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 freq...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.展开更多
Pit and mound micro-relief(resultant microsites from trees uprooted by windthrow) could have regimes of microclimate and soil features that differ from areas of undisturbed soil. In an attempt to provide a comprehensi...Pit and mound micro-relief(resultant microsites from trees uprooted by windthrow) could have regimes of microclimate and soil features that differ from areas of undisturbed soil. In an attempt to provide a comprehensive evaluation of the significance of pits and mounds on soil features and also the dynamics of greenhouse gas(GHG) fluxes at local scale, this study was carried out in a reserved area of Darabkola forest in Mazandaran Province, northern Iran. The age of a pit and mound was considered equal to the degree of decay of the blown down tree. Three microsites were distinguished, consisting of pit bottom(PB), mound top(MT) and undisturbed area(UA). Soil samples were taken at 0–15 and 15–30 cm depths from all microsites and analysed for soil physical, chemical and biological features. Our findings suggested that in context of forest ecology, pits and mounds following windthrow events should be considered as an effective factor influencing soil features(i.e., density, texture, water content, p H, organic C, total N, available nutrients and earthworm density/biomass) and especially GHG fluxes. Results showed that MT acted as a sink for N2O(-0.010 mg N2 O m-2d-1) and CH4(-0.257 mg CH4m-2d-1) fluxes and also produced lower CO2 concentrations(0.095 mg CO2 m-2d-1) than PB(0.207 mg CO2 m-2d-1) and UA(0.098 mg CO2 m-2d-1). As a consequence, a separation into pits/mounds would be important for a precise budgeting of greenhouse gases.展开更多
基金National Key Research and Development Program of China(2017YFC0503801)National Natural Science Foundation of China(31570446)
文摘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.
文摘Pit and mound micro-relief(resultant microsites from trees uprooted by windthrow) could have regimes of microclimate and soil features that differ from areas of undisturbed soil. In an attempt to provide a comprehensive evaluation of the significance of pits and mounds on soil features and also the dynamics of greenhouse gas(GHG) fluxes at local scale, this study was carried out in a reserved area of Darabkola forest in Mazandaran Province, northern Iran. The age of a pit and mound was considered equal to the degree of decay of the blown down tree. Three microsites were distinguished, consisting of pit bottom(PB), mound top(MT) and undisturbed area(UA). Soil samples were taken at 0–15 and 15–30 cm depths from all microsites and analysed for soil physical, chemical and biological features. Our findings suggested that in context of forest ecology, pits and mounds following windthrow events should be considered as an effective factor influencing soil features(i.e., density, texture, water content, p H, organic C, total N, available nutrients and earthworm density/biomass) and especially GHG fluxes. Results showed that MT acted as a sink for N2O(-0.010 mg N2 O m-2d-1) and CH4(-0.257 mg CH4m-2d-1) fluxes and also produced lower CO2 concentrations(0.095 mg CO2 m-2d-1) than PB(0.207 mg CO2 m-2d-1) and UA(0.098 mg CO2 m-2d-1). As a consequence, a separation into pits/mounds would be important for a precise budgeting of greenhouse gases.
