Plant controls over tropical wetland nitrous oxide dynamics: a review

Tropical wetlands are an important global source of greenhouse gas emissions, including nitrous oxide, a potent and long-lasting greenhouse gas. Tropical wetland ecosystems can be highly heterogeneous, featuring a variety of vegetation types, from grasses through to palms and mangroves. While soil conditions (particularly soil moisture and pH) are essential for determining the formation of nitrous oxide in soils, plants have a central role in determining the balance of emissions. In this review, we summarise the importance of vegetation in regulating tropical wetland nitrous oxide dynamics. We show how a variety of plant-mediated processes can exert key controls over wetland plant-soil nitrogen transportation and transformations. Key mechanisms of plant regulation of dynamics include influencing substrate availability (carbon and nitrogen) through litter inputs, rhizodeposition, root turnover and plant nitrogen uptake, rhizosphere biology, and plant-mediated nitrous oxide transportation, all of which can vary between species and dominant vegetation types. We propose that there is a critical need to better quantify such processes across dominant wetland ecotypes, to support improved upscaling of emissions, and assess their sensitivity to future environmental change.