Abstract
Profiles of subsurface soil CO2 concentration, soil temperature, and soil moisture, and throughfall were measured continuously during the years 2005 and 2006 in 16 locations at the free air CO2 enrichment facility situated within a temperate loblolly pine (Pinus taeda L.) stand. Sampling at these locations followed a 4 by 4 replicated experimental design comprised of two atmospheric CO2 concentration levels (ambient [CO 2]a, ambient + 200 ppmv, [CO2]e) and two soil nitrogen (N) deposition levels (ambient, ambient + fertilization at 11.2 gN m-2 year-1). The combination of these measurements permitted indirect estimation of belowground CO2 production and flux profiles in the mineral soil. Adjacent to the soil CO 2 profiles, direct (chamber-based) measurements of CO2 fluxes from the soil-litter complex were simultaneously conducted using the automated carbon efflux system. Based on the measured soil CO2 profiles, neither [CO2]e nor N fertilization had a statistically significant effect on seasonal soil CO2, CO2 production, and effluxes from the mineral soil over the study period. Soil moisture and temperature had different effects on CO2 concentration depending on the depth. Variations in CO2 were mostly explained by soil temperature at deeper soil layers, while water content was an important driver at the surface (within the first 10 cm), where CO2 pulses were induced by rainfall events. The soil effluxes were equal to the CO2 production for most of the time, suggesting that the site reached near steady-state conditions. The fluxes estimated from the CO2 profiles were highly correlated to the direct measurements when the soil was neither very dry nor very wet. This suggests that a better parameterization of the soil CO2 diffusivity is required for these soil moisture extremes.
Original language | English (US) |
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Pages (from-to) | 271-287 |
Number of pages | 17 |
Journal | Biogeochemistry |
Volume | 94 |
Issue number | 3 |
DOIs | |
State | Published - Jul 2009 |
Externally published | Yes |
All Science Journal Classification (ASJC) codes
- Environmental Chemistry
- Water Science and Technology
- Earth-Surface Processes
Keywords
- Climate change
- Elevated atmospheric CO
- Fertilization
- Loblolly pine
- Nitrogen deposition
- Soil CO dynamics