Automated system for measuring ecosystem gas fluxes in tropical forests

Though the Amazon basin várzea forests have been estimated to emit more methane from the stems of their trees than all Arctic wetlands combined, integrated study of the controls, budget and seasonal dynamics of methane cycling in these great forests is lacking. Due to severe seasonal flooding, obtaining continuous gas-flux measurements has proven difficult, incentivizing the need for a continuous, automated system. The team designed, constructed and tested a system in the rainforest of Biosphere 2.

The system consists of two towers: one tower analyzes soil-water surface interfaces and the other measures tree-surface interfaces. This provides year-round monitoring and withstands up to 10 feet of flooding. Polyurethane foam in the towers floats along installed guide rails during floods for sensor measurements at three heights along a tree.

Each tower contains a chamber which is sealed against a surface by an actuator controlled by pressure sensors. Gas enclosed within the chamber is then pumped to a trace gas analyzer where concentrations of methane, carbon dioxide and water vapor are measured. The system is controlled by a master hub and a user controller which transmit data via radio transmission. The interconnected system allows researchers to take gas flux measurements 12 times a day at multiple locations year-round in rainforest environments.