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Determining Root Activity Distribution by Measuring Surface Carbon Dioxide Fluxes

Jacob Blaustein Inst. for Desert Research, Ben Gurion Univ. of the Negev, Sede Boqer Campus, 84990, Israel

G. E. Cardon and C. J. Phene

USDA-ARS Water Management Research Lab., 2021 S. Peach Ave., Fresno, CA 93727

D. Peters, D. E. Rolston and J. W. Biggar

Land, Air, and Water Resources, Univ. of California, Davis, CA 95616

*Corresponding author.

ABSTRACT

Methods for determining root characteristics and distributions are time consuming and tedious. Indirect approaches could decrease the effort required to obtain information on root distributions. The objectives of this study were to measure soil surface CO₂ flux and to relate these measurements to root properties. Two chambers to measure CO₂ fluxes at the soil surface were tested for use in root activity studies. One chamber was a 0.75-L cylinder and the other was a 7.1-L cubic chamber. The bottom edges of both chambers were inserted 1 to 2 cm into the surface soil. The increase in CO₂ concentration in the chambers was measured with infrared gas analyzers. The following were used to evaluate the applicability of the approach for root studies: (i) test of the relationship between CO₂ surface fluxes and root characteristics (length, area, mass, and number) in the root zone of a mature almond (Prunus amigdalus Batsch. cv. Butte) orchard and a corn (Zea mays L.) field, and (ii) evaluation of temperature and solar radiation effects on CO₂ soil surface flux. The results showed that surface CO₂ fluxes were proportional to the logarithm of root characteristics, i.e., large changes in root characteristics were associated with small changes in flux. Soil temperature had a distinct effect on measured CO₂ surface flux. There was a clear diurnal cycle for soil surface CO₂ flux, which peaked near solar noon and maximum solar radiation. Acceptable correlations between the major root characteristics and surface CO₂ flux suggest that this approach can provide vital information on root activity.

Received for publication October 7, 1992.