Abstract: Based on the localized near field (LNF) theory and coupled with the distribution of vertical velocity standard deviation (σw(z)) and Lagrangian integral time scales (TL(z)) within the canopy proposed by Raupach,the relationship between water vapor source/sink distribution and its mean concentration profile was constructed.The estimation of forest evapotranspiration was also conducted by the inverse Lagrangian dispersion analysis,which can calculate the water vapor source/sink distribution from its mean concentration profile.The calculated forest evapotranspiration was compared with the measured values.It was concluded that the simulated precision of the daily daytime evapotranspiration could reach 87.3%,the calculated results was 15%～25% higher than the measured one,the nighttime evapotranspiration was about 70% of the daily value,and the total monthly evapotranspiration from June to August was higher than that in May and September.

Key words: Soil carbon/nitrogen cycle, Carbon density, Nitrogen cycle, C/N ratio