Oecologia
ISSN: 0029-8549 (printed version)
Abstract Volume 127 Issue
2 (2001) pp 153-165
Elevated CO2,
litter chemistry, and decomposition: a synthesis
Richard J. Norby (1), M. Francesca
Cotrufo (2), Philip Ineson (3), Elizabeth G. O'Neill (1), Josep G. Canadell
(4)
(1) Environmental Sciences Division,
Oak Ridge National Laboratory, Bldg. 1059, PO Box 2008, Oak Ridge, TN 37831-6422
USA E-mail:
Received: 28 December 1999 / Accepted:
21 November 2000 / Published online: 2 February 2001
Abstract. The results of
published and unpublished experiments investigating the impacts of elevated
[CO2] on the chemistry of leaf litter and
decomposition of plant tissues
are summarized. The data do not support the hypothesis that changes in
leaf litter chemistry often associated with
growing plants under elevated
[CO2] have an impact on decomposition processes. A meta-analysis of data
from naturally senesced leaves in
field experiments showed that
the nitrogen (N) concentration in leaf litter was 7.1% lower in elevated
[CO2] compared to that in ambient
[CO2]. This statistically significant
difference was: (1) usually not significant in individual experiments,
(2) much less than that often observed in
green leaves, and (3) less in
leaves with an N concentration indicative of complete N resorption. Under
ideal conditions, the efficiency with
which N is resorbed during leaf
senescence was found not to be altered by CO2 enrichment, but other environmental
influences on resorption
inevitably increase the variability
in litter N concentration. Nevertheless, the small but consistent decline
in leaf litter N concentration in many
experiments, coupled with a 6.5%
increase in lignin concentration, would be predicted to result in a slower
decomposition rate in CO2-enriched
litter. However, across the assembled
data base, neither mass loss nor respiration rates from litter produced
in elevated [CO2] showed any
consistent pattern or differences
from litter grown in ambient [CO2]. The effects of [CO2] on litter chemistry
or decomposition were usually
smallest under experimental conditions
similar to natural field conditions, including open-field exposure, plants
free-rooted in the ground, and
complete senescence. It is concluded
that any changes in decomposition rates resulting from exposure of plants
to elevated [CO2] are small
when compared to other potential
impacts of elevated [CO2] on carbon and N cycling. Reasons for experimental
differences are considered,
and recommendations for the design
and execution of decomposition experiments using materials from CO2-enrichment
experiments are
outlined.
Keywords. Decomposition ·
Elevated atmospheric CO2 · Lignin · Litter quality ·
Meta-analysis · Nitrogen
Article
in PDF format (120 KB)
Online publication: April 10, 2001
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