Are tropical uplands regional hotspots for methane and nitrous oxide?

Lead Research Organisation: University of Aberdeen
Department Name: Inst of Biological and Environmental Sci


Tropical ecosystems are major sources of the greenhouse gases (GHGs) methane (CH4) and nitrous oxide (N2O), which are 25 and 298 times more effective than carbon dioxide (CO2), respectively, in trapping long-wave radiation in the atmosphere. Increases in CH4 and N2O concentrations since the start of the Industrial Revolution are responsible for over one-third of global warming, and future changes in the atmospheric budgets of these GHGs have implications for the Earth's climate and environmental conditions. N2O emissions, in particular, are projected to rise in the future due to agricultural expansion and enhanced atmospheric nitrogen deposition. Recent studies of the global budgets of CH4 and N2O using satellite imagery, atmospheric measurements, and modelling suggest that significantly more CH4 and N2O are released from the tropics than previously thought due to unaccounted sources of CH4 and N2O. It is critical for us to identify and characterise these 'missing' sources if we wish to understand the current contribution of the tropics to GHG budgets. Knowledge of these 'missing' sources is also necessary for predicting how tropical GHG emissions are likely to respond to future environmental or climatic change. One strong potential candidate for these 'missing' sources of CH4 and N2O are tropical uplands. Tropical uplands have been conspicuously absent from existing atmospheric budgets, because scientific attention has largely focused on CH4 and N2O emissions from lowland forests, savannas, or wetlands. Studies from tropical uplands suggest that they are potentially large sources of CH4 and N2O, with emissions that are equal to or greater than those from lowland environments. Upland rainforests in Puerto Rico, for example, emit more CH4 than lowland forests, with emission rates that are on par with northern wetlands, the largest natural sources of CH4 worldwide. To address these gaps in knowledge, we will conduct a comprehensive study of CH4 and N2O cycling in the Peruvian Andes, using a mixture of field measurements, controlled environment studies, and mathematical modelling. Specifically, we will: 1. Investigate how CH4 and N2O fluxes vary in space and time along an environmental gradient that spans 3000 m of altitude, from lowland rainforest to upper montane rainforest. 2. Explore how key environmental variables (e.g., plant productivity, climate, soil moisture, carbon and nitrogen availability, oxygen) influence CH4 and N2O emissions. 3. Determine if existing mathematical models are able to simulate CH4 and N2O emissions from tropical ecosystems, adapting these models as necessary to better simulate field observations. 4. Determine if GHG emissions from the Andes are able to account for some of the 'missing' tropical sources of CH4 and N2O by extrapolating our field observations to the regional scale using a combination of mathematical modelling, satellite imagery, and land cover databases (i.e., GIS). The proposed research will greatly advance our understanding of CH4 and N2O emissions for an important but understudied region, and will help us determine the relative contribution of Andean ecosystems to the CH4 and N2O budgets for South America. Knowledge of the emission rates and environmental controls on CH4 and N2O fluxes from upland Andean ecosystems will also help us evaluate whether other tropical uplands are likely to be sources of CH4 and N2O, and assess their potential contributions to the global atmospheric budgets of CH4 and N2O. Lastly, the development and adaptation of mathematical models that accurately simulate tropical CH4 and N2O fluxes will allow us to predict the likely response of tropical uplands to future environmental or climatic change.


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Description Methane emissions differed significantly across the ecotypes across the transect. See lead RO report
Exploitation Route Data could be used by others for modelling / upscaling
Sectors Environment

Description Tropical uplands are a potentially large and important source of two important greenhouse gases, methane (CH4) and nitrous oxide (N2O) often overlooked by past empirical and modelling studies. We show that tropical uplands can act either as sources or sinks for methane, but act as a source of nitrous oxide.
Sector Environment
Impact Types Societal

Title Soil and gas measurements from Puna grasslands under different land management over one year 
Description The dataset contains concentrations of total soil organic carbon, soil carbon fractions, soil CO2 fluxes, soil temperature and moisture in the Peruvian Andes. Measurements and sampling took place between 2010 and 2013. Data were generated as part of a larger NERC project: 'Are tropical uplands regional hotspots for methane and nitrous oxide' 
Type Of Material Database/Collection of data 
Year Produced 2017 
Provided To Others? Yes