Daly,E., Palmroth,S., Stoy,P., Siqueira,M., Oishi,A.C., Juang,J.-Y., Oren,R., Porporato,A. and Katul,G.G.(2009): The effects of elevated atmospheric CO2 and nitrogen amendments on subsurface CO2 production and concentration dynamics in a maturing pine forest. Biogeochemistry, 94, 271-287.

『成長したマツ林における地下の二酸化炭素生産と濃度に対する上昇した大気中二酸化炭素と窒素改善の影響』

『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 [CO2]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 CO2 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.

Keywords: Soil CO2 dynamics; Climate change; Elevated atmospheric CO2; Nitrogen deposition; Fertilization; Loblolly pine』

Introduction
Methods
　Site description
　Measurements
　Data processing
　Statistical analyses
　CO2 fluxes and production
Results and discussion
　Subsurface CO2 concentrations
　　Effects of the treatments
　　C dynamics at different depths and time-scales
　　Rainfall-induced variation in C near the soil surface
　CO2 production and fluxes
　　Effect of the treatments
　　Soil CO2 storage
　　Vertical distribution and dynamics of CO2 fluxes and production
　　Limitations to comparisons between direct measurements and indirect estimates of CO2 flux
Conclusions
Acknowledgments
References

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