HR: 16:45h
AN: B32D-04 [PDF]
TI: Decomposition of $^{14}$C-Labeled Roots in a Pasture Soil Exposed to 10 Years of Elevated
CO$_{2}$
AU: van Groenigen, K
EM: Kees.JanvanGroenigen@wur.nl
AF: Department of Agronomy and Range Science, One Shields Avenue
University of California, Davis, CA 95616 United States
AU: van Groenigen, K
EM: Kees.JanvanGroenigen@wur.nl
AF: Laboratory for Soil Science and Geology, Wageningen University, Wageningen, 6700 AA
Netherlands
AU: van Groenigen, K
EM: Kees.JanvanGroenigen@wur.nl
AF: Alterra, Soil Science Center, P.O. Box 47, Wageningen, 6700 AA
Netherlands
AU: Gorissen, T
EM: ton.gorissen@wur.nl
AF: Plant Research International, Wageningen University, Wageningen, 6700 AA
Netherlands
AU: * Six, J
EM: jwsix@ucdavis.edu
AF: Department of Agronomy and Range Science, One Shields Avenue
University of California, Davis, CA 95616 United States
AU: Harris, D
EM: dharris@ucdavis.edu
AF: Stable Isotope Facility, One Shields Avenue
University of California, Davis, CA 956161 United States
AU: Kuikman, P
EM: peter.kuikman@wur.nl
AF: Alterra, Soil Science Center, P.O. Box 47, Wageningen, 6700 AA
Netherlands
AU: van Groenigen, J
EM: janwillem.vangroenigen@wur.nl
AF: Alterra, Soil Science Center, P.O. Box 47, Wageningen, 6700 AA
Netherlands
AU: van Kessel, C
EM: cvankessel@ucdavis.edu
AF: Department of Agronomy and Range Science, One Shields Avenue
University of California, Davis, CA 95616 United States
AB:
The net storage of soil C is determined by the balance between microbial decomposition rates and soil C input, both of which
might be altered under prolonged elevated atmospheric CO$_{2}$. Here we report on a study to determine the effect of elevated
CO$_{2}$ on root mineralization through changes in substrate quality, and the subsequent soil microbial response.
$^{14}$C-labeled {\it Lolium perenne} root material, produced under ambient and elevated CO$_{2}$ was incubated in soil for
64 days. The soils used for the incubation had been exposed to ambient and elevated CO$_{2}$ under FACE-conditions for 10
years. Fertilizer N was applied at a rate of 140 and 560 kg N ha$^{-1}$ yr$^{-1}$ and the CO$_{2}$ concentration was
increased to 60 Pa pCO$_{2}$. {\it Lolium perenne} root material grown under elevated CO$_{2}$ significantly decreased
microbial respiration in high N soils, whereas it enhanced microbial C assimilation in low N soils. The amount of
$^{14}$CO$_{2}$ respired per amount of $^{14}$C incorporated in the microbial biomass was significantly lower for high
CO$_{2}$ roots compared to low CO$_{2}$ roots. We suggest that this is the result of an increased fungal:bacterial ratio,
causing an increased metabolic efficiency. Soils exposed to elevated CO$_{2}$ respired more native SOC, both with and without
the addition of the root material. During the first stage of the incubation experiment, root material decomposed slower in
high CO$_{2}$ soils. Overall, the addition of root material decreased the decomposition of native SOC, thus causing a
negative priming effect. Our results suggest that priming effects might obscure CO$_{2}$ data in incubation experiments in
which unlabeled substrate is applied. From the results obtained, we suggest that limited net C storage might occur through a
slower turnover of root material grown under elevated CO$_{2}$
DE: 1615 Biogeochemical processes (4805)
SC: Biogeosciences [B]
MN: 2003 Fall Meeting