Modelling Soil Greenhouse Gas Fluxes from a Broad-Leaved Korean Pine Forest in Changbai Mountain: Forest-DNDC Model Validation

Abstract

Fluctuations in soil greenhouse gas (GHG) are an important part of the terrestrial ecosystem carbon-nitrogen cycle, but uncertainties remain about the dynamic change and budget assessment of soil GHG flux. Using high frequency and consecutive soil GHG fluxes measured with an automatic dynamic chamber system, we tested the applicability of the current Forest-DNDC model in simulating soil CH4, CO2 and N2O fluxes in a temperate broad-leaved Korean pine forest at Changbai Mountain. The results showed that the Forest-DNDC model reproduced general patterns of environmental variables, however, simulated seasonal variation in soil temperature, snow melt processes and soil moisture partly deviated from measured variables, especially during the non-growing season. The modeled CH4 flux was close to the field measurement and co-varied mainly with soil temperature and snowpack. The modeled soil CO2 flux had the same seasonal trend to that of the observation along with variation in temperature, however, simulated CO2 flux in the growing season was underestimated. The modeled N2O flux attained a peak in summer due to the influence of temperature, which was apparently different from the observed peak of N2O flux in the freeze-thaw period. Meanwhile, both modeled CO2 flux and N2O flux were dampened by rainfall events. Apart from consistent estimation of annual soil CH4 flux, the annual accumulation of CO2 and N2O was underestimated. It is still necessary to further optimize model parameters and processes using long-term high-frequency observation data, especially transference of heat and water in soil and GHG producing mechanism. Continues work will improve modeling, ecosystem carbon-nitrogen budget assessment and estimation of soil GHGs flux from the site to the region.