Biases of chamber methods for measuring soil CO₂ efflux demonstrated with a laboratory apparatus.

Abstract

Investigators have historically measured soil CO₂ efflux as an indicator of soil microbial and root activity and more recently in calculations of carbon budgets. The most common methods estimate CO₂ efflux by placing a chamber over the soil surface and quantifying the amount of CO₂ entering the chamber per unit area of soil per unit time. Schlesinger (1977), Anderson (1982), Rolston (1986a), Raich and Nadelhoffer (1989), and Nakayama (1990) have reviewed various chamber methods. No single method is established as a standard (Anderson 1982, Nakayama 1990, Norman et al. 1992), partly because methods are not compared to known effluxes (Nakayama 1990). Past comparisons have only shown a method to be higher or lower than another method.

This study compared the responses of two commonly used chamber methods to known effluxes from the surface of a simulated soil. Our known effluxes are based on calculations using Fick's law of diffusion. The two methods we tested were a static-chamber method with soda lime as a CO₂ absorbent and a dynamicchamber method consisting of an infrared gas analyzer in a closed air-circulation loop. Because the absorption rate of alkali materials used in static chambers is thought to be a source of bias (Freijer and Bouten 199l, Nakadai et al. 1993), we were also interested in how the soda-lime absorbent affected the headspace CO₂ concentration of the static chambers.

Citation

Nay, S. Mark; Mattson, Kim G.; Bormann, Bernard T. 1994. Biases of chamber methods for measuring soil CO₂ efflux demonstrated with a laboratory apparatus. Ecology. 75(8): 2460-2463