Saturday, 15 July 2006

Contributions of Corn Root Activities and Rhizosphere Soils to Total Carbon Dioxide Production.

Dong Chen1, C. Edward Clapp2, Jean-Alex E. Molina3, Antonio J. Palazzo4, Michael H.B. Hayes5, and Yi Zhang3. (1) California Dept of Water Resources, P.O. Box 942836, Sacramento, CA 94236-001, (2) USDA-ARS & Dept of Soil, Water and Climate, Univ of Minnesota, 1991 Upper Buford Circle, St. Paul, MN 55108, (3) Univ of Minnesota, Dept of Soil, Water and Climate, 1991 Upper Buford Circle, St. Paul, MN 55108, (4) USACOE, Cold Regions Research & Engineering Laboratory, Hanover, NH 03755, (5) Univ of Limerick, Foundation Building, Limerick, Ireland

In seeking the temperature increase effects on soil respiration, effects on contributions from plant root activities and bulk soil must be considered separately because their responses to the temperature increase are likely to be very different. Various root-exclusion methods have been used in the field to separately measure the carbon dioxides contributed by root activities and bulk soils. Our objective was to use an automated CO2 measurement system coupled with a root-exclusion method to measure soil CO2 concentrations in rooted and root-excluded soils with a high temporal resolution. A 0.75 by 1.25 m area was isolated from a 6 by 9 m corn plot by burying two layers of plastic film sandwiching a layer of aluminum film to a depth 0.9 m. Six CO2 transmitters, TDR, and thermistors were installed at depths of 10 to 60 cm with a interval of 10 cm inside and outside the isolated area, and two more CO2 transmitters near the soil surface. No corn was planted inside the isolated area and outside corn roots could not be extended into the isolated area. The measured CO2 concentrations in root-excluded soils were consistently lower than in rooted soil at all measured depths over the growing season. High temporal resolutions of soil CO2, temperature, and moisture over depth permit computation of CO2 production over depths of both rooted and root-excluded soils. The difference between CO2 productions of rooted and root-excluded soil can be considered as a contribution of corn roots.

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