However, these studies did not evaluate the role of aquatic macrophytes gas transportation and alterations in the littoral zone to CO 2 dynamics.…”

“…It has been shown that macrophytes significantly influence trace gas exchange due to their influence over C production, consumption and transport processes (Nobel, 1983;Laanbroek, 2010). Gas…”

Plant-mediated methane and nitrous oxide fluxes from a carex meadow in Poyang Lake during drawdown periods

“…CH 4 and N 2 O emissions from wetlands are subjected to a number of biotic and abiotic controls Bridgham et al 2013), among which plants are considered to be the major one because they can strongly affect CH 4 and N 2 O production, consumption, and transportation (Rückauf et al 2004;Laanbroek 2010). Plant presence can increase soil CH 4 flux by enhancing substrate availability.…”

“…In addition, plants can supply microbes with labile substrates and serve as a transport pathway, which may increase N 2 O emissions (Rückauf et al 2004;. Previous studies have reported increases (Bellisario et al 1999;Laanbroek 2010) or decreases (Kao-kniffin et al 2010;Sutton-Grier and Megonigal 2011) of CH 4 emission in response to an increase in plant biomass or productivity. The contribution of plant-mediated CH 4 flux varied substantially among species and wetland types (Whiting and Chanton 1992;Ding et al 2005;Dorodnikov et al 2011).…”