Soil CO2 released effluxes of Birch forest in the Changbai Mountains.

Soils play a crucial role in the global carbon cycle.The exchange of CO2 between soils and the atmosphere is an ecosystem-scale flux.Nonetheless,our understanding of the exchange is still very limited.Temperate forest accounts for about 24% of the total forestland in the world.Thus,the contributions of CO2 from soil to atmosphere in this region can not be neglected in global carbon cycle.For this purpose,the investigations of CO2 exchange between soil and atmosphere were performed in birch forest in the Changbai Mountains in the northeast of China in autumn of 2002,spring and summer of 2003.The soil CO2 flux was measured by closed chamber and gas chromatography technique in the floor where the litters that cover the soil were removed or not removed.The result showed the soil carbon flux was higher in summer than that in spring and autumn.The litter layer influences the soil carbon release.In summer,the respiration flux of the litter layer-removed soil was higher than that of soil covered with litter layer,but the results were reverse in spring and autumn.Based on analysis of relationship between CO2 flux and temperature,the CO2 flux and temperature had significant relationship(P0.05).Four kinds of temperature were measured for the soil of 5㎝ depth,forestland surface,chamber and atmosphere.The coefficient of correlation between CO2 flux and the temperature of 5 cm depth soil was highest when the forestland surface was covered with litter layer.However,the coefficient of correlation between the flux and the forestland surface temperature was highest when the litter layer was removed from the floor.