A Comprehensive Framework for Modeling Emissions from Tropical Soils and Wetlands

Lead Investigator: 
Melanie Mayes
Participating Staff: 
Yang Song, Qiuming Yao, Ryan Quinn, Jana Randolph Phillips, Abishek Biswas
Chongle Pan (ORNL), Terry Hazen (ORNL), Whendee Silver (UC Berkeley)
Climate and Environmental Sciences Division, U.S. DOE Office of Biological and Environmental Research.
Start Date: 
End Date: 


Project Description

Tropical wetlands and wetlands soils account for over 2/3 of the global wetland methane (CH4) emissions. Tropical wetlands are also important contributors to other greenhouse gases such as carbon dioxide (CO2) and nitrous oxide (N2O). Gas emissions in soils and wetlands are complicated and are affected by fluctuations in water levels and oxygen (O2) availability. Most models lack the ability to transition between these conditions, and therefore the ability to predict gas emissions. Further, emissions are strongly affected by soil microbes and available sources of energy, such as nutrients and minerals. The objective of this project is to develop a modeling framework that represents microbial functions, mineral interactions and nutrient supply, and water and oxygen content. Fieldwork will be conducted along transects from valleys to ridgetops in a wet tropical forest in Puerto Rico, and at a peat bog in Panama. Long-term, continuous measurements of CO2, CH4, and N2O from soils will be made at each site. Lab experiments will measure emissions of CO2, CH4, H2, H2S, and O2 from soils under specific water content, terminal electron acceptor additions, and oxygen concentrations. Microbial functions (or traits) will be identified using advanced genomic techniques, as well as by measuring enzymes and proteins. The influence of soil minerals and nutrient status will also be measured. Variation in gas emissions will be related to microbial traits, water and oxygen content, and soil characteristics at each field location using modeling.

A conceptual model describing the multi--‐scale experimental and modeling project “A Comprehensive Framework for Modeling Emissions from Tropical Soils and Wetlands”. The project will measure soil respiration in tropical wetlands and wet soils, and will link the type of gases released (CO2, N2O, CH4) to soil moisture, oxygen content, and the soil microbiome. A detailed small--‐scale model will encompass the transition from aerobic to anaerobic soils, and a simplified model will be developed for larger scales and longer timeframes. Finally, the project will build an improved map of tropical wetlands and wet soils for model application at the large scale.

This model will be rich in details and it will be appropriate for spatial scales ranging from millimeters to decimeters. A simplified modeling approach will also be developed for applications from meters to kilometers. Finally, information about the exact locations and extent of tropical wetlands is lacking, so data from the remote sensing approaches will be used to improve existing inventories of tropical wetlands. This project relates microbial traits, soil characteristics, soil water content, and soil oxygen concentrations, and uses the information to builds models to improve predictions of soil gas emissions in wet tropical soils and wetlands.