Influence of Elevated CO2 on Transpiration


We erected two 3-meter diameter chambers in the C 3 community in order to determine whether reductions in transpiration would influence the water table depth, and thus hydrologic export. Each chamber was fitted with three of piezometer well nests, with wells at 30 cm and 75 cm depth. A pressure transducer measured the difference in water height between the two wells at 5-minute intervals continuously. The system was sensitive enough to detect the influence of changes in water table depth on hydraulic head in the upper profile of the marsh .

Changes in the average difference in water pressure
between shallow and deep piezometer wells.

A series of trials were run to determine if elevated CO could influence water table depth. At the start of each trial, one chamber was treated with ambient CO2 and the other with 2X-ambient CO2 . After periods of time that ranged from 6 hours to 7 days, the ambient and elevated CO treatments were switched. We did not observe an influence of switching the CO2 treatment on water table depth in any trials, and concluded that the influence of transpiration is less than our estimated sensitivity of a 1-cm change in water table depth.


Research Questions