Inter-Annual Variability of Area-Scaled Gaseous Carbon Emissions from Wetland Soils in the Liaohe Delta, China

Abstract

<div><p>Global management of wetlands to suppress greenhouse gas (GHG) emissions, facilitate carbon (C) sequestration, and reduce atmospheric CO₂ concentrations while simultaneously promoting agricultural gains is paramount. However, studies that relate variability in CO₂ and CH₄ emissions at large spatial scales are limited. We investigated three-year emissions of soil CO₂ and CH₄ from the primary wetland types of the Liaohe Delta, China, by focusing on a total wetland area of 3287 km². One percent is <i>Suaeda salsa</i>, 24% is <i>Phragmites australis</i>, and 75% is rice. While <i>S</i>. <i>salsa</i> wetlands are under somewhat natural tidal influence, <i>P</i>. <i>australis</i> and rice are managed hydrologically for paper and food, respectively. Total C emissions from CO₂ and CH₄ from these wetland soils were 2.9 Tg C/year, ranging from 2.5 to 3.3 Tg C/year depending on the year assessed. Primary emissions were from CO₂ (~98%). Photosynthetic uptake of CO₂ would mitigate most of the soil CO₂ emissions, but CH₄ emissions would persist. Overall, CH₄ fluxes were high when soil temperatures were >18°C and pore water salinity <18 PSU. CH₄ emissions from rice habitat alone in the Liaohe Delta represent 0.2% of CH₄ carbon emissions globally from rice. With such a large area and interannual sensitivity in soil GHG fluxes, management practices in the Delta and similar wetlands around the world have the potential not only to influence local C budgeting, but also to influence global biogeochemical cycling.</p></div