HR: 1340h
AN: GC13B-1229    [Abstracts]
TI: Interactions Between Plant Growth and Soil Nutrient Cycling Under Elevated CO2: a Meta-Analysis.
AU: * de Graaff, M
EM: mdegraaff@ucdavis.edu
AF: University of California, One Shields Ave. Mail-Stop 1, Davis, CA 95616 United States
AU: * de Graaff, M
EM: mdegraaff@ucdavis.edu
AF: Wageningen University, Duivendaal 10, Wageningen, 6700 AA Netherlands
AU: van Groenigen, K
EM: kj.vangroenigen@wur.nl
AF: University of California, One Shields Ave. Mail-Stop 1, Davis, CA 95616 United States
AU: van Groenigen, K
EM: kj.vangroenigen@wur.nl
AF: Wageningen University, Duivendaal 10, Wageningen, 6700 AA Netherlands
AU: Six, J
EM: jwsix@ucdavis.edu
AF: University of California, One Shields Ave. Mail-Stop 1, Davis, CA 95616 United States
AU: van Kessel, C
EM: cvankessel@ucdavis.edu
AF: University of California, One Shields Ave. Mail-Stop 1, Davis, CA 95616 United States
AB: Free Air Carbon dioxide Enrichment (FACE) and Open Top Chamber studies (OTC) are valuable tools for evaluating the impact of elevated atmospheric CO2 on nutrient cycling in terrestrial ecosystems. Using meta-analytic techniques, we summarized the results of 105 studies on plant biomass production and soil organic matter dynamics in FACE and OTC experiments. The objective of the meta-analysis was to elucidate whether elevated CO2 alters nutrient cycling between plants and soil and if so, what the implications are for potential soil C sequestration under elevated CO2. Averaged over all studies, elevated CO2 stimulated above- and belowground plant biomass by 20% and 30%, respectively. Subsequently, microbial C contents and soil respiration increased by 17.3% and 7.5%, respectively. Despite the stimulation of microbial activity, soil C contents increased by 0.94% per year. However, when comparing experiments receiving both low and high N fertilization rates, plant growth and soil C contents increased only under elevated CO2 in experiments receiving the high N fertilization rates. Furthermore, N2 fixation was stimulated by elevated CO2 (+51%) only when additional mineral nutrient fertilizer was supplied. Elevated CO2 stimulated gross N immobilization by 22%, whereas gross and net N mineralization rates remained unaffected. In addition, the soil C:N ratio and microbial N contents increased under elevated CO2 by 3.8% and 6%, respectively. These results suggest that the main factor controlling the direction of the feedback between plant growth and soil nutrient cycling under elevated CO2 is nutrient availability; increased plant growth and soil C sequestration under elevated CO2 can only be sustained in the long-term when additional mineral nutrients are supplied. On the contrary, in unfertilized systems, elevated CO2 induces a negative feedback loop between plant growth and soil nutrient cycling by enhancing microbial N immobilization.
DE: 4806 Carbon cycling (0428)
DE: 4845 Nutrients and nutrient cycling (0470, 1050)
DE: 4850 Marine organic chemistry (0470, 1050)
SC: Global Climate Change [GC]
MN: Fall Meeting 2005