
Each of the four EcoCELLs is a separate mesocosm designed as an open-flow, mass-balance system for the measurement of trace gas exchange.
Air temperature and humidity, trace gas concentrations, and incoming air flow rate are strictly controlled as well as being accurately and precisely measured. Temperature control is achieved without condensation; humidity is controlled by a combination of regulating the dew point and flow rate of incoming air; wind speed and flow pattern are adjustable. The soil medium in each cell is contained in three 2.7m x 1.8m x 2m (down wind length x w x d) acrylic walled boxes -- lysimeter/rhizotron -- which closely adjoin each other, forming a continuous plant canopy. Each lysimeter/rhizotron is mounted on a set of four load cells capable of discriminating a change in weight of 250 g in a total weight of 20 x 106 g. The weighing lysimeters provide a primary check on the mass-balance gas exchange system's calibration in that the integral of the mass-balanced based measurements of transpiration must equal the weight change of the lysimeter over that period of time. A plant canopy transpiring at an average rate will lose a detectable amount of weight in approximately 20 minutes.

(a) View of EcoCELL #4 lysimeters before adding soil. (b) View of EcoCELL from the basement showing lysimeter load cells. (c) Cross-sectional elevation view of EcoCELL. |