Dr. Catherine Potvin

This is a question that we set out to answer by establishing two eddy covariance flux towers one in a grazed pasture and one embedded in a plantation. Specifically, we are asking: How does the transition in land use from grazed pasture to tree plantation affect ecosystem fluxes of C? We hypothesize that the plantation will be a large sink for CO₂ while the pasture may be a smaller sink, or a small source.

To test this hypothesis we have to estimate the C fluxes and stocks for both land use types. NEE measurements are done with two paired eddy covariance systems, one located in the grazed pasture and one in the experimental plantation.

The eddy covariance system uses a Campbell three axis sonic anemometer and a LI-COR 7500 open path infra red sensor to monitor CO₂ and water vapor exchange. The measurements are made at 3 m above the canopy height, at a frequency of 20 Hz and the data will be processed on site every half-hour.

In February 2007, the Sardinilla plantation tower was raised 15 m above ground, giving it a clearance above the vegetation of about 4-6 m. Researchers from ETH, Zurich, took over operations of both the plantation and the pasture towers. The figure below is an example of CO₂ and water flow above the plantation during the dry season.