Detrmination of Stable Carbon Isotope Composition of Atmospheric Methane by Precon-GC/C-IRMS System Method Relations between Stable Carbon Isotope Discrimination and Water Use Efficiency as well as Growth for Poplar Distribution characteristics of soil humus fractions stable carbon isotope natural abundance (δ13C) in paddy field under long-term ridge culture. Variations of CO2 concentration and δ13C and influencing factors of Quercus variabilis plantation in low hilly area of North China.