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

基于Forest-DNDC的长白山阔叶红松林土壤碳氮温室气体通量的模拟研究（英文）

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.

土壤温室气体排放是土壤与大气之间的温室气体交换的重要途径,但对土壤温室气体排放动态变化的理解和收支水平的估算仍存在较大的不确定性。基于动态箱原位监测的高频、连续土壤温室气体通量数据,本研究初步检验了生物地球化学模型(Forest-DNDC)对长白山阔叶红松林(CBF)土壤CH_4、CO_2和N_2O温室气体通量的模拟效果。结果显示,当前版本的Forest-DNDC可以反演得到土壤温度、土壤湿度和积雪等主要环境要素的总体变化趋势,但是对于环境要素季节变化的准确模拟尚存在较明显偏差,特别是在非生长季节。模拟得到的土壤CH_4通量与监测结果相当接近,并且受到了土壤温度和积雪变化的显著调控。受温度变化的影响,模拟CO_2通量的季节变化与测定值相似,均在夏季达到高峰,但模拟的土壤CO_2排放量明显小于实际测定结果。与监测的土壤N_2O通量在春季冻融期间出现排放高峰的变化显著不同的是,模拟土壤N_2O通量主要受温度变化的影响,其最大值出现在夏季。因此,有必要结合更长时段的土壤温室气体监测数据,进一步优化模型参数与过程,特别是土壤水热传导和温室气体的产生过程等,为模拟改进和生态系统碳氮收支评估,以及从站点到区域的扩展提供支撑。