Estimating respiration of roots in soil: interactions with soil CO2, soil temperature and soil water content


Bouma, T.J.; Nielsen, K.L.; Eissenstat, D.M.; Lynch, J.P.


Plant and Soil, Volume 195, Issue 2, p.221-232 (1997)

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An automated, open, gas-exchange system was designed that allows continuous measurements in 12 chambers with intact roots in soil. By using three distinct chamber designs, each with a different path for the air flow, it was possible to measure root respiration over a range of soil CO 2 concentrations between 400 and 25000 ppm and to separate the effect of irrigation on observed and actual root respiration rate in studies with one-year-old Citrus volkameriana seedlings. Root respiration was strongly affected by diurnal fluctuations in temperature, which agrees well with the literature, but was not affected by soil CO 2 concentrations. Soil CO 2 was strongly affected by soil water content but not by respiration, unless the air flow for root respiration measurements was directed through the soil. The latter method of measuring root respiration reduced soil CO 2 concentration to that of incoming air. Irrigation caused a temporary reduction in CO 2 diffusion, decreasing the observed respiration rates obtained by techniques that depended on diffusion. This apparent drop in respiration rate did not occur if the air flow was directed through the soil.