Study On Dynamics Of CO₂Fluxes In Tobacco Field Ecosystem And Environmental Impact Factors In Enshi

Study on the carbon emissions has become focus of global change. As ane ecological system ofhigh artificial intervention, farmland is increasingly concerned by people. Tobacco is an importanteconomic crop, but the carbon fluxes in tobacco field ecosystem are seldom studied both at home andabroad. In order to study change of the carbon fluxes in tobacco field ecosystem and fill up the field intobacco industry, variations of CO₂emission fluxes in a flue-cured tobacco field at harvest period underdifferent organic fertilizer treatments were measured by the closed chamber-infrared method. Theeffects of partial replacement of chemical fertilizer with organic fertilizers, and humiture on carbonemission fluxes were also discussed. The main results were as follows:（1） CO₂emission fluxes from tobacco field ecosystem all showed wavy diurnal change. Thebiggest net carbon assimilation in tobacco harvest period was at11:30～15:30, while the biggestemitters was in the evening before all leaves were harvested. The maximum fluxes of carbon emissionswent forward from19:30during the tobacco harvest process. Carbon fluxes and soil carbon fluxesshowed the same trend after all tobacco leaves were harvested.（2） CO₂emission fluxes from tobacco field soil had obviously diurnal variation, which werepresented in single-apex or double-apex ones. The maximum emission flux was appeared at about11:30.Dynamic changes in carbon fluxes were consistent with air temperature and soil temperature changes.CO₂emission fluxes of tobacco field ecosystem mainly came from net photosynthesis of tobacco, butnot from soil respiration. There was no significant difference in soil carbon fluxes between daily meanand9^-11points of the same day.（3） Carbon fluxes in tobacco field ecosystem changed from assimilation to emission and mainlyshowed in carbon emission during the observation period, The biggest net carbon assimilation appearedbefore harvest. Tobacco soil carbon fluxes increased first and decreased afterwards. The maximumemission fluxes wree138.6～161.9mg·m^-2·h^-1, while the minimum48.7～51.2mg·m^-2·h^-1.（4） The order of different processing on carbon fluxes in tobacco fields ecosystem was JF＞YG＞CB＞MW. Carbon fluxes of tobacco stems fertilizer and JinFengYe organic fertilizer were significantlyhigher than that with other treatments in the observation period. MeiWang organic fertilizer treatmentwas significantly lower than the other three treatments. In view of greenhouse gas emissions, the mostenvironmental choice was MeiWang organic fertilizer. The order of different processing on carbonfluxes from tobacco field soil was JF＞CB＞YG＞MW, JinFengYe organic fertilizer promoted CO₂emission fluxes in the tobacco soil significantly. The order of different processing on carbon fluxes fromtobacco was YG＞JF＞CB＞MW.（5） From the point of the harvest period, carbon fluxes were not significantly correlated with airtemperature, surface temperature,5cm and10cm soil temperature, But it was discovered thatecosystem CO₂emission fluxes were significantly correlated with number of leaves. Air temperatureshowed best agreement with soil carbon fluxes. （6） It was predicted by the models established in this study that throughout the harvest period thatpure chemical fertilizer and conventional treatment soil CO₂emission fluxes in turn were79.6,70.9gCO₂-C·m^-2, while ecosystem CO₂emission fluxes in turn were35.2,60.5g CO₂-C·m^-2.