PARENT SESSION
Monday, August 7, 5:00-6:30 pm
Poster Session 4 - Soil, mycorrhizal, and microbial ecology
Exhibit Hall, Ballroom Level, Cook Convention Center

Addressing spatial and temporal variability of soil CO₂ flux using an automated 16-chamber multiplexed system.

Madsen, Rodney¹, Xu, Liukang¹, McDermitt, Dayle^*,1, Burba, George¹, Garcia, Rick¹, Demetriades-Shaw, Tanvir¹, Scoby, David², Arkebauer, Timothy², ¹ LI-COR Biosciences, Lincoln, NE² University of Nebraska, Lincoln, NE

ABSTRACT- High spatial and temporal variability of soil CO₂ flux information is essential to understanding how environmental (soil moisture, rain events, temperature, etc.) and biological (photosynthesis, LAI, etc.) factors regulate soil CO₂ flux. We have developed a 16-port automated multiplexing system. It can cover an area with a radius of 17 m. As we know soil CO₂ flux is driven primarily by the CO₂ diffusion gradient across the soil surface. The flux measurement should be made without affecting the diffusion gradient and without having any chamber induced pressure perturbation. An improperly designed chamber may have the problem of chamber induced pressure perturbation during the measurement under windy conditions, due to the Venturi effect. This could lead to a magnitude high overestimation of the flux. We are presenting a new chamber vent design capable of maintaining pressure equilibrium between the inside and outside of the chamber under both calm and windy conditions. Also, to minimize the impact of decreased CO₂ diffusion gradient on the CO₂ flux measurement, the chamber CO₂ concentration vs. time is fitted with an exponential function. The soil CO₂ flux is estimated by calculating the initial slope from the exponential function at time zero when the chamber closes. Our results indicate that the flux estimated from a linear function can significantly underestimate CO₂ flux as compared with the exponential function. High spatial and temporal resolution soil CO₂ flux data obtained with our Multiplexing System in an agricultural field at the University of Nebraska Agricultural Experimental Station in Mead NE will be presented.

Key words: soil co₂ flux, exponential function, multiplexing system