Separating Soil Respiration into Plant and Soil Components Using Analyses of the Natural Abundance of Carbon-13
- P. Rochette *a,
- L. B. Flanaganb and
- E. G. Gregorichc
- a Agriculture and Agri-Food Canada, Soils and Crops Research and Development Centre, 2560 Hochelaga Blvd., Ste-Foy, QC, Canada G1V 2J3
b Dep. of Biological Sciences, Univ. of Lethbridge, 4401 University Dr., Lethbridge, AB, Canada, T1K 3M4
c Agriculture and Agri-Food Canada, Eastern Cereal and Oilseed Research Centre, Neatby Bldg., Central Experimental Farm, Ottawa, ON, Canada, K1A 0C6
In presence of vegetation, the CO2–C produced by respiration activity in soils originates from plant C (rhizosphere respiration, R rh) and from soil C (soil respiration, R s). Quantitative estimates of the CO2 produced by each source are required in many studies of C dynamics in the soil–plant system. In this study, we (i) used measurements of the 13C value of soil CO2 to separate total soil respiration (R t) into subcomponents R rh and R s in a maize (Zea mays L.) field under undisturbed conditions and (ii) compared these R rh estimates with values obtained using the root-exclusion approach. The maximum contribution of R rh to total respiration was 45%, observed in August. Estimates of R rh increased from zero 30 d after planting to 2 g CO2–C m−2 d−1 70 d after planting, remained relatively constant at that level in August, and then decreased until the end of the growing season. The total C losses as R rh were 17% of the crop net assimilation. Estimates of R s gradually declined from 3.3 g CO2–C m−2 d−1 in late June to 1.4 g CO2–C m−2 d−1 at the end of the season. Losses of soil C represented ≈6% of total soil C. Variable values of δ13C of the soil CO2 in the control plot after Day 250 made the technique less reliable late in the season. However, several observations indicated that the approach has potential to provide quantitative estimates of R rh and R s First, the seasonal pattern of the R rh estimates coincided with that of the plant growth and physiological activity. Second, the cumulated R rh across the growing season agreed well with published data obtained using 14C labeling techniques. Third, in the maize plot, variation in the estimated R s was closely correlated with changes in soil temperature with a Q 10 of 1.99 Finally, the estimates of R rh obtained using the isotopic approach agreed well with those obtained using the root exclusion technique.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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