The Study On The Energy And CO₂ Flux Variations In An Evergreen And Deciduous Broad-leaved Mixed Forest In Tianmu Mountain

Based on the measurements with open-path eddy covariance system and meteorological instruments in an evergreen and deciduous mixed hardwood forest of Tianmu Mountain,we ovserved the data from July 2014 to June 2015.we calculate the value of NEE?RE and RE,analysed the change characteristics of energy flux and balance meanwhile.The study contributed to the the research of carbon cycle of forest ecosystem and the understanding of carbon sink of forests.The results indicated:?1?The ecosystem played role of a carbon sink except for January(1.483 g C·m^-2).The average monthly net ecosystem exchange were-62.626 g C·m^-2,the monthly carbon sequestration showed a double-peak curve,the maximum carbon sink was-126.78 g C·m^-2,occurred in June,then in May.The net ecosystem exchange?NEE?had typical seasonal characteristics at the time point of positive and negative conversion.The yearly net ecosystem exchange?NEE?,gross ecosystem exchange?GEE?and ecosystem respiration?RE?,were-751.515 gC·m^-2·a-1,-1694.38 gC·m^-2·a-1? 942.864 gC·m^-2·a-1??2?The results showed that: the yearly Rn?net radiation??H?latent heat flux??LE?the sensitive flux heat?and G?soil heat flux?were 3142.15 MJ·m^-2,1470.34 MJ·m^-2,1339.01 MJ·m^-2,40.33 MJ·m^-2 respectively.The diurnal variations of energy balance components existed on expected single peaks.The sensible ?latent and soil heat fluxes almost have 46.8% ?42.6% and 1.3% of the net radiation,respectively.Monthly variation of the Bowen ratio exist big fluctuation,the yearly enrgy balance closure of the ecosystem was 0.91,and the mean monthly averge was 0.98.?3?The maximal value of soil heat flux was 12.632 MJ·m^-2,occurred in June,the minimal value occurred in December(-13.8233 MJ·m^-2).The yearly soil heat flux was 40.33MJ·m^-2,soil is the sink of heat.The regression between soil heat flux and net radition showed that the feedback of the soil heat flux lagged 2h behind the net radiation,The regression showed that soil heat flux was significantly?P<0.0001?related to temperature at both half an hour and daytimes,and the coefficient of correlation in monthly scale?0.557?was greater than that in half an hour scale.The coefficient of correlation in monthly scale?daily scale and half an hour scale were 0.551,0.347,0.217 respectively.