The Role of Soil Organic Matter and Manures in Sustainable Nutrient Cycling - Sustainable Management of Soil Organic Matter - page 301

H.A.Torbertet al. Effect of Elevated CO 2 and Temperature

4.11

Effect of Elevated CO 2
and Temperature on Soil C
and N Cycling

H.A. T ORBERT 1 , S.A. P RIOR 2

AND H.H. R OGERS 2

1
USDA-ARS Grassland, Soil and Water Research Laboratory,
808 EastBlacklandRoad, Temple, TX 76502; and 2 USDA-ARS
National Soil Dynamics Laboratory, 411 South Donahue Drive,
Auburn, AL 36832, USA

Introduction

One potential and highly debated implication of global change is an
alteration in the dynamics of soil C in terrestrial ecosystems (Rogers et al .,
1999). This potential change in soil C dynamics is important not only
because of a possible mitigating effect on rising atmospheric CO 2 concen-
tration, but also because of its influence on quality of soil organic matter.
Ultimately, the rate and extent of turnover of organic C produced in an
elevated CO 2 environment will control C storage in terrestrial ecosystems
(Van Veen et al ., 1991).
The decomposition of crop residue inputs is a fundamental component
in the turnover of soil organic C which is dependent on several crop,
soil, management (i.e. tillage practices) and climatic factors (Potter et al .,
1998). Plant factors controlling decomposition such as age, size, chemical
composition and residue C : N ratio (Ghidey and Alberts, 1993) may be
affected by changing CO 2 level (Torbert et al ., 1995; Prior et al ., 1997a).
Research considering the effect of elevated CO 2 on crop residue decompo-
sition suggests that CO 2 -enriched cropping systems may store more soil C
(Torbert et al ., 1995, 1998; Prior et al ., 1997b). Even if decomposition
rates of plant components (produced under elevated CO 2 ) are not changed,
residue decomposition products may impact soil N dynamics (Torbert
et al ., 1995, 1996, 1998).
Residue decomposition is a microbial-driven process and soil tempera-
ture is an important factor controlling decomposition, thereby influencing
soil C dynamics. Thus, potential changes in soil temperature due to global