EFFECTS OF FACE SYSTEM OPERATION ON THE MICROMETEOROLOGY OF A LOBLOLLY-PINE STAND

The effects of the gas injection operation on air movement in the lobl olly pine stand at the Duke Forest prototype BNL-FACE User Facility we re investigated The micrometeorological conditions were measured using three-dimensional sonic anemometers in the center of the FACE ring at two heights, one just above the canopy (median height of the canopy = 9 m) at 11.6 m and another at 6.8 m above the ground where the canopy war the most dense. While the micrometeorological parameters were sam pled continuously at 10 Hz, the gas injection system was turned altern atively on and off every 5 min for about 100 h. The analyses indicated that the system operation had little effect on the micrometeorology p rocesses above the canopy. There were small magnitude but detectable c hanges in some of the micrometeorological parameters within the canopy , primarily during stable atmospheric conditions, in response to this 5-min alternation. The gas injection operation created a slightly dive rging windfield in the top half of the canopy in the enclosed stand A slight dampening of the vertical wind and air temperature fluctuations was detected No detectable effects on the mean, or accumulated, heat and momentum fluxes at the measurement locations were found. in genera l, the system was shown to cause minimal disturbances to the natural e nvironment compared to traditional carbon dioxide (CO2) enrichment fac ilities and it provides a better alternative for long-term ecological studies.