Abstract
Plants are a major factor influencing methane emissions from wetlands, along with environmental parameters such as water table, temperature, pH, nutrients and soil carbon substrate. We conducted a field experiment to study how different plant species influence methane emissions from a wetland in Switzerland. The top 0.5 m of soil at this site had been removed five years earlier, leaving a substrate with very low methanogenic activity. We found a sixfold difference among plant species in their effect on methane emission rates: Molinia caerulea and Lysimachia vulgaris caused low emission rates, whereas Senecio paludosus, Carex flava, Juncus effusus and Typha latifolia caused relatively high rates. Centaurea jacea, Iris sibirica, and Carex davalliana caused intermediate rates. However, we found no effect of either plant biomass or plant functional groups – based on life form or productivity of the habitat – upon methane emission. Emissions were much lower than those usually reported in temperate wetlands, which we attribute to reduced concentrations of labile carbon following topsoil removal. Thus, unlike most wetland sites, methane production in this site was probably fuelled chiefly by root exudation from living plants and from root decay. We conclude that in most wetlands, where concentrations of labile carbon are much higher, these sources account for only a small proportion of the methane emitted. Our study confirms that plant species composition does influence methane emission from wetlands, and should be considered when developing measures to mitigate the greenhouse gas emissions.
Highlights
Wetlands are the largest natural source of the important greenhouse gas methane (CH4), contributing about one-third (80–110Tg yr21) to global emissions [1,2,3]
Methane emissions were sensitive to changes in air temperature, but this did not affect the comparison among different plant species since the replicates within species were spread over different days and temperatures
Methane emissions from natural wetlands have been reported to range between 0 and 660 mg m22 day21 [1,2,30,35]. They varied from 0.25 to 1.55 mg m22 hr21, which is lower by a magnitude of thousands than those measured at many other temperate wetlands [27,36]
Summary
Wetlands are the largest natural source of the important greenhouse gas methane (CH4), contributing about one-third (80–110Tg yr21) to global emissions [1,2,3] This methane is produced under anoxic conditions by methanogenic microbes (Archaea) [4]. The amounts emitted from a wetland soil can be significantly influenced by vascular plants [5,6,7,8], through their effects upon the production, transport and consumption of methane in soils [4,9,10] These processes vary greatly among plant species, and their net impact upon methane emissions can range from negative to positive [5,10,11,12]. To better understand why plant species influence methane emissions differently, comparative studies are needed in wetland ecosystems under homogeneous field conditions
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