HR: 10:35h
AN: B52A-02    [Abstracts]
TI: Quantifying the combined effects of elevated atmospheric CO2 and nutrient amendments on subsurface CO2 production in a southern Loblolly pine plantation using Inverse Methods
AU: * Daly, E
EM: edaly@pratt.duke.edu
AF: Department of Civil and Environmental Engineering, Duke University, Hudson Hall, Durham, NC 27708 United States
AU: * Daly, E
EM: edaly@pratt.duke.edu
AF: Nicholas School of the Environment and Earth Sciences, LSRC, Durham, NC 27708 United States
AU: Porporato, A
EM: amilcare@duke.edu
AF: Department of Civil and Environmental Engineering, Duke University, Hudson Hall, Durham, NC 27708 United States
AU: Porporato, A
EM: amilcare@duke.edu
AF: Nicholas School of the Environment and Earth Sciences, LSRC, Durham, NC 27708 United States
AU: Oren, R
EM: ramoren@duke.edu
AF: Nicholas School of the Environment and Earth Sciences, LSRC, Durham, NC 27708 United States
AU: Katul, G
EM: gaby@duke.edu
AF: Department of Civil and Environmental Engineering, Duke University, Hudson Hall, Durham, NC 27708 United States
AU: Katul, G
EM: gaby@duke.edu
AF: Nicholas School of the Environment and Earth Sciences, LSRC, Durham, NC 27708 United States
AB: Subsurface CO_2 production (S), one of the largest CO_2 sources to the atmosphere, has been the subject of intense studies because of its potential role in amplifying global warming. Projected warming trends associated with rise in atmospheric CO_2 can lead to higher soil temperature and greater S thereby completing the positive feedback.Surprisingly, the individual and combined effects of elevated atmospheric CO_2 and nitrogen deposition rates on S remain poorly understood, especially in forested ecosystems. Field studies on the effects of elevated atmospheric CO_2 on S are mixed with several studies reporting an increase in S because of an increase in root biomass and enhanced microbial activity, while others reporting only transient changes. On the other hand, several field experiments documented a clear suppression of S with increased nitrogen amendments. Resolving the combined effects of elevated atmospheric CO_2 and nitrogen amendments on S is complicated by an intricate balance between various physical and biological processes. To begin confronting this problems, frequent in situ measurements of root and microbial respiration at multiple soil depths and at the same location must be conducted. Here, we quantify the joint and individual effects of elevated atmospheric CO_2 and nutrient amendments on CO_2 production rates in the soil pore spaces within the root-zone using a combination of field measurements and inverse modeling* across a wide range of soil moisture states. The field experiment utilizes the Free Air CO_2 Enrichment facility in which 30 m rings enriched with CO_2 are also fertilized. The inverse model calculations use an array of small solid-state CO_2 sensors for measured spatial concentration distributions along with measured soil moisture and soil temperature to estimate gas-phase CO_2 diffusivity. Implications to below ground carbon cycling and their linkages to alterations in root-water uptake patterns due to elevated CO_2 and N are also discussed.
DE: 0428 Carbon cycling (4806)
DE: 1813 Eco-hydrology
SC: Biogeosciences [B]
MN: Fall Meeting 2005